A Clayton's Sticky

Bob Hart · June 30th, 2007, 08:52 AM

My original posts have sunk fairly deep by now into the chasms of post past.

Here following below are re-posts of some which have also been updated to reflect more recent experiences.

Please do not blindly read and follow the practices described as I am neither the inventor of the Letus35, nor a continous user of the appliance.

There may be unintended consequences of injury to the operator of the Letus35/Camera combination and damage to the appliance and attached camera.

Owners of the Letus35/camera combination can and are advised to choose not to apply any of the methods and practices described in the following posts, but to conduct their own researches into the appliances and their proper and safe use.

The consequences of any adjustments or use of the methods decribed by me therefore remain the responsibility of the owner/operator alone.

These notes are published in hope of being some assistance to new owners until such time as the manufacturer is able to publish a handbook.

Bob Hart · June 30th, 2007, 08:55 AM

NON-AUTHORISED OPERATOR INSTRUCTIONS.

LETUS35 FLIP MOTION PICTURE FILM EMULATOR FOR THE CANON XL FAMILY OF CAMCORDERS.

FOREWORD:

Letus35 users are warned that whilst following this instruction set may assist yield satisfactory results, there may be outcomes and damages to equipment which are unexpected.

This comment does not reflect any shortcoming or otherwise on the Letus35 systems or other groundglass based image relay systems but assumes possible incompetences of this author.

Readers of this instruction set are strongly advised to proactively confirm or refute these suggestions by independent reading, consultation with other persons and research :-

INTRODUCTION.

The Letus35 Flip is an erecting non-coherent image relay device which enables popular full frame capable Nikon F Mount and Canon Mount 35mm camera lenses to be fitted to the camcorder, yet achieve nearer to the same fields of view available to the still photographer or motion picture film camera operator.

The 35mm motion picture image frame is the most closely emulated.

This facility enables the camcorder operator to replicate the available narrow depth of field and perspective effects normally associated with the larger available imaging area of 35mm film for a given lens focal length.

In addition, the indirect relay of the image via a groundglass screen confers an image aesthetic more in common with motion picture film images.

A feature of the LETUS35 family of adaptors is the unique groundglass motion system.

The design confers self-counterbalancing of the entire moving structure. Two stages of rubber support coupling isolate the moving structure from the casework. Any vibration is caused only by passive structural resistance to the motion by the necessary support of the moving structure and not by direct imposition of torque or mass-reaction loads.

HANDLING.

The Letus35, should be treated with the due care normal for optical instruments. Avoid sharp impacts, extremes of temperature, especially rapid changes, dust and rainfall. The Letus35 should ideally be transported in its own padded case in a supporting profile in the manner of other optical products and cameras.

Unless in actual use in a mobile environment, transport of the assembled camcorder/Letus35 combination, as for the normal camcorder/genuine Canon lenses combination, is not recommended. The lens mount may be subjected to abnormal stress in this circumstance.

The “flip” or erecting component of the optical path consists of surface coated mirrors, chosen for least light loss and less weight. They are mounted in a stout, precisely machined, plastic case.

The mirrors are fixed into the flip enclosure with non-hardening silicon adhesive which provides firm mounting with some shock resistance. This avoids distortion and risk of damage due to the localised pressures imposed by some alternative mechanical clamping methods.

Under normal circumstances, this section of the appliance should require no in-field service and is sealed against dust ingress.

Periodic inspection of the bonded joints between the flip enclosure and the front and rear tube sections is recommended. If disturbance to these joints is observed, the device should not be used and the manufacturer should be consulted.

The Letus35 does not have any provision for fastening to third party accessories. However supporting the Letus35/camcorder combination on a rods based structure is recommended.

Fixing of the Letus35 to other structures such as rods based support systems has been reported as achievable by use of a shaped base to match either the front tube or flip enclosure, support strap or a firm base under the flip enclosure and retention by strapping across the appliance to the same base loading point.

If mounting the appliance to a third party rods-filterbox-lens hood assembly, take care that precise spacing or packing is installed between the camcorder base and the baseplate mount and between the Letus35 body and base fitting chosen. All contact surfaces must be parallel prior to fastening or abnormal stresses will be imposed.

If accurate packing is not fitted and the Letus35 body is cinched down hard with a strap, optical alignment may be compromised and damage may also be done to the Letus35 and the camcorder lens mount.

Important. The Letus35 flip for CanonXL/JVC body must not be permanently fixed down to a base support. The relay lens backfocus adjustment physically lengthens or shortens the entire appliance.

Attempts to adjust relay lens backfocus with the appliance in permanent fixture may cause bending of the appliance at the relay lens and possible damage to the camera at the mount.

DESCRIPTION:

The Letus35 works by causing the video camcorder to make a picture of a picture. The image is not directly "seen" by the camcorder.

P+S Technik support literature for their Mini35 and Pro35 products, uses the definition "non-coherent” to describe this process.

In general terms, this is the way film works. The Letus35 and other groundglass based image relay devices provide an instant relay of the image which can be immediately viewed.

Film based imaging requires time for processing, printing and extra hardware for exhibition.

THE PROCESS.

STAGE ONE.

The SLR lens image of the subject is projected upon a groundglass rear projection
screen. The texture of this screen is made invisible to the camcorder by rapid cyclic
motion of the screen on a plane 90 degrees to the optical centreline. The projected image however, remains unmoved, so the groundglass "grain" disappears.

Exposure levels to this screen have to be manually adjusted for best visual effect, brightness and sharpness by the SLR camera lens focus and aperture controls.

SLR lens aperture setting numbers between f3.5 and f1.8 or lower, provide best results. Lenses should preferably be chosen to provide f1.8 or better light gathering capability.

STAGE TWO.

The video camcorder makes an electronic recording of the image it sees on the
groundglass screen, ie., a picture of a picture.

The XL style camcorder, no longer has its own lens fitted when the Letus35 Flip for XL is installed and relies on the Letus35 relay lens to direct the images onto the sensor.

Furthurmore, all lens automatic functions are no longer there as is discovered with other manual lens adaptations to the XL style camcorder family. The brightness and sharpness of the groundglass image is furthur managed by the aperture and focus controls of the relay lens.

(A lens warning placard observed in the camcorder viewfinder is a normal circumstance when alternative non-servo lenses are used.)

SOME BEST PRACTICES:

Relay lens aperture setting is preferably kept in the area closest to f5.6. Sharpness of the groundglass image is achieved and maintained by the relay lens focus control.

When low lighting conditions do not permit the relay lens aperture to remain in the area of f5.6, very wide aperture settings may cause reduced sharpness of the image. More light is needed on the subject to enable the aperture to be closed to a setting suited for best performance

Narrower aperture settings than f3.5 on the SLR lens may introduce visible defects in the image sometimes referred to as “swirling” or “grain”. To remedy this problem, use SLR lens apertures wider open (lower numbers) than f3.5. Use of a fully wide aperture on some SLR lenses reduces sharpness performance of those lenses.

If the lighting of the subject remains too bright, reduce exposure by closing the relay aperture or adding a glass ND filter to the SLR lens or a piece of ND filter gel in the space behind the SLR lens in the lens mount. Outdoors shading in the form of diffusion screens might be needed.

Supplemental lighting or light reduction should not be regarded as a painful chore. Carefully composed lighting is in keeping with the quest for better production values videographers demonstrate by using an image relay device.

CONT'D BELOW.........

Bob Hart · June 30th, 2007, 09:01 AM

QUICK SETUP.
(More detailed instructions follow).

Carefully unpack then check the Letus35 for shipping damage. Make particular observation of the joints where the front and rear tubes fit up to the plastic flip enclosure.

If there is observable cracking, looseness or other disturbance to the joints, the manufacturer should be consulted before the device goes into service.

Dismount the standard lens from the camcorder. Take care to install the endcap to the lens to keep dust and moisture out while it is stored.

Mount the Letus35 to the XL style camcorder. It fits up like another lens.

Set relay aperture to f5.6 as a starting point.

Fit SLR lens to front mount of the Letus35.

Set SLR lens aperture to widest available as a starting point. (f1.8 on an f1.8 SLR lens).

Fit batteries and test run the GG motor. A faint hum may be audible. If it cannot be heard, the vibration might be felt by finger held against the front tube enclosure.

If doubt remains that the unit runs, the SLR lens may be removed and the groundglass screen observed through the front port behind the dust excluder glass panel. The movement of the groundglass is very small and barely observable.

Take care not to point the Letus35/camcorder combination at direct sunlight to assist this observation. Dangerous reflections from the glass dust excluder panel may cause permanent eye harm and disability. This practice may also damage the camcorder image sensor unless the camcorder has been disconnected from the Letus35.

Do not shine a strong torch into the optical path to assist observation unless the camcorder is no longer connected to the Letus35.

It is not important to test for motor operation at this point as operation can be observed through the camcorder viewfinder later as the next part of the normal operating procedure which is -.

Point the camcorder/Letus35 combination at something interesting and try it out - that simple.

Initial results may be disappointing as there are other adjustments yet to be made. Additionally, the operation of any groundglass based image relay device is a specific craft to be learned and practiced before consistent and predictable results can be expected.

MOUNTING THE LETUS35 TO THE CAMCORDER.

Ensure all surfaces are clean and dust free.

There is a red telltale dot on the relay lens, similar in appearance and position to the red telltale dot on the standard lens. It indicates the rotational position of the fitment.

As for the standard lens, the Letus35 tail-end should be offered up to the camcorder mount with the red telltale in the 12 O’clock position. The tail-end of the Letus35 is inserted into the mount until the flange faces butt, then rotated clockwise until the red telltale reaches the two o’clock position.

At this point, a click should be heard as the camcorder lens lock pin pops into position. During rotation, the Letus35, or any lens for that matter, should be supported to avoid undue wear on the mount. As with the standard lens and others, the appliance should be offered up to the camcorder square-on.

If the lens rotates past the position where the pin should lock in and the pin fails to pop out and lock in, the device should not go into service and the manufacturer should be consulted.

An undesirable practice by some operators of Canon XL style camcorders and other larger ENG style camcorders, is to offer up to the camcorder, the lens tail-end at a steep angle to find its way into the lens mount hole, before restoring the lens to its normal axis.

This method of mounting optics to the camcorder, sometimes referred to as "bottle opening" is definitely not recommended. It is most often attempted at night with the assistance of fingertips groping to find the mount. This is most definitely worst practice and risks introducing fingerbourne contaminants to the filter screen over the camera CCD block.

Do not under any circumstance, attempt to operate the camcorder with the genuine Canon factory lenses, or any alternative lens or device, with the red telltale dot at or close to the 12 o’clock position as the lens or device may fall off.

SUPPLEMENTAL NOTES.

Quyen Le generously shared information to other direct relay adaptor builders, that in very early development, the Letus35 tail-end made contact with conductive pins in the camcorder lens mount area.This was fatal to electronics of the test camcorder.

He cautioned other developers and builders to maintain safe clearances in this area. The current development maintains clearance between the pins and the metal tail of the Letus35.

However, if one of the pins should fail and become dislodged towards the tail of the Letus35, or some other non-standard lens all-metal adaptors or third party non-electrical lenses, contact might occur and cause failure of the camcorder.

As a hedge against this very unlikely event, it might be prudent to cut a narrow strip of thin adhesive tape and cover the pins themselves or that neighbouring section of all inserted all-metal adaptors and third party non-electrical lenses, whilst taking care not to cover over the window to the CCD or impede the mount.

Very good information on groundglass based image relay may be found as downloadable .pdf files at the P+S Technik website.

This company is the pioneer developer and eminent manufacturer of two groundglass based image relay systems which are very comprehensively integrated with film based motion picture production hardware and are regarded as an industry benchmark.

WARNING:

The author of these notes is neither an industry professional, nor approved by the manufacturer of the Letus35 systems to provide technical assistance.

The notes above are derived from personal experiments with the Letus35 XL flip model and may have adverse effects upon the Letus35 and camcorder which have not yet become manifest or observed.

Therefore, the decision by owners to attempt any adjustments to the Letus35 and consequences remain the owner's responsiblity alone.

Bob Hart · June 30th, 2007, 09:04 AM

SOME UNAUTHORISED NOTES RELATING TO LETUS35 INITIAL SETUP FOR NEW USERS.

FOREWORD:

New users may be disappointed by a smoky unclear image with visible blemishes when a bright uniform area like sky or a plain wall is shot.

Do not despair. In common with many groundglass based image relay devices, this is most often a worst case condition created by incorrect combinations of SLR lens/aperture settings and relay lens focus/aperture settings and in most instances can be corrected.

Letus35 users are warned that whilst following this instruction set may assist yield satisfactory results, there may be outcomes and damages to equipment which are unexpected.

This comment does not reflect any shortcoming or otherwise on the Letus35 systems or other groundglass based system but assumes possible incompetences of this author.

Readers of this instruction set are strongly advised to proactively confirm or refute these suggestions by independent reading, consultation with other persons and research :-

CHAPTER 1.

In-camera non-detachable lens system camcorder versions , eg PD150/FX1 styles.

Outdoors in clear sunlight looking at a whitebalance panel.

Do not switch Letus35 motor on yet.

Camcorder manual aperture f5.6. Use ND filter 1 or 2 if necessary.

Shutter 1/50th sec (PAL) 1/60th sec (NTSC).

Zoom in to frame GG completely.

Manual white balance.

SLR lens aperture set to f 11.

Autofocus on for 10 seconds, then select manual to lock off. - Groundglass texture should now be visible, appearance like light brown sandpaper.

SLR lens aperture reset for best brightness at aperture f5.6 or lower number.

Reset camcorder aperture and ND filters for best brightness. Try to stay close to f5.6 by using the ND filter.

Remove whitebalance panel and focus SLR lens on something. Some sandpaper texture may still be visible.

Turn on Letus35 motor. Sandpaper effect should disappear.

Added steps for advanced setup - SLR lens backfocus adjustment.

Mount camcorder/Letus35 on tripod.

Set up a focus target, Siemens pattern is ideal. Newspaper front page is adequate but not the best.

Measure 4ft or 1 metre from a point approximately 40mm rearwards from the front edge of the Letus35 tubular casework. (This position represents the SLR lens focal plane where the groundglass is located.) Position camera and target until this distance is correct.

Set SLR lens focus to its 1 metre or 4ft mark, whichever choice you have made. The image in the camcorder will not be clear.

Support SLR lens. Loosen thumbscrew on top of Letus35.

Gently turn the mount in the housing until the depth of field marks and the centre focusing mark on the lens barrel are on top or where you find them easiest to see.

Take care the lens itself does not move inside the mount and fall out. The dual purpose reversable Nikon/Canon mount does not have positive locking for the Nikon lenses. Some worn lenses or third party lenses may remain loose in the mount.

Gently slide the lens and the mount it is attached to, about 1mm forward in the front Letus35 housing. Take care not to draw the lens and mount too far foward as it may come out unexpectedly and cause you to drop it.

This will put you in the ballpark of having correct backfocus of the SLR lens. Move for fine adjustment from here.

It is helpful to have an assistant observing the camcorder viewfinder to report sharpness or a monitor display to look at if doing this alone.

While holding the lens and mount squarely in the best position, retighten the thumbscrew. The mount may tend to walk forward or backward as you tighten the screw. You may need to reset several times before the lens mount is set in the correct position.

Use the fine point of a dart or jewellers flat head screwdriver to scribe a mark around the lens mount where it enters the Letus35 front housing so you can quickly find the best position in the future if the mount is disturbed.

NOTE: If the mount is not squarely in the hole after backfocus is reset, then there may be an out-of-focus region in the image.

Why bother to set SLR lens backfocus?

For lenses 50mm or longer focal length, if you do not believe in best practices, it doesn't matter a lot.

However in buying the Letus35 you are aspiring to better production values. You may be using a focus puller and tape measure for setups. Then the reading off the lens barrel has to be spot on otherwise it is useless.

For wide and ultra-wide lenses 28mm or shorter focal lengths, these lenses may not work satisfactorily at all unless backfocus is correctly set and the mount is square in the housing.

CHAPTER 2.

For detachable lens camcorder styles - Canon XL/JVC HD100 or similar.

Outdoors in clear sunlight looking at a whitebalance panel.

Do not switch Letus35 motor on yet.

Relay lens (rear lens of LETUS35 assembly) manual aperture f5.6.

Shutter 1/50th sec (PAL) 1/60th sec (NTSC).

Manual white balance.

SLR lens aperture set to f11 or higher number until the image begins to darken.

Reset relay lens manual aperture to widest, f2.8 or lower number if avalable.

Manually focus the relay lens until the groundglass texture becomes visible and sharpest, appearance like light brown sandpaper.

(NOTE: The front of the LETUS35 housing will need to be supported by hand during this adjustment as frictional loadings on the relay lens focus mechanism will otherwise make the lens adjustment baulky and difficult.

Support of the LETUS35 Canon XL and JVC HD100 models on a rods or brace system is strongly recommended as the extra weight of the entire system and SLR lenses places added strain on the camcorder lens mounts. Must not be solidly fixed down as relay focus moves the body.)

Reset SLR lens aperture for best brightness at aperture f5.6 or lower number.

Reset relay lens aperture for best brightness.

(Try to stay close to f5.6 by using ND filter glass filters on the SLR lens or pieces of filter gel behind it in the space behind the lens mount and dust excluder glass on the LETUS35.

The available adjustments will mostly have sufficient range without need for added ND. When maximum SLR lens aperture is required for shallow depth of field effects, then added ND filters may be needed.

This is preferred to use of tighter compensating relay lens apertures like f16 or f22 which may provoke adverse diffractive effects.)

Remove whilebalance panel and focus SLR lens on something. Some sandpaper texture may still be visible.

Turn on Letus35 motor. Sandpaper effect should disappear.

Added steps for advanced setup - SLR lens backfocus adjustment.

Mount camcorder/Letus35 on tripod.

Set up a focus target, Siemens pattern is ideal. Newspaper front page is adequate but not the best.

Measure 4ft or 1 metre from a point approximately 40mm rearwards from the front edge of the Letus35 tubular casework. This represents the SLR lens focal plane where the groundglass is located. Position camera and target until this distance is correct.

Set SLR lens focus to its 1 metre or 4ft mark, whichever choice you have made. The image in the camcorder will not be clear.

Support SLR lens. Loosen thumbscrew on top of Letus35.

Gently turn the mount in the housing until the depth of field marks and the centre focussing mark on the lens barrel are on top or where you find them easiest to see.

Take care the lens itself does not move inside the mount and fall out. The dual purpose reversable Nikon/Canon mount does not have positive locking for the Nikon lenses. Some worn lenses or third party lenses may remain loose in the mount.

Gently slide the lens and the mount it is attached to about 1mm forward in the front Letus35 housing. Take care not to draw the lens and mount too far foward as it may come out unexpectedly and cause you to drop it.

This will put you in the ballpark of having correct backfocus of the SLR lens. Move for fine adjustment from here.

It is helpful to have an assistant observing the camcorder viewfinder to report sharpness or a monitor display to look at if doing this alone.

While holding the lens and mount squarely in the best position, retighten the thumbscrew. The mount may tend to walk forward or backward as you tighten the screw. You may need to reset several times before the lens mount is set in the correct position.

Use the fine point of a dart or jewellers flat head screwdriver to scribe a mark around the lens mount where it enters the Letus35 front housing so you can quickly find the best position in the future if the mount is disturbed.

NOTE: If the mount is not squarely in the hole after backfocus is reset, then there may be an out-of-focus region in the image.

Why bother to set SLR lens backfocus?

For lenses 50mm or longer focal length, if you do not believe in best practices, it doesn't matter a lot.

However in buying the Letus35 you are aspiring to better production values. You may be using a focus puller and tape measure for setups. Then the reading off the lens barrel has to be spot on otherwise it is useless.

For wide and ultra-wide lenses 28mm or shorter focal lengths, these lenses may not work satisfactily at all unless backfocus is correctly set and the mount is square in the housing.

WARNING:

The author of these notes is neither an industry professional, nor approved by the manufacturer of the Letus35 systems to provide technical assistance.

The notes above are derived from personal experiments with the Letus35 XL and HD100 flip models and may have adverse effects upon the Letus35 and camcorder which have not yet become manifest or observed.

Therefore, the decision by owners to attempt any adjustments to the Letus35 and consequences remain the owner's responsiblity alone.

Bob Hart · June 30th, 2007, 09:17 AM

I have not used Quyen's Letus35 extensively so my comments have no quality for the Letus35.

I have made my own device and have some observations about it.

If you mix Letus and non-Letus images, you may find a difference in sharpness and contrast.

You may find that for detail sharpness in your wide-angle shots, using no Letus35 may give you clearer images.

In wide-angle images, you generally seek a lot more background detail in sharper focus.

Your camcorder also may give you a much wider field of view than any standard movie frame 35mm adaptor can unless you use some seriously expensive 35mm lenses.

My personal preference would be to shoot direct-to-camera for wide shots, streetscapes, landscapes etc., where a lot of detail is wanted.

Use the Letus35 for the closer work like interviews or the shots where you want to exploit that narrow DOF effect. You can reduce contrast and sharpness in post-production but you cannot realistically put back what is not there in a image.

I would avoid sun-across, extremely high-contrast, or into-sun situations. These may aggravate any tendency towards grain showing when you play with apertures for best lighting of your subject.

Against the light with a good bounce lighting onto your subject from a reflector or added artificial lighting, the image can still look good, so there are always exceptions.

From a technical standpoint, my own device is not as pure a follower of the Mini35 process as others.

To assist integration with non-relay footage, I have customised my groundglass a little with slight backpolishing for a little of the aerial image to come through. This gives more of a video look, confers a little more sharpness and yields less light loss.

The downside is some lighting situations have to be avoided to prevent a halo/ghosting effect on strongly lit out-of-focus objects in the image.

This is why my comments are unqualified relating to the Letus35.

I would not recommend you fit the Letus35 then go straight out on the job.

With any relay device including the benchmark P+S Technik Mini35, it is a craft to be learned with much practice or lost work and frustration are sure to be companions.

As is normal when using any new appliance or film stock, I would go out and shoot extensive tests and aquire the reflexes with the camera-Letus35 combination that you need for your best intuitive and reactive work.

Bob Hart · June 30th, 2007, 09:59 AM

Below are some links to YouTube clips relating to the Letus35 product family. In the clip descriptions click on the ''more" highlight to expand the description as additional information is added from time to time.

LETUS35 MODIFIED - http://www.youtube.com/watch?v=-O-Dl7oZTZs

LETUS35 DISMANTLED - http://www.youtube.com/watch?v=yugfv4ZVXgg

Below are links to the savefile site to .jpg images.

Two illustrate a method of securing Nikon lenses from unwanted movement in a reversable Canon/Nikon mount which may be found on a Letus35.

Two illustrate one method of supporting the Letus35 flip body on a 12.5mm rods system, in this example, a generic teleprompter mount. The optical centres are not correct for matte-box mounting.

A product from Cavision exists to support the Letus35 flip body without constraining its lengthening or shortening during backfocus movements.

These cannot be viewed on-site but must be downloaded from the site, which some web users regard as risky practice.

http://www.savefile.com/files/836553

http://www.savefile.com/files/836576

http://www.savefile.com/files/836584

http://www.savefile.com/files/836596

The savefile postings have an end-date which extends only if the files are periodically accessed. If any of these links yield an expired placard, please let me know by dvinfo email and I will restore them.

In meantime, if anyone is able to teach me how to make these .jpg files directly uploadable to dvinfo without resolution loss for expanded viewing, this would be appreciated.

Below is a link to a very useful focus chart. In absence of a larger monitor, several of these printed charts, held up at precise focus points and removed immediately prior to the take can assist accurate focus and focus pulls in otherwise non-dynamic setups.

http://www.rondexter.com/focus_pattern.pdf

Bob Hart · September 25th, 2007, 10:28 PM

FOOTNOTE TO THE SAVEFILE LINKS ABOVE

When you are linked into Savefile, you need to get down to the lower right of the page and click on the download button pretty quicksmart before you get jumped by a fuillscreen banner ad.

If the file does not begin to download, there is a prompt which tells you to click on it and this works fine.

The four images are large .jpg files and take a minute or so to come down.

Bob Hart · June 22nd, 2008, 05:49 PM

All of the savefile.com images linked to in the preceding post have now timed out due to inactivity. Given that Letus Corp has long ago revised their Nikon mounts which are available for purchase, there is little point to reposting the fix.

June 30th, 2007, 08:52 AM	#1
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	A Clayton's Sticky - Letus35 Flip For Xl My original posts have sunk fairly deep by now into the chasms of post past. Here following below are re-posts of some which have also been updated to reflect more recent experiences. Please do not blindly read and follow the practices described as I am neither the inventor of the Letus35, nor a continous user of the appliance. There may be unintended consequences of injury to the operator of the Letus35/Camera combination and damage to the appliance and attached camera. Owners of the Letus35/camera combination can and are advised to choose not to apply any of the methods and practices described in the following posts, but to conduct their own researches into the appliances and their proper and safe use. The consequences of any adjustments or use of the methods decribed by me therefore remain the responsibility of the owner/operator alone. These notes are published in hope of being some assistance to new owners until such time as the manufacturer is able to publish a handbook. Last edited by Bob Hart; June 30th, 2007 at 08:53 AM. Reason: error

June 30th, 2007, 08:55 AM	#2
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Non-authorised Operator Instructions. NON-AUTHORISED OPERATOR INSTRUCTIONS. LETUS35 FLIP MOTION PICTURE FILM EMULATOR FOR THE CANON XL FAMILY OF CAMCORDERS. FOREWORD: Letus35 users are warned that whilst following this instruction set may assist yield satisfactory results, there may be outcomes and damages to equipment which are unexpected. This comment does not reflect any shortcoming or otherwise on the Letus35 systems or other groundglass based image relay systems but assumes possible incompetences of this author. Readers of this instruction set are strongly advised to proactively confirm or refute these suggestions by independent reading, consultation with other persons and research :- INTRODUCTION. The Letus35 Flip is an erecting non-coherent image relay device which enables popular full frame capable Nikon F Mount and Canon Mount 35mm camera lenses to be fitted to the camcorder, yet achieve nearer to the same fields of view available to the still photographer or motion picture film camera operator. The 35mm motion picture image frame is the most closely emulated. This facility enables the camcorder operator to replicate the available narrow depth of field and perspective effects normally associated with the larger available imaging area of 35mm film for a given lens focal length. In addition, the indirect relay of the image via a groundglass screen confers an image aesthetic more in common with motion picture film images. A feature of the LETUS35 family of adaptors is the unique groundglass motion system. The design confers self-counterbalancing of the entire moving structure. Two stages of rubber support coupling isolate the moving structure from the casework. Any vibration is caused only by passive structural resistance to the motion by the necessary support of the moving structure and not by direct imposition of torque or mass-reaction loads. HANDLING. The Letus35, should be treated with the due care normal for optical instruments. Avoid sharp impacts, extremes of temperature, especially rapid changes, dust and rainfall. The Letus35 should ideally be transported in its own padded case in a supporting profile in the manner of other optical products and cameras. Unless in actual use in a mobile environment, transport of the assembled camcorder/Letus35 combination, as for the normal camcorder/genuine Canon lenses combination, is not recommended. The lens mount may be subjected to abnormal stress in this circumstance. The “flip” or erecting component of the optical path consists of surface coated mirrors, chosen for least light loss and less weight. They are mounted in a stout, precisely machined, plastic case. The mirrors are fixed into the flip enclosure with non-hardening silicon adhesive which provides firm mounting with some shock resistance. This avoids distortion and risk of damage due to the localised pressures imposed by some alternative mechanical clamping methods. Under normal circumstances, this section of the appliance should require no in-field service and is sealed against dust ingress. Periodic inspection of the bonded joints between the flip enclosure and the front and rear tube sections is recommended. If disturbance to these joints is observed, the device should not be used and the manufacturer should be consulted. The Letus35 does not have any provision for fastening to third party accessories. However supporting the Letus35/camcorder combination on a rods based structure is recommended. Fixing of the Letus35 to other structures such as rods based support systems has been reported as achievable by use of a shaped base to match either the front tube or flip enclosure, support strap or a firm base under the flip enclosure and retention by strapping across the appliance to the same base loading point. If mounting the appliance to a third party rods-filterbox-lens hood assembly, take care that precise spacing or packing is installed between the camcorder base and the baseplate mount and between the Letus35 body and base fitting chosen. All contact surfaces must be parallel prior to fastening or abnormal stresses will be imposed. If accurate packing is not fitted and the Letus35 body is cinched down hard with a strap, optical alignment may be compromised and damage may also be done to the Letus35 and the camcorder lens mount. Important. The Letus35 flip for CanonXL/JVC body must not be permanently fixed down to a base support. The relay lens backfocus adjustment physically lengthens or shortens the entire appliance. Attempts to adjust relay lens backfocus with the appliance in permanent fixture may cause bending of the appliance at the relay lens and possible damage to the camera at the mount. DESCRIPTION: The Letus35 works by causing the video camcorder to make a picture of a picture. The image is not directly "seen" by the camcorder. P+S Technik support literature for their Mini35 and Pro35 products, uses the definition "non-coherent” to describe this process. In general terms, this is the way film works. The Letus35 and other groundglass based image relay devices provide an instant relay of the image which can be immediately viewed. Film based imaging requires time for processing, printing and extra hardware for exhibition. THE PROCESS. STAGE ONE. The SLR lens image of the subject is projected upon a groundglass rear projection screen. The texture of this screen is made invisible to the camcorder by rapid cyclic motion of the screen on a plane 90 degrees to the optical centreline. The projected image however, remains unmoved, so the groundglass "grain" disappears. Exposure levels to this screen have to be manually adjusted for best visual effect, brightness and sharpness by the SLR camera lens focus and aperture controls. SLR lens aperture setting numbers between f3.5 and f1.8 or lower, provide best results. Lenses should preferably be chosen to provide f1.8 or better light gathering capability. STAGE TWO. The video camcorder makes an electronic recording of the image it sees on the groundglass screen, ie., a picture of a picture. The XL style camcorder, no longer has its own lens fitted when the Letus35 Flip for XL is installed and relies on the Letus35 relay lens to direct the images onto the sensor. Furthurmore, all lens automatic functions are no longer there as is discovered with other manual lens adaptations to the XL style camcorder family. The brightness and sharpness of the groundglass image is furthur managed by the aperture and focus controls of the relay lens. (A lens warning placard observed in the camcorder viewfinder is a normal circumstance when alternative non-servo lenses are used.) SOME BEST PRACTICES: Relay lens aperture setting is preferably kept in the area closest to f5.6. Sharpness of the groundglass image is achieved and maintained by the relay lens focus control. When low lighting conditions do not permit the relay lens aperture to remain in the area of f5.6, very wide aperture settings may cause reduced sharpness of the image. More light is needed on the subject to enable the aperture to be closed to a setting suited for best performance Narrower aperture settings than f3.5 on the SLR lens may introduce visible defects in the image sometimes referred to as “swirling” or “grain”. To remedy this problem, use SLR lens apertures wider open (lower numbers) than f3.5. Use of a fully wide aperture on some SLR lenses reduces sharpness performance of those lenses. If the lighting of the subject remains too bright, reduce exposure by closing the relay aperture or adding a glass ND filter to the SLR lens or a piece of ND filter gel in the space behind the SLR lens in the lens mount. Outdoors shading in the form of diffusion screens might be needed. Supplemental lighting or light reduction should not be regarded as a painful chore. Carefully composed lighting is in keeping with the quest for better production values videographers demonstrate by using an image relay device. CONT'D BELOW......... Last edited by Bob Hart; June 30th, 2007 at 09:26 AM. Reason: error

June 30th, 2007, 09:01 AM	#3
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Cont'd From Above........ QUICK SETUP. (More detailed instructions follow). Carefully unpack then check the Letus35 for shipping damage. Make particular observation of the joints where the front and rear tubes fit up to the plastic flip enclosure. If there is observable cracking, looseness or other disturbance to the joints, the manufacturer should be consulted before the device goes into service. Dismount the standard lens from the camcorder. Take care to install the endcap to the lens to keep dust and moisture out while it is stored. Mount the Letus35 to the XL style camcorder. It fits up like another lens. Set relay aperture to f5.6 as a starting point. Fit SLR lens to front mount of the Letus35. Set SLR lens aperture to widest available as a starting point. (f1.8 on an f1.8 SLR lens). Fit batteries and test run the GG motor. A faint hum may be audible. If it cannot be heard, the vibration might be felt by finger held against the front tube enclosure. If doubt remains that the unit runs, the SLR lens may be removed and the groundglass screen observed through the front port behind the dust excluder glass panel. The movement of the groundglass is very small and barely observable. Take care not to point the Letus35/camcorder combination at direct sunlight to assist this observation. Dangerous reflections from the glass dust excluder panel may cause permanent eye harm and disability. This practice may also damage the camcorder image sensor unless the camcorder has been disconnected from the Letus35. Do not shine a strong torch into the optical path to assist observation unless the camcorder is no longer connected to the Letus35. It is not important to test for motor operation at this point as operation can be observed through the camcorder viewfinder later as the next part of the normal operating procedure which is -. Point the camcorder/Letus35 combination at something interesting and try it out - that simple. Initial results may be disappointing as there are other adjustments yet to be made. Additionally, the operation of any groundglass based image relay device is a specific craft to be learned and practiced before consistent and predictable results can be expected. MOUNTING THE LETUS35 TO THE CAMCORDER. Ensure all surfaces are clean and dust free. There is a red telltale dot on the relay lens, similar in appearance and position to the red telltale dot on the standard lens. It indicates the rotational position of the fitment. As for the standard lens, the Letus35 tail-end should be offered up to the camcorder mount with the red telltale in the 12 O’clock position. The tail-end of the Letus35 is inserted into the mount until the flange faces butt, then rotated clockwise until the red telltale reaches the two o’clock position. At this point, a click should be heard as the camcorder lens lock pin pops into position. During rotation, the Letus35, or any lens for that matter, should be supported to avoid undue wear on the mount. As with the standard lens and others, the appliance should be offered up to the camcorder square-on. If the lens rotates past the position where the pin should lock in and the pin fails to pop out and lock in, the device should not go into service and the manufacturer should be consulted. An undesirable practice by some operators of Canon XL style camcorders and other larger ENG style camcorders, is to offer up to the camcorder, the lens tail-end at a steep angle to find its way into the lens mount hole, before restoring the lens to its normal axis. This method of mounting optics to the camcorder, sometimes referred to as "bottle opening" is definitely not recommended. It is most often attempted at night with the assistance of fingertips groping to find the mount. This is most definitely worst practice and risks introducing fingerbourne contaminants to the filter screen over the camera CCD block. Do not under any circumstance, attempt to operate the camcorder with the genuine Canon factory lenses, or any alternative lens or device, with the red telltale dot at or close to the 12 o’clock position as the lens or device may fall off. SUPPLEMENTAL NOTES. Quyen Le generously shared information to other direct relay adaptor builders, that in very early development, the Letus35 tail-end made contact with conductive pins in the camcorder lens mount area.This was fatal to electronics of the test camcorder. He cautioned other developers and builders to maintain safe clearances in this area. The current development maintains clearance between the pins and the metal tail of the Letus35. However, if one of the pins should fail and become dislodged towards the tail of the Letus35, or some other non-standard lens all-metal adaptors or third party non-electrical lenses, contact might occur and cause failure of the camcorder. As a hedge against this very unlikely event, it might be prudent to cut a narrow strip of thin adhesive tape and cover the pins themselves or that neighbouring section of all inserted all-metal adaptors and third party non-electrical lenses, whilst taking care not to cover over the window to the CCD or impede the mount. Very good information on groundglass based image relay may be found as downloadable .pdf files at the P+S Technik website. This company is the pioneer developer and eminent manufacturer of two groundglass based image relay systems which are very comprehensively integrated with film based motion picture production hardware and are regarded as an industry benchmark. WARNING: The author of these notes is neither an industry professional, nor approved by the manufacturer of the Letus35 systems to provide technical assistance. The notes above are derived from personal experiments with the Letus35 XL flip model and may have adverse effects upon the Letus35 and camcorder which have not yet become manifest or observed. Therefore, the decision by owners to attempt any adjustments to the Letus35 and consequences remain the owner's responsiblity alone.

June 30th, 2007, 09:04 AM	#4
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Non-authorised Initial Setup Instructions SOME UNAUTHORISED NOTES RELATING TO LETUS35 INITIAL SETUP FOR NEW USERS. FOREWORD: New users may be disappointed by a smoky unclear image with visible blemishes when a bright uniform area like sky or a plain wall is shot. Do not despair. In common with many groundglass based image relay devices, this is most often a worst case condition created by incorrect combinations of SLR lens/aperture settings and relay lens focus/aperture settings and in most instances can be corrected. Letus35 users are warned that whilst following this instruction set may assist yield satisfactory results, there may be outcomes and damages to equipment which are unexpected. This comment does not reflect any shortcoming or otherwise on the Letus35 systems or other groundglass based system but assumes possible incompetences of this author. Readers of this instruction set are strongly advised to proactively confirm or refute these suggestions by independent reading, consultation with other persons and research :- CHAPTER 1. In-camera non-detachable lens system camcorder versions , eg PD150/FX1 styles. Outdoors in clear sunlight looking at a whitebalance panel. Do not switch Letus35 motor on yet. Camcorder manual aperture f5.6. Use ND filter 1 or 2 if necessary. Shutter 1/50th sec (PAL) 1/60th sec (NTSC). Zoom in to frame GG completely. Manual white balance. SLR lens aperture set to f 11. Autofocus on for 10 seconds, then select manual to lock off. - Groundglass texture should now be visible, appearance like light brown sandpaper. SLR lens aperture reset for best brightness at aperture f5.6 or lower number. Reset camcorder aperture and ND filters for best brightness. Try to stay close to f5.6 by using the ND filter. Remove whitebalance panel and focus SLR lens on something. Some sandpaper texture may still be visible. Turn on Letus35 motor. Sandpaper effect should disappear. Added steps for advanced setup - SLR lens backfocus adjustment. Mount camcorder/Letus35 on tripod. Set up a focus target, Siemens pattern is ideal. Newspaper front page is adequate but not the best. Measure 4ft or 1 metre from a point approximately 40mm rearwards from the front edge of the Letus35 tubular casework. (This position represents the SLR lens focal plane where the groundglass is located.) Position camera and target until this distance is correct. Set SLR lens focus to its 1 metre or 4ft mark, whichever choice you have made. The image in the camcorder will not be clear. Support SLR lens. Loosen thumbscrew on top of Letus35. Gently turn the mount in the housing until the depth of field marks and the centre focusing mark on the lens barrel are on top or where you find them easiest to see. Take care the lens itself does not move inside the mount and fall out. The dual purpose reversable Nikon/Canon mount does not have positive locking for the Nikon lenses. Some worn lenses or third party lenses may remain loose in the mount. Gently slide the lens and the mount it is attached to, about 1mm forward in the front Letus35 housing. Take care not to draw the lens and mount too far foward as it may come out unexpectedly and cause you to drop it. This will put you in the ballpark of having correct backfocus of the SLR lens. Move for fine adjustment from here. It is helpful to have an assistant observing the camcorder viewfinder to report sharpness or a monitor display to look at if doing this alone. While holding the lens and mount squarely in the best position, retighten the thumbscrew. The mount may tend to walk forward or backward as you tighten the screw. You may need to reset several times before the lens mount is set in the correct position. Use the fine point of a dart or jewellers flat head screwdriver to scribe a mark around the lens mount where it enters the Letus35 front housing so you can quickly find the best position in the future if the mount is disturbed. NOTE: If the mount is not squarely in the hole after backfocus is reset, then there may be an out-of-focus region in the image. Why bother to set SLR lens backfocus? For lenses 50mm or longer focal length, if you do not believe in best practices, it doesn't matter a lot. However in buying the Letus35 you are aspiring to better production values. You may be using a focus puller and tape measure for setups. Then the reading off the lens barrel has to be spot on otherwise it is useless. For wide and ultra-wide lenses 28mm or shorter focal lengths, these lenses may not work satisfactorily at all unless backfocus is correctly set and the mount is square in the housing. CHAPTER 2. For detachable lens camcorder styles - Canon XL/JVC HD100 or similar. Outdoors in clear sunlight looking at a whitebalance panel. Do not switch Letus35 motor on yet. Relay lens (rear lens of LETUS35 assembly) manual aperture f5.6. Shutter 1/50th sec (PAL) 1/60th sec (NTSC). Manual white balance. SLR lens aperture set to f11 or higher number until the image begins to darken. Reset relay lens manual aperture to widest, f2.8 or lower number if avalable. Manually focus the relay lens until the groundglass texture becomes visible and sharpest, appearance like light brown sandpaper. (NOTE: The front of the LETUS35 housing will need to be supported by hand during this adjustment as frictional loadings on the relay lens focus mechanism will otherwise make the lens adjustment baulky and difficult. Support of the LETUS35 Canon XL and JVC HD100 models on a rods or brace system is strongly recommended as the extra weight of the entire system and SLR lenses places added strain on the camcorder lens mounts. Must not be solidly fixed down as relay focus moves the body.) Reset SLR lens aperture for best brightness at aperture f5.6 or lower number. Reset relay lens aperture for best brightness. (Try to stay close to f5.6 by using ND filter glass filters on the SLR lens or pieces of filter gel behind it in the space behind the lens mount and dust excluder glass on the LETUS35. The available adjustments will mostly have sufficient range without need for added ND. When maximum SLR lens aperture is required for shallow depth of field effects, then added ND filters may be needed. This is preferred to use of tighter compensating relay lens apertures like f16 or f22 which may provoke adverse diffractive effects.) Remove whilebalance panel and focus SLR lens on something. Some sandpaper texture may still be visible. Turn on Letus35 motor. Sandpaper effect should disappear. Added steps for advanced setup - SLR lens backfocus adjustment. Mount camcorder/Letus35 on tripod. Set up a focus target, Siemens pattern is ideal. Newspaper front page is adequate but not the best. Measure 4ft or 1 metre from a point approximately 40mm rearwards from the front edge of the Letus35 tubular casework. This represents the SLR lens focal plane where the groundglass is located. Position camera and target until this distance is correct. Set SLR lens focus to its 1 metre or 4ft mark, whichever choice you have made. The image in the camcorder will not be clear. Support SLR lens. Loosen thumbscrew on top of Letus35. Gently turn the mount in the housing until the depth of field marks and the centre focussing mark on the lens barrel are on top or where you find them easiest to see. Take care the lens itself does not move inside the mount and fall out. The dual purpose reversable Nikon/Canon mount does not have positive locking for the Nikon lenses. Some worn lenses or third party lenses may remain loose in the mount. Gently slide the lens and the mount it is attached to about 1mm forward in the front Letus35 housing. Take care not to draw the lens and mount too far foward as it may come out unexpectedly and cause you to drop it. This will put you in the ballpark of having correct backfocus of the SLR lens. Move for fine adjustment from here. It is helpful to have an assistant observing the camcorder viewfinder to report sharpness or a monitor display to look at if doing this alone. While holding the lens and mount squarely in the best position, retighten the thumbscrew. The mount may tend to walk forward or backward as you tighten the screw. You may need to reset several times before the lens mount is set in the correct position. Use the fine point of a dart or jewellers flat head screwdriver to scribe a mark around the lens mount where it enters the Letus35 front housing so you can quickly find the best position in the future if the mount is disturbed. NOTE: If the mount is not squarely in the hole after backfocus is reset, then there may be an out-of-focus region in the image. Why bother to set SLR lens backfocus? For lenses 50mm or longer focal length, if you do not believe in best practices, it doesn't matter a lot. However in buying the Letus35 you are aspiring to better production values. You may be using a focus puller and tape measure for setups. Then the reading off the lens barrel has to be spot on otherwise it is useless. For wide and ultra-wide lenses 28mm or shorter focal lengths, these lenses may not work satisfactily at all unless backfocus is correctly set and the mount is square in the housing. WARNING: The author of these notes is neither an industry professional, nor approved by the manufacturer of the Letus35 systems to provide technical assistance. The notes above are derived from personal experiments with the Letus35 XL and HD100 flip models and may have adverse effects upon the Letus35 and camcorder which have not yet become manifest or observed. Therefore, the decision by owners to attempt any adjustments to the Letus35 and consequences remain the owner's responsiblity alone.

June 30th, 2007, 09:17 AM	#5
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Some Generic Handling Notes I have not used Quyen's Letus35 extensively so my comments have no quality for the Letus35. I have made my own device and have some observations about it. If you mix Letus and non-Letus images, you may find a difference in sharpness and contrast. You may find that for detail sharpness in your wide-angle shots, using no Letus35 may give you clearer images. In wide-angle images, you generally seek a lot more background detail in sharper focus. Your camcorder also may give you a much wider field of view than any standard movie frame 35mm adaptor can unless you use some seriously expensive 35mm lenses. My personal preference would be to shoot direct-to-camera for wide shots, streetscapes, landscapes etc., where a lot of detail is wanted. Use the Letus35 for the closer work like interviews or the shots where you want to exploit that narrow DOF effect. You can reduce contrast and sharpness in post-production but you cannot realistically put back what is not there in a image. I would avoid sun-across, extremely high-contrast, or into-sun situations. These may aggravate any tendency towards grain showing when you play with apertures for best lighting of your subject. Against the light with a good bounce lighting onto your subject from a reflector or added artificial lighting, the image can still look good, so there are always exceptions. From a technical standpoint, my own device is not as pure a follower of the Mini35 process as others. To assist integration with non-relay footage, I have customised my groundglass a little with slight backpolishing for a little of the aerial image to come through. This gives more of a video look, confers a little more sharpness and yields less light loss. The downside is some lighting situations have to be avoided to prevent a halo/ghosting effect on strongly lit out-of-focus objects in the image. This is why my comments are unqualified relating to the Letus35. I would not recommend you fit the Letus35 then go straight out on the job. With any relay device including the benchmark P+S Technik Mini35, it is a craft to be learned with much practice or lost work and frustration are sure to be companions. As is normal when using any new appliance or film stock, I would go out and shoot extensive tests and aquire the reflexes with the camera-Letus35 combination that you need for your best intuitive and reactive work. Last edited by Bob Hart; June 30th, 2007 at 09:18 AM. Reason: error

June 30th, 2007, 09:59 AM	#6
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Some A/v Resource Material For Letus35 Below are some links to YouTube clips relating to the Letus35 product family. In the clip descriptions click on the ''more" highlight to expand the description as additional information is added from time to time. LETUS35 MODIFIED - http://www.youtube.com/watch?v=-O-Dl7oZTZs LETUS35 DISMANTLED - http://www.youtube.com/watch?v=yugfv4ZVXgg Below are links to the savefile site to .jpg images. Two illustrate a method of securing Nikon lenses from unwanted movement in a reversable Canon/Nikon mount which may be found on a Letus35. Two illustrate one method of supporting the Letus35 flip body on a 12.5mm rods system, in this example, a generic teleprompter mount. The optical centres are not correct for matte-box mounting. A product from Cavision exists to support the Letus35 flip body without constraining its lengthening or shortening during backfocus movements. These cannot be viewed on-site but must be downloaded from the site, which some web users regard as risky practice. http://www.savefile.com/files/836553 http://www.savefile.com/files/836576 http://www.savefile.com/files/836584 http://www.savefile.com/files/836596 The savefile postings have an end-date which extends only if the files are periodically accessed. If any of these links yield an expired placard, please let me know by dvinfo email and I will restore them. In meantime, if anyone is able to teach me how to make these .jpg files directly uploadable to dvinfo without resolution loss for expanded viewing, this would be appreciated. Below is a link to a very useful focus chart. In absence of a larger monitor, several of these printed charts, held up at precise focus points and removed immediately prior to the take can assist accurate focus and focus pulls in otherwise non-dynamic setups. http://www.rondexter.com/focus_pattern.pdf Last edited by Bob Hart; June 30th, 2007 at 10:38 AM. Reason: added information

September 25th, 2007, 10:28 PM	#7
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	FOOTNOTE TO THE SAVEFILE LINKS ABOVE When you are linked into Savefile, you need to get down to the lower right of the page and click on the download button pretty quicksmart before you get jumped by a fuillscreen banner ad. If the file does not begin to download, there is a prompt which tells you to click on it and this works fine. The four images are large .jpg files and take a minute or so to come down.

June 22nd, 2008, 05:49 PM	#8
Bob Hart Inner Circle Join Date: Dec 2003 Location: PERTH. W.A. AUSTRALIA. Posts: 4,476	Footnote All of the savefile.com images linked to in the preceding post have now timed out due to inactivity. Given that Letus Corp has long ago revised their Nikon mounts which are available for purchase, there is little point to reposting the fix.