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Old September 17th, 2006, 05:52 PM   #1
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Just tested my new Letus35A

I recently purchased a Letus35A, and thought I'd post my findings. I hope these are helpful for people planning similar equipment acquisitions.

Upfront: praise and kudos to Quyen. It's tough being a small business owner, and I know he routinely works into the middle of the night to bring us these innovative and economically-priced solutions.

Oh, and I am not a professional, not at all. I've only just completed one class for my film and TV course, and the quality of the material you see here reflects that. My ambitions for this equipment project were:

1. Add film-look depth of focus to my hand-held shots
2. Keep to a very low budget (under $750 for the Letus, 4 lenses, rails etc.)

So... I bought the standard model (not the flip) but I did order the $400 longer custom version for the Sony HVR-A1U and the HDR-HC1. I bought a Canon FL 28mm f3.5, a 35mm f2.5, a 50mm f1.4 and a 85mm f1.8 on eBay to test this unit with.

Quyen's devices are quite ingenious and certainly seem to be good value vis-à-vis the competition (although I don't own any of them, so cannot make any real comparisons, just going on cost and published features). I'd like to see the 58mm back connector 'set-up' improved a little, I think with time the single screw that hold the Achromat in place might wear, especially if you run around with the camera a lot, as I intend to do. Otherwise I have no real complaints.

Despite all the talk about framing and focus, I honestly have not found it that hard to get reasonable results. It's tricky for sure, and I expect I would invest in a good LCD like the Marshall, if I was going to do a lot of work with this. I used the viewfinder on my Sony and found by keeping the expanded focus button depressed, quickly checking the back-focus, hitting record and then jumping to the Canon lens, I was able to get reasonably good results (not something I'd want to trust a $$$ production, or a rapidly moving un-missable event to of course).

I found myself using a stack (+5) of diopters to minimize the amount of zooming I had to do. Lens-wise I found that there was some circular image fall off with all the lenses under 85mm (with the minimum of zooming, taking me just inside the border of the GG). The 85mm worked very well though.

I found the grain, bokeh and contrast pretty much as others have reported. There is some softness in the image, and I found the camera's HDV codec often struggled with the fine color graduations in the out of focus areas. Again this is a problem inherent in the camera and the HDV compression algorithm, not a criticism of the Letus.

I think I would like to find a better Achromat/diopter combination that introduces some better quality glass and fewer elements into the 'mix' and I've asked Quyen for his advice on what to buy.

Vibration and noise in not an issue at all, in fact it is very easy to forget the vibrating unit is on.

I had hoped to use this set-up on top of a hand-held steadicam, so I could use it in street markets and other places where setting up a tripod isn't easy. I think it is going to take a lot of skill to get consistent reliable results (because of the slightly longer focal length of the 85mm lens I was using, and its tendency to emphasize movements).

The setup you see on the link below shows my Sony, the Letus and a Cokin P-series hood and filter holder held together with a modified Cavision 8mm rod set. I added longer carbon fibre rods myself, which I filled with Epoxy for greater strength. I added th Cavision belted support mid-way along the Letus (with a ring of foam padding) to give it some extra support and rigidity (thanks to Bernie at Cavision for his help here).

I already own the Cokin hood and a bunch of filters, so I thought I'd put them to good use. The whole things sits on top of a Varizoom Ultralite steadicam.

All in all I think this is a good product for the money. I think it lends itself more to carefully framed on-tripod work, preferably with a good flippable LCD, rather than as a practical tool for adding a better filmic look to my planned 'running and gunning'. No criticism of the product here, just what I am trying to achieve.

The clip you see at this link was captured in this way. I would note that this was my very first attempt at capturing anything with the Letus, so please excuse the abundant flaws in this short clip.

There is technical information about the clip, and what I did in FCP. The only thing I didn't mention there is obviously the 2.35 aspect ratio matte that I added.

I hope this is helpful and maybe interesting to some of you.

Here's the link:

http://web.mac.com/pramsbottom/iWeb/...us%20Test.html

Last edited by Paul Ramsbottom; September 17th, 2006 at 11:14 PM.
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Old September 18th, 2006, 09:25 AM   #2
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Hi,

Nice setup. The video seems soft and a bit on the bright side (i.e. Hazy) though. This is what I saw with a couple of the Letus35 setup in this forum. Not sure why as some other shots made by some people were really good. Not sure if it was Letus35 or 35A or the flipped version.
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Old September 19th, 2006, 12:30 AM   #3
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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 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 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. Now move it for fine adjustment.

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. Now move it for fine adjustment.

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.

Last edited by Bob Hart; September 19th, 2006 at 01:33 AM.
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Old September 19th, 2006, 12:50 AM   #4
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Deleted. Post doubled when time-out occurred during edit.
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Old September 19th, 2006, 02:07 AM   #5
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Thanks Bob

Thanks for that awesome primer, I have so much to learn. In fairness to Quyen, I am going to take my clip down until I have achieved some better results.
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Old September 19th, 2006, 09:11 AM   #6
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Here follows some furthur information extracted from the draft manual I was preparing. Being of a lazy nature I had decided to mind my own business, put it aside and not progress it furthur so there are a few errors and plot holes in the story. The following material is supplemental to the previous post above.

It should not be regarded as either an authoritive endorsement or critique of the Letus35 family of devices.

Furthurmore, my following discourse on the Letus35 and there existing no discourse by me regarding any other groundglass based image relay device, should not be interpreted by absence of such other discourse as inferred endorsement of the Letus35 device.

I have not had opportunity to test any other groundglass based image relay device except those of my own experimentation.

The manfacturers of the Letus35 device and the Canon XL family of camcorders have not been formally contacted and have not had the opportunity to repudiate or endorse any of the content of the following discourse.

This discourse has been posted in the interest of immediately assisting users who might un-necessarily return devices they have diifficulties with due to unknowing mismanagement of the LETUS35/camcorder combination.


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.


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 f5.6 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.)

CONTINUED IN FOLLOWING POST.

Last edited by Bob Hart; September 19th, 2006 at 09:55 AM.
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Old September 19th, 2006, 09:14 AM   #7
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CONTINUATION FROM PREVIOUS POST.

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 f5.6 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 f5.6. 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.



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 defnitely worst practice and risks introducing fingerbourne contaminants to the window over the 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, 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 section of all inserted all-metal adaptors, 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.
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Old October 12th, 2006, 05:01 PM   #8
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Link changed

Latest results using a new CO achromat are here: http://web.mac.com/pramsbottom/iWeb/...s%20Tests.html
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Old October 14th, 2006, 11:42 AM   #9
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What is the CO Achromat? is it part of the desin of the 35A or is it an add on?? I've been thinkin about buying one of these 35A's
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Old October 14th, 2006, 01:07 PM   #10
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It's a high quality achromat to use instead of the one which comes as standard with the Letus.

I have found that it produced some very good result but....

1. It is $220, more than half the cost of the Letus itself.
2. It's a little larger than the standard one, so you will need to modify the ring on the back of the Letus that holds it in place.

http://www.bhphotovideo.com/bnh/cont...ughType=search
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Old October 14th, 2006, 10:36 PM   #11
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I've cut my achromat out of the letus because my camera can easily focus on the GG without it. no vigneting. I think the image is so much better without it. am I missing something here? is it just because my DVC30 is able to focus on the GG without it and other camera aren't?
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Old October 14th, 2006, 10:57 PM   #12
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No, your DVC30 uses a 4:3 ccd footprint, and uses a relatively small lens. All of the Panasonic GS series of adapters can frame a full 24x36mm image at fairly close distances. This makes an achromat unneccessary, unless you're using very wide angle, slower lenses, or in some cases, cinema lenses.
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Old October 27th, 2006, 12:38 PM   #13
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can the z1 work with the letus without an achromat? I know the a1 can...what would be the advantage of this?

p.s. just posted in main forum a problem I am having with the Letus and zooms, a problem quyen is working on finding out why it is happening...
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Last edited by Phil Bloom; October 27th, 2006 at 05:37 PM.
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Old October 27th, 2006, 10:09 PM   #14
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Posts: 4,356
Phil

For the sake of a curiosity, while I had the XL Letus flip apart and the relay section and its optics removed, I offered it up to an FX1. A close-up lens was needed. 7+ was too strong (distance too short between cam and GG for close focus) 4+ was fine.

There was enough zoom range left at the high end to allow for small adjustments to composition and framing. I did this indoors with an old f1.2 55mm Nikon so it is not a valid test as such.

I don't know the non-flip model.

The achromatic doptres are both Century Optics and 58mm threaded. I mounted them to the camera with a 58mm - 72mm ring.
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