Matthew,

Do you have a picture of your setup? Congrats on getting so far so soon! I has taken me a good 6-7 months and I am nowhere near you as far as quality!

What are you using for a condenser and where did you purchase it? Are you still using the Macro lens - or did you get an achromat?

any questions about 35-dv homemade adapter
 

hi
first. english dont's my born language. excuseme
i'm making a 35mm-dv converter with static groundglass
i have a problem. on the GG apear a circle more lighting. do how can resolve it.
i think to use a old +4 filter used however condenser lens. it's ok?
* the cam lenses take focus on GG without close-up lenses. it's ok?
* the cam record the images inverted. do i rotate 180d after?
thank you

saludos

Yes Mathew! You have done an amazing job. I'm in the process of building a spinner, but yours takes the cake. Would you please let us know your design and what gg, condensor, etc. you used? I'm very impressed!

A bit of an update on the AGUS35 plumber's version.

After the Cunderdin Airshow debacle when the heat softened the glue and the appliance fell off the front of the camera like a melted candle, I finally got around to fitting another glass groundglass for two student single scene shoots.

I am also getting in some more prisms, this time with coatings on the reflective surfaces. In the meantime, I found I could just get the image through past the chips in the damaged prism if I positioned it the right way.

I had rejected this particular glass disk because it ran out and shook the camera too much and had forgotten it still existed.

This time, I took the time and trouble to remake the front lens mount cap and bring it closer to camera lens centreline and to set the backfocus sharp across the whole frame.

This is apparently very important for the wide angle lenses 28mm or similar. Whilst these have a greater depth of field than a zoom, it seems they are less tolerant of backfocus being off.

The results in bright daylight with the prime lenses are better. In poor light, there still is softness in the image. The glass gg does not flicker.

Despite being a f4 to f6.3 aperture, the Sigma 50 - 500mm zoom lens confers a satisfactory image via the groundglass in good lighting. The 2x doubler is a little softer. This lens must be supported otherwise it will pull the lens mount out of a plastic pipe cap.

Bob,
Thats great to hear you have a spinning glass adapter.

Could we possibly have some pictures? How was the disk created and centred?

I only read the first 50 pages of this thread so excuse me if this is a re post. I'm wondering about the setup they used for www.marlathemovie.com. It's a static ground glass setup. Well actually it's not even ground glass I believe it's a focusing screen of some kind for a slr. I assume you'd still get the 35mm dof with this setup. If you had a good enough screen grain probably wouldn't be a factor. No noise, no moving parts. alot smaller, and if built correctly you wouldn't have to mount the dv camera at a 90 degree angle to the slr body. If anyone is familiar with the adapter they used on that movie could you please explain why this adapter is undesirable. It seems to me that it should work perfectly, I must be missing something.

That is usually the factor!

Most peope following this type of design have had luck from the 'Nikon D' screens or the more expensive 'Beatie Screens'

Bob has had a spinning glass unit for a couple of years now, if I am not mistaken - it isn't anything new for him.

Rob,
I experimented heavily early on with using the Nikon D static screen. This setup is undesireable because as soon as you start closing the iris of the lens (no matter how fast it is) the grain becomes alarmingly apparent. If you have a 1.2 of 1.4 lens you would certainly want to close the aperture somewhat at certain times because the DOF will be almost too shallow. If you have a static setup, however, closing the iris instantly creates serious grain problems. I'm sure that if you talked to the creator(s) of Marla they'd confirm that they never closed the iris. If you want aperture control, you need to go either wax or moving gg, bottom line.

Also, having your $2,000+ camera mounted vertically into a 35mm SLR camera on a spraypainted wooden board is simply unprofessional and awkward. Who would want to steadicam that thing?

Finally, I encourage you to look at the stills of the movie on the site www.marlathemovie.com. Even when the aperture seems to be wide open, the "translucent waviness" characteristic of a static adapter is always there in areas of shots that are out of focus. To many of us (including lazy old me) that's simply unacceptable. Also it looks like they didn't flip the image the right way (the name tags and letters in the stills are backwards?) Anyway, look at the media on that website and ask yourself if you could really live with the results of that adapter. I should add that they had to go through each individual frame of that movie and manually remove the grain from each shot.

Well, with all that, it still looks great and is a very entertaining movie. The artifacts kinda contributed to the look and style of the movie.

Wayne.

My version is old news. The original glass disk was broken last March. With a number of distracting things going on I did not get around to making another. I experimented with split DVD+R disks and these looked promising but actually take as long as glass to dress in the machine I made to do it.

Glass disks with holes in them can be ordered from Ohara in Japan. That's the good bit. The bad bit is you have to figure and polish them yourself, then after you have a clear disk, then apply the 5 micron finish to one surface.

The other bad bit is you have to order about 10 of them to make it worthwhile for Ohara to do the job. They are otherwise courteous and turn the order around in good time. The disks are thin 1.3mm slices off a 5" approx optical glass round. After dressing they come down to 0.9mm.

It's not a task for the faint-hearted. I broke 6 getting the process right and also attempting to make wax composite disks. I broke another one because I did not see it attached to the dressing platen which had been stored away. Then the good one got broke at Cunderdin.

They arrive in Australia raw at approx $50 each which is also not for the faint-hearted.

I have one remaining raw disk and one remaining clear finished disk and one other gg which has to be repolished on the front face.

As for fixed groundglasses, they can be made to work well but have to be more closely managed for acceptable results, which is another piece of workload to get in the way of inspired creativity.

Even the combination of spinning groundglass erecting versions and permanent non-detachable lens style camcorders still challenges spontaneous camera work. - For the camera operator familiar with the camera type, the first instinct is to go for the camera's own lens controls, rather than the objective lens on front.

There are occasions when you forget to turn on the disk motor and the grain is not initially noticeable until a change of light occurs or you pan across a dark area. A moving groundglass takes away one layer of unpredictability. Using an erecting path takes away another and eliminates extra post work.

A bit of re-grading of colour and contrast in something like After-Effects or similar is all that is needed.

When you can handhold the device and walkabout with it, then it is of practical use.

If I can find somebody with fast broadband, I'll send a demo .avi DVD+R by post for upload. Unfortunately it is in PAL. I have also written a rough user guide but have not published as I don't want to get sued. Any volunteers to convert and upload the vision for me?

I've just been doing 2 small single scene shoots for the PAC Screen workshop and one more to go. I have been doing them all with the AGUS/PD150/Nikon combination. From a directorial viewpoint they are not good, but do demonstrate the desirability of using film fomat lenses.

Thanks guys. Spinning ground glass it is!

Wow Matthew's stuff ROCKS!! Would u be able to post the configuration?

1. SLR>PCX>GG>Camcorder ?
2. SLR>GG>PCX>x7Macro>Camcorder ?

Recommended GG thickness=0.9mm? (Optical Glass)
Recommened PCX size=24mmx18mm

Sean.

I can only speak for my own version of the appliance.

Optical path is :-

SLR Lens (Nikon Primes - 28mm 50mm 85mm, all f1.8) >> +46.5mm from lens mount flange face to rear face of glass disk which is the groundglass side, >> two right-angle prisms 40mm x 40mm x 52mm all 40mm common thickness, in 90 degree opposition (like binocular prisms) >> Century Optics 7+ Achromatic Dioptre, 58mm thread mount type >> PD150 camcorder.

There is no PCX or other condenser arrangement in my device as there is not enough space within to fit added optics. A lesser power dioptre would enable this but would result in a longer device.

The GG finish is 5 micron, with a slight backpolish with cerium oxide to get a trace of aerial image through for sharpness and less light loss. This comes at the cost of an image which is more like video than film and in certain lighting conditions, where there are strong overlit sharp edged highlights, there will be seen a fairly distinct shape surrounded by a halo effect. If normal lighting methods are used, the creative depth-of-field effects can be realised without artifacts most of the time.

This arrangement suits my need to be able to intercut AGUS origination with normal video.

HDV and the AGUS35

I managed to get my greasy hands upon a Sony HDV for long enough to examine if the 58mm filter mount Century Optics 7+ Achromatic Dioptre will work as a relay lens into this camera.

The good news is that it does with some limitations. The lens obviously is going to vignette in a cruel way on this camera. However, by the time you zoom in to frame a groundglass image about 24mm wide, the vignette has gone from the TV safe area at least. Zoom in appears to be about the same as for the PD150 in practical terms. The HDV camera has a zoom lens of shorter focal length, but the CCD set may be smaller also as the framing seems about the same for a similar setting.

The bad news is you have to make up an adaptor with 72mm filter thread on outside and 58mm filter thread on inside to mount this lens and the making of it is a bit awkward.

The Tamron lens I used as a pattern for the 72mm filter mount has a different flavour of 72mm diameter. The plastic Sony case with its molded thread was a bit snug by about 0.2mm for a smooth fit on the Tamron.

It seems on my enquiries so far that there is no 72mm filter mount 7+ Achromatic dioptre available from anybody yet.

The appliance was offered up to the front of the camera by hand after the lens was mounted. The image seemed sharp across the width of the TV safe area viewable in the LCD. I did not have access to an underscanning HD monitor.

After I have made up the rear mount to the pattern I have taken from the camera, I'll see if I can get hold of it again and do some tests. This camera was the Sony HDR-FX1E. I understand there is a semi-professional camera based on this one.

If anyone has the computer hardware which can digest HDV for PAL and is willing to offer to capture the tape to HDV standard, I will send the test tape to a postal address.

Regards and all the best for the Christmas just past and for the coming New Year.

For HD via Sony's HDR-FX1E via the AGUS35 principle, certainly with the CD-R sized spinner versions, there appear likely two issues.


Steadyness of the image. -

Apparently HD broadcast compression cannot continuously deal with change of the whole image from one frame to the next frame, only partial changes in the image. (I have already observed the artifact of the far wall of a valley, framed by edges of a roadside forest, staying put when the camera view moves very slightly.)

There has been mention of certain Super16 capable film cameras being unsuitable because of lateral weave due to no positive pressure applied to the film edge in the gate.

AGUS versions using the CD sized disk seem to be prone to a little flicker in the image from plastic disks or slight shiver of movement of the whole image due to run-out of these disks or the glass disks I have so far attempted to make.


Resolution limits.

A 24mm x 18mm movie frame appears to require too much magnification to permit HD quality detail from my combination of 5 micron AO finished glass disk prisms and dioptre. My erecting version does not permit a larger frame to be used due to the prism size (28mm width limit).

Subjectively, the resolution seems to fall somewhere between SD and HD. Some of this might be in the prism/dioptre/camcorder lens combination, as it seems difficult to get a really sharp focus on the grain of the stationary groundglass. It rests within the focal range of the lens.


Another issue appears with the widescreen (16:9) view. The camera zoom hits its limit just on the point where the edges of the farmost prism move outside the frame in the viewfinder which means they will be there in underscan.

The 40mm x 40mm x 56mm prism pair only supports an image width of 28mm at best (ie., half of 56mm). They require about 120mm distance in the image path disk-to-lens by the time you make up mounts etc.. and the front prism is within 8mm of the disk, the apex of the rear within 3mm of the rim of the dioptre lens on the camcorder.

You could get a shorter path by glueing the prisms together and clamping them from the sides, but then the construction gets really complex.

Bigger prisms to allow a bigger image frame on the groundglass (assuming you can fit in a condenser as well to deal with the hotspot) require a longer path which means a lower power dioptre which means a furthur zoom-in which is not available on the HDR-FX1 except by the doubler function.

I guess this is why P+S Technik seem to have gone with a hybrid prism and mirror arrangement and have a 21mm frame off the groundglass as I understand their design to be from their website. I guess it took them a lot of R&D to arrive there.

So, the simple home-build erecting version may have hit the resolution wall in terms of how far it can go. The only saviour that I can see may be the wax groundglass which may confer a higher resolution off the available 24mm wide frame. Except for the flickering I know how good these can be.

I did some tests in Kings Park in Perth city today. I can send SD .jpg images to be posted but these are probably pointless except for demonstrating the framing/fields of view/depths of field.

I've sent three jpg images to Chris Hurd with a request if he can kindly place them at www.dvinfo.net/media/hart. These are from the Sony HDR-FX1.

These will have filenames like FX1 TESTS MERGE 01.JPG or similar. This will depend on whether my webmail provider can actually send them on. They are not representative of true resolution as they are frame grabs off downconverted feed out to MiniDV from the camera's HD recording.

Since my wailings about not being able to frame within the prism boundaries at full zoom on this camera on my appliance, I have found that I might just be able to get more than the 24mm frame width if I mount the prisms differently. Presently the frame area is enclosed by support structure.

I can't see them Bob on the site.

Chris advises he is away and will post them after he returns.

Furthur adjustments and tests determine that there is just enough space in the 40mm x 40mm x 56mm 40mm common thickness right angle prism to place a 24mm wide image off the groundglass through a Century Optics 58mm filter mount achromatic dioptre into a HDR-FX1.

The image off the groundglass is effectively cropped top and bottom as the widescreen feature of the FX1 actually sees less of the groundglass than the PD150 at this magnification. You can creep about another millimetre width if you zoom back a fraction but at risk of picking up an edge.

The frame has to be slightly higher and right of centre to clear the apex of the rearmost prism which intrudes into the left edge when the camera is zoomed in. It was this and not a poorly centred lens which created the edge defect.

With the PD150 and its trait of walking across the image towards the right edge when you zoom in, this problem had never become apparent.

If anyone in Australia is making image tubes containing prisms, using PVC 100mm sewer pipe as a case and mounting to camera via a pipe cap, there is another cap which is of a thinner wall thickness than the Iplex caps. They are Ausplastics 100mm dust cap 31.100. The barcode is 9 323745 005552.

These caps are not as robust as the Iplex but are the exact wall thickness to match the channel behind the bayonet lugs on the PD150 and HDRFX1.

If you choose to mount the appliance to the camcorder via the lens hood bayonet fitting, then all you have to do is cut out the matching hole and reliefs for the lugs out of this cap and it will go on snugly without need for filing or scraping the face of the cap.

The dioptre still needs to be attached direct to the camcorder via the filter mount.

Furthur info.

In some real world tests yesterday, in high contrast, low light conditions or late afternoon/early evening, there remained a slight brightness falloff on the left (rear prism) side of the image. Like with a fixed groundglass, the defect is not readily apparent until the camera is panned and the image travels across the frame.

I opened up the path a little more with only 0.25mm supprt remaining to the front prism edge and this seems to have helped. The centering of the front prism apex relative to the edge of the rear prism seems a lot more critical than I had thought. This also cleaned it up some more.

Furthur info.

What I thought was a doubler function on the FX1 which would work like the doubler on ENG cameras is actually a focussing aid only and does not record.

As a potential newscam, I thought this was an excellent feature. So I was wrong.

Furthur to previous posts, I have tried the Nikon SLR lens >> 5 micron dressed groundglass disk >> 40mm x 40mm x 56mm common thickness prism pair >> Century Optics 7+ achromatic dioptre >> combination, as adjusted for the Sony HDRFX1 into a Panasonic DVX100 (PAL) and it seems it should work fine.

The appliance was positioned in front of the camcorder by hand as there was no rear adaptor mount made. In the LCD screen there was a clean image however an underscanning monitor was not used, so what is outside of the TV safe area is not known. Lenses tested were Sigma 50 - 500mm F4 zoom and an older Nikon f2.8 zoom. There was no vignette with these so f1.8 prime lenses should be okay. The DVX100 is an early model with 4:3 CCDs.

PS - Does anyone know how to stop this wretched McAfee Instant Updater phoning home and freezing the screen all the time whilst on-line.?

Sorry for the delay Bob, I will try to get those images up today.

Thanks for keeping this thread alive, it's the one which started this forum!

Chris.

Is no problem. If you can hold on them for a little longer, I've a few more to send which I shall do now.

Regards.

Here's some useless information regarding the AGUS35 - Australian Plumber's Version - Image Erector.

Compared to the SG35, Letus35, Redrock, etc, it is inefficently large because of the CD sized disk. Except for being dropped or run over, I expect it to last a long time as the only fast moving wearing parts are in the motor which runs at about 1500 rpm.

This version does not permit integration of rod style supports through to the camcorder as the disk enclosure gets in the way. The enclosure is also too large to move on top as it then touches parts of the camcorders.

It could be redesigned to work off to the left or right side but would be a bitch to operate handheld because the weight would be way off to one side or the other.

The side view has altered since I began fitting up the FX1 type cameras and I dont have a current accurate view.

The image tube has become shorter in order for the FX1 to "see" more of the groundglass without the prism edges getting in the way. It still works for VX2000/PD150 in this shorter version, in fact better than the original.

From lens hood mount rear face to the AGUS35 Nikon Mount front face is 111mm. The whole thing, including motor, glass disk and 1.5v battery, without lens attached weighs 874grams.

The optical centres as originally illustrated are pretty much as built for the PD150, HDRFX1 and for the the DVX100 they are fine when matched up hand held. The current .pdf files in media/hart are no longer correct for the design and should be ignored.

I have a profile for the DVX100 lens hood bayonet mount but I don't have the correct orientation so will have to inspect a camera again or get somebody at dvinfo to scan or photocopy the hood from the camcorder side to see the correct orientation of the bayonet lugs relative to the set screw. - Any volunteers??

I have tried uploading 5 very short uncompressed .avi clips to the following address.

http://www.putfile.com/bh_107f

They apparently cannot be downloaded and must be viewed off the site . I've tried working them and they don't seem to work but it might just be my mismanagement.

Maybe somebody can give me some advice. All I am doing is becoming frustrated and getting the red mist, which is not good for stress mitigation.

The clips are one from night-vision into PD150 and the rest, tests into HDRFX1. The titles are bh-AR001 to bh_AR005.

Whilst the performance of my version into the HDRFX1 cold be described as adequate, there are other versions which do better.

Regards all.

The clips I sent up which are mentioned in the previous post do not work. It seems I have mismanged them so I shall try again sometime soon.

Today, I took an FX1 attached to an AGUS, down to one of our local TV broadcasters who kindly allowed me to use their Lemac chart.

I put all the Nikon mount prime lenses up at two aperture settings, wide open and f.5.6. Also I tested the 12mm -24mm Nikon digital zoom wide open only and found with careful attention to backfocus and actual focus, this lens can perform as the equal of the others. The f2.8 135mm Auto-Tamron also held up as sharply. This is an old lens of the Adapt-a-matic series not Adaptall.

Tje 12mm - 24mm digital zoom surprised me as my impression was it was a distinctly inferior lens in this application. Against my expectations the 50mm lens at f1.8 suffered the most for being wide open. So much for one's assumptions based on casual observation.

After running the test, I then found, that the vertical and horizontal bar blocks are marked as not resolveable by video which left only the Siemens star focus indicators, the four "eyes" in the corners. These suggest there is little difference between the best resolution off the disk and the camera's own view. However, their appearance fluctuated in a regular periodic beat which altered when the disk motor was shut down.

The hoizontal and vertical bar blocks seem as visible to the camera through the disk image as they are directly. The "B" and "G" blocks yield a moire pattern which suggests they are being resolved. This leaves only the finest "A" and "F" blocks as not being resolvable both via the disk image and direct to camera.

The fluctuation on the Siemens indicators suggests the disk is still running out sufficiently to affect backfocus at HD resolutions. The disk seems to run true by eye match so the issue may instead be end float which in my device is contolled only by the magnetic field of the motor.

There remains an added slightly warm greyish cast to the colour compared to the camera view under the same lighting. It can be white-balanced out.

Constrast seems to be reduced.

The two grey scale blocks at the darker left side of the bar were less separable than in the direct camera view.

View was via the FX1 LCD flipout screen. I have no HD capture facility. The broadcaster did not either as they use their HVRZIUs (similar to HDRFX1) for news in the DVCAM mode.

Lighting was by one 500watt flood which their camera department had just finished using for their own test.

The camera was left in full automatic mode fir all functions.

The test suggests there is room to allow slightly less resolution in favour of a more filmlike image off the groundglass and yet find an acceptable performance into a HD capable camera. This is consistent with Ben Gurvich's observations on the SD footage I have sent to him for comment.

The problem with falloff due to the proximity of one edge of the combined prism path remains for the FX1 which uses more of the area off the groundglass than my own camera, the PD150. I hope to resolve this by using longer but also thinner prisms which should fit into the same workspace as the 40 x 40 x 56mm x 40mm common thickness set I now use.

Images as .jpg files are going to be of limited use as I can only create them via the MiniDV codec. If anyone wants to see these I can post them at putfile if they are requested here.

The news cameraman I spoke to was interested in terms of being able to put long lenses on the HVRZIU.

The above information is relevent only for versions which use the 24mm x 18mm image frame off the groundglass. The FX1 is actually taking a little more width than that and slightly less height at full zoom-in via a +7 acromatic dioptre.

If anone is still building spinners, there is a part which may interest you in terms of setting backfocus and focal plane alignment.

There is a generation of very low cost DVD players which are being found on roadside rubbish collections (in Australia at least) or discards from repair shops as being uneconomic to repair.

Some of the slimline styles with centre trays use a transport, the SHINWA SHD-2502. These have analogue motors for spindle, tracker and loader. The spindle motors have a short shaft, which enables a more compact device. The motors are smaller in profile than older CD player motors but have the same face mount system and centres. The build precision of the shaft to bearing fit is quite amazing.

A bonus is that they have a three axis adjustment on the spindle motor mount similar to the arrangement for analogue tape recorder heads, ie., one fixed screw on a pillar and two adjustment screws which bear against two small but strong compression screws beneath the motor mount plate and secure this to a subchassis.

By cutting away a small portion of the subchassis to carry the motor mount assembly, a precision three axis backfocus and focal adjustment, an adjustable motor mount, ready-made becomes available and requires only simple fitting to a less sophisticated structure. - Epoxy glue even.

The downside will be that being mounted against spring pressure, there is potential for movement if the device is knocked or bumped. However if the DVD players are capable of surviving longdistance transport, I doubt careful use of an AGUS device will make any more demands than this motor mount arrangement can deal with.

These analogue motors may not continue to be available as there seems to be a newer generation of DVD players with brushless DC motors which require a digitally controlled pulse power supply like CR / DVD recorders, burners and scale aircraft electric motors. There remains one analogue motor for the load tray. Removing the spindle from some brushless motors of the outrunner style has proven impossible.

The shaft diameter of the brushless and analogue motors appears to be the same.

I find the availability of spindle hubs a greater difficulty as you only get one for every three motors you salvage.

Good luck folks.

I have again attempted to post short clips in H264 Quciktime this time at this address :-

http://www.putfile.com/bh_107f

The stupid part is I cannot download them back to my email computer as it is a dog. So I can't view them off the web. If ayone actually gets them to work, I would appreciate the advice that they were viewable.

Here follows some furthur useless information for ayone who may be trying to build a plumbers version.

It is a grab from a recent email I sent.

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Hello again.

My diagrams don't show one or two later developments.

Since I fitted up a HDRFX1, I have shortened the length of the image tube to compensate for the thickness of a proper Nikon mount on the front cap and for the FX1 to be able to focus on a wider piece of the groundglass. This involved cutting about 10mm off the front which leaves about 8mm from front of case to front of tube and about 14mm off the back to enable closer coupling of the FX1. The pipe caps themselves now have to be trimmed down as well so they don't fetch up short against the case.

This also involved moving the motor mount closer to the camera by adjusting it with the adjusting bolts to within about 14mm of the front face of the rear prism which was another reason to shorten the image tube at the front. To keep spring pressure I had to put some spacers under them between the front case and the motor mount.

You also need to have a restraining device to stop the disk from moving up and striking the front prism which overhangs it. This can happen if the device gets bumped hard or dropped.

At the Cunderdin Airshow last March, the device dropped off the front of the camera and hit the ground hard while running and shattered the disk and chipped the front prism. I had quickly assembled it with glue tacking, meaning to make permanent screw fitting later and forgot once I had the thing working the way I wanted it. The glue softened in the hot sun because I had the device painted flat black.

There should be a little hook bolt (a cut-down and re-threaded bicycle spoke) from a hole in the motor mount plate below the battery holder and a little to left of the bottom motor mount adjustment stud, - through a hole in the bottom of the case and a small nut or spoke nut to pull up the slack and restrain the motor mount and the disk downwards to keep prism to disk clearance at about 1.5mm.

In the end I got lazy and just glued the adjustment nuts and exposed areas of the studs at the motor mount with lots of silicone bathroom sealer and put a little piece of cardboard across the bottom face of the prism after I set backfocus.

Feeding the bicycle spoke through whilst trying to fit up the motor mount is a real pain.The nut and the spoke end sticking out the bottom is untidy. It also adds complication to the backfocus adjustment and could put it off if the spoke was knocked during use.

Backfocus is easy but has to be very precisely done, otherwise the wide lenses like 24mm, 28mm or zooms will not focus sharply.

All three motor mount nuts are used and interact for backfocus and alignment. The bottom one allows vertical alignment with the lens centre-axes as well as backfocus. . Each side one allows horizontal alignment with the lens centre axes as well as backfocus.

Because the side adjusters are below the image area on the upper half of the disk, screwing the bottom adjustment in (frontwards) actually causes the upper half of the disk to move backwards.This adjustment equally affects the adjustment of both of the other two side adjusters simultaneously.

I set initial backfocus by using the depth gauge of a vernier caliper and measuring from the Nikon mount front face to the front of the glass disk. Because I grind the rear face of the glass closest to the camcorder, the measurement is 46.5mm less the disk thickness which is 0.9mm for my glass home-made disk. So it is about 45.5mm.

I find it helpful when setting each adjuster, to gently press against spring pressure, the motor mount near the nut being adjusted to pop the mount slightly off focus at that point and allowing it slowly to come back onto focus, then snugging the nut up against the plate then letting go. You have to apply pressure very near to the nut as the mount plate can flex if you are not over the spring and the adjustment is then no good.

You need to have a distant defined object like a radio tower on a hilltop and a good tripod for a successful backfocus adjustment, though I have also fluked it by measuring to an object on a wall from the groundglass, then setting the lens to that distance by the number on the lens ring by the same method of focussing the edges of the image.

You check the Nikon lens groundglass image at each edge left and right, top and bottom by using pan and tilt on the tripod to place the same distant object at each of the edges in turn and adjusting the nuts for sharpest image at that point. When you have the edges all the same sharpness, the centre should be correct. When setting this up you need to have the Nikon lens on infinity focus.

If you are in a hurry, then just sharpen the two sides and the bottom edge of the image as you see it in the camera LCD. this should be close eough but not always as good as it can be.

With the FX1, and Century Optics 7+ achromatic dioptre, the groundglass image seems best when it focusses sharp to the camcorder when the camcorder's distance scale reads 1.4 metres in the LCD viewfinder.

The polypropolene sheet (sometimes used as whuiteboard material) is less acoustically live than harder plastics and less likely to transfer motor noise conductively to the camcorder body. It is softer and may change shape over time which means periodic checking of the backfocus may remain necessary.

I try to reduce this tendency by fitting a flat washer on both faces of the motor mount, ie., the spring side and the adjusting nut side. So far, the backfocus has held true during transport and use. It is more likely to go off during a long period of storage. I recommend storage of the device in the upright position so the weight of the motor and disk bears directly along the plate and not frontwards or rearwards through it.

When I update the design I will email the revised pages.


Regards

Bob Hart

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What I forgot to add was that the relay focus has to also be evenly sharp across the image frame. I achieve this alignment by making the three screw holes in the sides of the caps into slots, not round holes, adjusting the cap for best sharpness across the gg after Nikon backfocus has been completed, then snugging down the screws firmly so the rear adaptor which fits up to the lens hood bayonet fitting remains square-on relative to the groundglass.

An update on the image tube/prism block.

The design has been altered to move the horizontal (front) prism apex 3mm to the left as viewed from the rear. The apex of the vertical prism remains the same. The effect of this is to move the falloff area attributable to the horizontal prism apex and vertical prism edge out of the left camera frame as viewed to permit a larger 16:9 area off the groundglass.

This has a side-effect of shifting the frame centre relative to the radius of the disk and may require the image tube centre to be moved about 5mm outwards relative to the disk enclosure.

This is to allow the prism block to be turned anti-clockwise as viewed from the rear, about 7 degrees in the image tube to restore the correct tangential relationship between the lower side of the horizontal (front) prism relative to the groundglass disk.

The two original 40mm x 40mm x 56mm x 40mm common thickness prisms are replaced with two 45mm x 45mm x 65mm x 32mm common thickness prisms, which more closely resemble porro prisms.

To compensate for the added thickness, apex to apex of the two larger prisms, the two prisms are to be installed face to face and fixed to each other by UV curable optical grade adhesive. This will also eliminate a narrow space between the two prisms which is a dust trap and impossible to clean except by dismantling the prism block.

The glass disk I am currently using has a 5 micron finish with a slight backpolish, made using the same method as the original disk which was broken. This disk had been originally rejected as there were defects in the groundglass finish. The defects were larger pits remaining in the finish resulting from the original cutoff process which had not been dressed out by the first coarse grit run. I could be dreaming but the existence of this coarser defect in the finer grade finish seems to produce a slightly better image than my original disk.

Finally, totaly off-topic. The cat (the ginger one in some of the test images) decided my carefully marked out mount mount plates waiting to be cut out from a polypropolene sheet was a ideal place to deposit the biggest furball in the whole entire universe. I didn't see it for two days by which time the biro mark out lines on the polypropolene had become bleached off.

Go ahead and write a novel.
 

Go ahead and write a novel on this subject.

I have been watching your progress in this, thank for sharing!

For those who might be making erecting (flip) versions out of PVC pipe and caps and finding great difficulty in getting the centre axes right. -------------

If you are measuring from the front face of the front cap and the rear face of the rear cap to get them parallel to get the centre axis of the SLR lens, the centre axes of the prism path and the centre axis of the video camera lens all parallel and finding that despite your very precise and meticulous efforts it doesn't hang together right and you get a big soft edge to your images, very likely it is not your fault.

PVC pipe caps like many such injection moulded products have a shape memory. The plastic wants to go back to that it once was, a blob. There are latent stresses within the material and when you cut a hole through it, the cap will deform slightly, most times the centre becomes bowed inwards.

With a non-erecting version, the lens mount will most likely be placed dead centre in the front cap, the camera dead centre in the rear cap and any concave deformation in the cap will not cause a problem as the deformation is centred on the hole.

An erecting version is another matter. The lens mount is likely to be fitted over a hole cut well off centre in the pipe cap. In this instance the centre of the lens mount and the centre of the concave deformation in the cap do not coincide. The lens mount will not be correctly aligned even if the front outer rim of the pipe cap is.

The solution to making sure the lens mount is parallel to the rear cap, is to place a straight edge across the mount face itself and measure back to the rear cap from that. An alternative is to place the device face-down onto a plane surface such as a sheet of glass and with the lens mount face firm on the glass, measure back from the surface of the glass to the rear face of the rear cap.

The caps themselves will be unlikely to be parallel to each other once the face of the lens mount is made parallel to the rear cap.

The rear cap will also present the same problem but the hole for the front-end of the camcorder is much larger and the effect of the deformation less evident. This also only has an effect where the device is directly mounted to the camera via the filter mount of the lens hood bayonet fitting.

Okay! The next question is how do you adjust for the deformation. Fortunately, the deformation across the front face of the caps the caps after the hole is cut is much less than the angle of taper inside the caps where the fit is over the tube. It is a simple matter of skewing the cap slightly on the tube until the parallel adjustment of the front face of the lens mount to the rear cap is achieved. Once the alignment is right, the screwholes are drilled and the screws fitted.

This method is also only known to be valid for Nikon mounts. There may be difficulty with Canon mounts because of the collar on front of those mounts.

Like the rest of the appliance the method is not every elegant but it does work.

A better method of course would be to machine the front face of the cap but then the construction method would have to move from the kitchen table to the machine shop, which rather defeats the purpose of this exercise.

Bob, someone should be giving you an award. Your posts both historical and current are a huge asset/help to the adapter world. Cheers!

Hmmm.... history...

i just love the cigarrette video... i remember that it was like 5am when i recorded it...

I think I can safely say many of us here have a fond memory of that video, too :) That's why I've kept them all... maybe soon I'll do a "history of the 35mm adapter" video for the wiki entry and just for kicks on my site.

Let me know who I'm forgetting, because this is the timeline as I remember it:

1) Agus Casse introduces the idea; made from about $20 and assorted parts from around the house, glued together. Over time, many people contribute to refining this design concept over a myriad of implementations...

2) Alain Aldus moves to the first static design, using aluminum oxide ground glass -- the Aldu35.

3) Brett Erskine schools everyone on the value of condensors, achromats, etc.

4) What is to eventually become the RedrockMicro implementation of the "spinner" styled adapter makes its debut, bringing on the first of the commercial endeavors of many to come...

5) Frank Ladner is the first to successfully employ microcrystalline wax and shows what is in my opinion the best static DIY adapter footage evar.

6) Quyen Le develops, along with Brett Erskine and others at the same time, the first practical oscillating GG device.

7) ...

Agus Casse

Happy to see you around. Do you have anything in your sleeve to influence people here? Thanks for sharing your technics and designs.

Jim Lafferty

Don't forget Dan's works, he has contributed a lot. From number 7 and on, it's hard to come up with anything new unless we have some breakthru technics. All the flipping, relay ... have been on the market and are not new. Hope some of us can someday comes up with something significant, thanks.

Quyen

Agus.

Long time no see.

I seem to recall you were working at a TV station. How is that going? Have you progressed your own device or still using what works best for you?


Quyen.

I think I might have a handle on the ghost image thing some operators are experiencing.

I was doing some outdoors tests with wide lenses trying to wring the last bit of sharpness from them. I happened to pick up the sun through tree leaves and there was its ghost image, shimmering slightly in harmony with a slight runout I am getting with my current disk.

I think it is occurring, on my specimen at least, between the shiny side of the groundglass which faces the front and the optics in the SLR lens.

This might be a case for reversing a popular preference for placing the groundglass surface closer to the camcorder.