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Old May 6th, 2008, 02:54 AM   #1
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DIY Flip module

Hi Guys

It's been a long time since I've visited this forum and am surprised how few posts there are compared to the hundreds there were a year or so back.

I've tried searching ( Before anyone suggests) and can't find any info on a DIY flip device.

I remember how open the forum was for info sharing back when.

I wondered if anyone had any info for a DIY flip thingy?

Thanks in advance Stephen
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Old May 6th, 2008, 06:48 PM   #2
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Common erecting (flip) paths used in adaptors :-


P+S Technik, Letus, SGPro, Brevis??

Optical centre axis >> first 45degree reflector bounces left 90degrees >> second 45degree reflector bounces up 90degrees >> third 45degree reflector bounces right 90 degrees >> fourth 45degree reflector bounces rearwards 90degrees.

AGUS35 APVE - homebuild and possibly others.

Optical centre axis >> first 45degree reflector bounces up 90degrees >> second 45degree reflector bounces forward 90 degrees >> third 45degree reflector bounces right 90 degrees >> fourth 45degree reflector bounces rearwards 90 degrees.


The first arrangement is the more practical and better method and returns the image to the camcorder along an axis vertically higher but on the horizontal centre.

The second arrangement can be made more compact front to back but is less suited to oscillating groundglasses as the second and fourth reflections pass forward and return across the focal plane.

The Mini35 uses three 90degree prisms plus an adjustable surface coated mirror for the third reflective surface.

The earlier Letus arrangement was four surface coated mirrors. Most recent arrangement is believed to be prisms.


The Agus35 APVE arrangement uses two 90degree prisms in a modified porroprism setup. The use of two single prisms limits the practical size of the image path as custom prisms are needed.

This arrangement can use two identical prisms or two individual custom prisms of different sizes, typically one short and wide, the other thinner and longer.

This arrangement can be made to return to camera above the vertical centre axis however the size of the prisms required to do this is impractical and the four prism or prism-mirror hybrid would be better adopted.

My current arrangement returns to camera both higher and to one side of the original centre axis. Here is a link to an early experiment.

http://www.dvinfo.net/media/hart/Agusmir1.jpg

This arrangement throws to the left in the first stage and rearward in the second. Don't use ordinary mirror glass except for proving layouts as there are internal reflections in the thick glass which spoil the image. Surface coated mirrors or prisms are the only way to go. The corners cut out of tissue cartons make handy 90degree jigs for quick experiments.

Last edited by Bob Hart; May 7th, 2008 at 07:45 AM. Reason: added link
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Old May 7th, 2008, 12:26 AM   #3
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One idea I had was to take a duplicate piece of optics inside the 35mm lens which flips original image to re-flip it. I held two SLR lenses together and it seem to work. I'm guessing there's many problems with this method hence why all the major adapter makers went with prisms. I'm just curious as to what those problems might be. Someone said it is too small. Anyone else tried this or have any idea why it wouldn't work?
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Old May 7th, 2008, 01:40 PM   #4
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Thanks Bob

Glad to see that some of the good guys are still happy to share information.
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Old May 7th, 2008, 10:37 PM   #5
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There is a bit more info to be found in the files near the top of the index here :-

http://www.dvinfo.net/media/hart/

I do not generally publish their existence as they are old designs and will take you down a partial dead-end if you build to them. I have not redrawn the evolutions which subsequently occurred.

The mods were to use phenolic board instead of craftwood for the "parterpanel" as I then called it. Craftwood simply was not strong enough and was about as dimensionally stable over time as sugar in hot coffee.

If I could conveniently get hold of it I would use the Delrin type machineable plastic. This stuff will confer a little shock dampening which is a good thing when supporting brittle glass.

I used a vertical mill to cut the channels for the prisms and clamped them across the "point" of the 90 degree corner. Use a hard cushion of thin cardboard as the glass is verty brittle and will flake.

I ended up placing the prism hypotenuse faces at 1mm separation with a gasket to keep out the dust as cleaning that narrow gap is hard.

With a 4+ dioptre, it is possible to have the prisms completely behind the groundglass which would permit an oscillating groundglass a la Letus or P+S.

For final alignment, the 3 screwholes holes cut on radial centres in the image tube are drilled oversize to allow some movement until the screws are tightened down. The screws match into holes in the "parterpanel" which is a snug fit in the tube.

I used flathead self tapping screws but these are not really satisfactory for permanent fixing as they will wedge the phenolic board apart and become loose.

I only use them to secure a final adjustment then use beads of semi-hardening white bathroom sealer to tie the thing together. It does not let go but can be picked away with a small screwdriver if it needs to be pulled apart.

P+S have used a different approach with the MIni35. Their prisms and mirror, mount to a common plane which forms the rear cover and the bayopnet fitting for the relay lens attachement. The assembly is fastened into the case from the rear.

The original Letus flip module is machined from a Delrin type plastic material in two half shells which each support an entire mirror and share support of two.

All the mounting angles are internally machined and the mirrors are bonded by end edges, not entirely across their rear faces or side edges. This bonding method appears to be driven by the design which requires the front and rear mirrors to be inserted into the assembly after the halves are joined.

The bond material is a semi-hardening stiff adhesive. Bonding just the ends of the mirrors is a good method.

Any dimensional movements of the Delrin halves due to the clamping pressure of the two screws or heavy-handed forceful mounting on some home-made bridgeplate and rods system is less likely to damage the mirrors.

Quyen has since moved on to a machined metal enclosure for the Extreme. I have not studied it but published images suggest a single end piece carries all mirrors or prisms.

Quyen's design requires good machine operator skills as the right-angles are cut laterally in the two half shells. My arrangement relies on existing parallel faces for reference.


For a better look at my design go to this YouTube clip :-

http://www.youtube.com/watch?v=CnweOEEqlRY


For a look inside Quyen Le's original Letus35XL go here :-

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



FOOTNOTE: I think I may have had a memory lapse relating to the Mini35 as to which reflecting surface is the mirror. I'm not about to go find one to pull it apart to find out again. I think it may have been the first. not third as I state in my post above. Doesn't matter as the principle is correctly described.

Last edited by Chris Hurd; May 8th, 2008 at 09:00 PM. Reason: added text
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Old May 8th, 2008, 08:45 PM   #6
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Our flip solution started life as a mirrors based setup and was scrapped before hitting market due to what we projected would be problems with dust, alignment and light loss. What we're currently shipping is a fully CNC machined housing, in annodized aluminum, containing a prism assembly. It starts life as a brick of aluminum and several blocks of raw glass. The optics are modular meaning there is zero possibility of misalignment or contamination. A carefully compensated, fully coated, 72mm achromat is provided on the assembly...which can be removed and used as a very high quality macro lens for both video and still cameras. This achromat is computer modeled and tested to maximize contrast, reduce CA, and provide nearly perfect edge to edge sharpness.

I'm a huge fan of DIY solutions but the our flip module is simply impossible to duplicate as a one-off DIY. At it's price, I'd consider it an incredible value for use with any DIY adapter though :-) 62mm threads are provided on our interface ring for just this purpose.
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Old May 8th, 2008, 10:26 PM   #7
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I would endorse Dennis' comment. With my own project, I arrived at a solution for the PD150 by a mix and match method using available hardware and optics. Then along came the Z1 and it was back to scratch again.

All up costwise, by the time I got it close to sorted, it would have been cheaper to buy in any one of the alternative flip adaptors.

I am not about to discourage home-builders, however making a flip module definitely requires more than kitchen table workshopping.

Slightly digressing, I tried making a simple frame for a home-buildable flip module using a complex one-piece folding of a cutout from galvanised steel sheet. Anybody with a half decent pair of vicegrip pliers, tinsnips and two short pieces of bed iron as formers could have made it.

Worked too - until the disk motor started up. Now I know how they did the earthquake shake effect on the movie "Doc Savage. Man Of Bronze".

Out of curiosity Dennis, did you end up using UV cured optical adhesive to invisibly bond any of the matching prism faces for less light loss?

Just reading back on previous post, I just discovered how well I can do it wrong so here follows a correction :-

QUOTE:
The first arrangement is the more practical and better method and returns the image to the camcorder along an axis vertically higher but on the horizontal centre.
END QUOTE:

REDRAFT:
The first arrangement is the more practical and better method and returns the image to the camcorder along a parallel axis, directly above the entering optical centre axis of the lens on front of the adaptor.

Sorry for the misleadings folks.

Last edited by Bob Hart; May 8th, 2008 at 10:34 PM. Reason: added text
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Old May 9th, 2008, 06:34 PM   #8
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Our prism array is effectively one piece..how we got there is a detail I woudn't share publicly. Getting everything to spec was an incredible challenge as we work to tolerances in the thousandths of an inch range. The equipment used in manufacture, tolerances observed, and even assembly is a process completely out of the realm of DIY. Factor in the achromat we include, and the price becomes pretty hard to argue with.

Bob, I'm hoping we can hook up some day across the continents so we could give you a personal tour. No one deserves it more than you :-)
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