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Alternative Imaging Methods
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Old January 18th, 2009, 07:26 PM   #16
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1st Attempt 95% completed

Ok all, here are a few photos of my first attempt at this, I have another vibration motor on the way so I may try that one over the one I have installed now. For the test video I used some scotch tape to hold a piece of GG in place until I get my aluminum oxide power next week when I will grind the piece of glass you see in the photo. I found a cool old 4X5 view camera rail setup to use to mount my GL2 and DOF adapter more permanantly.

The test footage is of my silly 8 year old son and I turned the volume off as my adapter makes too much noise (another minor problem I have to fix). My GL2 was just sitting on a few DVD cases to get it to the right height to use with the adapter. Anyway it is only my first attempt and it was fun to make.

http://cmpritchett.zenfolio.com/img/...32938993-5.jpg

http://cmpritchett.zenfolio.com/img/v4/p577725665-5.jpg

http://cmpritchett.zenfolio.com/img/v6/p703970637-5.jpg

http://cmpritchett.zenfolio.com/img/v5/p841661500-5.jpg

35mm DOF Adapter Test Clip on Vimeo - Test Clip

As always your ideas for improvements are very welcome, thanks to all who have been helping me with this project.
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Old January 18th, 2009, 09:54 PM   #17
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What can I say. The man has become quite seriously hooked and getting there it seems.

The groundglass support pannel appears to be a piece of stiff packaging foam. Am I correct? If so, inspired I think. This is a divergent approach to the Quyen Le method of doing things and looks to be quite viable. I am not sure how long the pillar attach points on the groundglass carrier will endure but it should last awhile with them well outboard like they are and flex occurring in the panel iself.

The video clip is not of sufficient resolution to show artifacts. I think I see bit of CA on the right side in the shiny bit but for early work, on the surface at least, it seems you are well on track.

If your groundglass movement remains not enough and I think it is if you are getting lots of noise transmitted to the enclosure, my next move would be to support the bases of the pillars on three coin sized pieces of the same packaging foam.

This might involve drilling larger holes in the case to allow clearance of the pillars and the little nuts to move or mounting another stiff panel just inside the front surface of the case, high enough to allow clearance of the pillar ends and nuts.

The three pillars at their base ends would therefore be swaying in diaphragm mounts.

Why you would need to do it this way rather than using another single large piece is that a movement of the entire pillar/groundglass support panel assembly must be maintained at right-angles across the optical axis.

A single piece of foam at the base end might allow a rocking motion which would introduce a pulsing soft-focus artifact towards the image edges.

A single piece identical to your groundglass carrier would be okay if you clamped it between two solid panels with clearance holes cut in them where the pillars go through.

This "sandwich' would have to be supported on separate pillars which could do double duty as the bolts which clamp the sandwich together. You would have to experiment with the diameter of the clearance holes. Wider would allow more flex but possibly some movement off the focal plane. Too small would be too stiff.

The only change I would make to your groundglass supportpanel would be to move the motor upward as close to the groundglass as you can possibly place it, to bring its centre of forces inside of the line joining the two pillars each side of the motor.

If you need to lose some weight from the groundglass carrier to increase the movement, I would be inclined to punch or cut out some holes between the top pillar and the bottom pillars. Do not punch out any material between the side pillars and the motor. You need resistive mass to remain there.

Alternatively, you cut a "waist" in the form of a shallow reversed arc away from the area between the top pillar and each side pillar leaving more of a leg shape in the foam on the upper side of the groundglass. Don't cut too much away to make a distinct leg shape because there may be too much flex off the focal plane. You'll probably have to make a few of these to get right.

If the base "sandwich" remains too stiff, you could try a piece of automotive inner tube in place of the stiff packaging foam with smaller clearance holes to stop the tube from sagging, or use electrical passthrough grommets like Quyen does, excepting he uses them on the groundglass panel itself.

I think the inner tube would be fine as long as you use a flat washer on each face to widen the diameter of the diaphragm flex circle around each pillar base attachment point.

I would be inclined to try to support the far end of the motor with a strip of foam tacked on to the motor with a small dob of glue and onto the panel at about 45degree angle. Make sure the glue does not dissolve the foam. The foam may flex and loose some effective movement otherwise. Maybe two more thin strips either side as well to make a sort of tripod to the far end of the motor from the panel but I think one will be enough.

You may need to move you battery pack to make space for pass-through tubes for your support rods you will find you want to add later when this R&D addiction begins to really take hold.

Footnote (The black foam bases in the supermarket meat packs are starting to look a little different now.)

Last edited by Bob Hart; January 18th, 2009 at 10:18 PM. Reason: added text
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Old January 18th, 2009, 10:42 PM   #18
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Thanks for the ideas, actually the GG carrier is made of 1/8" ABS plastic (which is a PITA to cut) I do have some dime shape vibration motors coming so I will try placing one of them closer to the GG. Once I get it mounted on the rail setup I will be able to get the backfocus set correctly. I am afraid that the vibration is not sufficient, so I may go with rubber bushings instead of the plastic nuts where the 6/32 threaded rod meets the GG carrier.

Still a work in progress but I was pleased to get it this far, you all have definatley helped alot. :)
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Old January 19th, 2009, 12:24 AM   #19
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ABS plastic, then I have over-reached myself a little in my comments and overactive imagination haven't I. I am also gullible enough to be sold a canada goose as an airnavigation safety aid.

Back on topic. The 1/8" ABS will be too heavy. Even if you honeycomb it with holes, it may weigh in too much.

Before you go hacking and modding too much, try a piece of that stiff black packaging foam or maybe a meat pack or thin piece of balsawood or thin piece of scale aircraft construction foam. You may have to punch out rather than drill the holes or cut them out with a fine sharp knife.

There may be enough natural flex in those nylon pillars but I think not and your solution of flexibly mounting them is sensible.
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Old January 19th, 2009, 01:48 AM   #20
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A good tone mapping algorithm does two things:
- local tone mapping; dark parts are made brighter and gets increased contrast, light parts are made darker and gets increased contrast, the border between these parts are also enhanced in contrast.
It is a sort of compression method similar to what is done as the first step in mp3, psycho acoustic modeling (removing sounds we can not hear because of other overlapping sound), this is psycho visual modeling (removing contrast information we can not see, to enhance contrast elsewhere).
Tone mapping - Wikipedia, the free encyclopedia

- Blooming, areas in the pixels that are really bright get a halo around them making them feel like they are really bright. Cheap trick, but effective.
http://en.wikipedia.org/wiki/Bloom_(shader_effect)
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Old January 19th, 2009, 10:17 AM   #21
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I get what you are saying, I see now that I have constructed it how light it really needs to be to get the vibration to be effective. Do you think a piece of foam core board would work? It is really light and stiff and comes in black.

This is the stuff I mean: Foamboard

I just dont want something that is going to wear out quickly with the vibration and get the focal plane out of whack.
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Old January 20th, 2009, 04:46 AM   #22
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The stuff you linked to has a goldplated price. I doubt it would be as flexible as stiff packaging foam. You would be back to adding flexible joints on each end of the pillars.

If you have an old (ACCODATA brand) black foam bluecovered computer mouse mat, try cutting a piece out of one of those to see if it will work. The groundglass itself will add stiffness if you glue the edges firmly into the mousemat foam. If it tends to slump out of shape, maybe a bit of stiffening cardboard around the groundglass would help.

There would need to be a bit of stiffening of the foam around the motor. Maybe infusing some hardening glue into the foam where you want it to become hard would do the job and just leave a flexible area where pllars come through, about 1/2" to 5/8" in diameter. too much glue however might add unwanted weight.

Maybe a 1/8" hardened strip around the outside rim or thin carboard glued on flat around the edge. The groundglass glue should look after the centre. Maybe a few 1/8" wide crisscrossed lines across the foam would keep it straight.

I am just being plain cheap and stingy here but it was an interesting alternative path you led me down and like a pup with a rag, I don't want to let it go just yet. To prototype the idea, I would be tempted to use foam meatpacks first to sacrifice until you get the final pattern right.
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Old January 21st, 2009, 06:23 PM   #23
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Took the plunge - Bought a Brevis35 Rev2

Well I am continuing to work on my DIY 35mm DOF Adapter but found a super deal on a Brevis35 Rev2 with Cavision RS15IIM ROD Support System and got the seller to throw in a Nikkor AF 75-300mm (which I will sell on ebay to pay for a prime). I got it all for $675 shipping included! Cant wait to use it...
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Old January 25th, 2009, 04:08 PM   #24
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Finished Product

Well I replaced the 1/8" ABS plastic GG holder for a black meat packing foam GG holder. I also am using a small dime sized pager motor instead of the barrel type I had. I found a base from a home made 4X5 view camera and modified it with a riser for my GL2. I just used some oak and aluminum stock with hardware (all from Lowes for $25) to make the adjustable riser. I got a sheet of self adhesive foam to put between the riser and my GL2. I am also using a portable TV I got from ebay for $51 shipping included instead of a flip module. The tv has the ability to flip the picture upside down or reverse it so it works well.

I have a Brevis35 rev2 with Cavision carbon fiber rails setup in the mail but it was fun to build this one and it is working, although I fear not as good as the brevis35 will :)

Check out this short clip and photos and let me know what you think!

Home Made DOF Adapter Test Clip - Final on Vimeo

http://cmpritchett.zenfolio.com/img/v6/p207330291-4.jpg

http://cmpritchett.zenfolio.com/img/v5/p270635116-4.jpg

http://cmpritchett.zenfolio.com/img/v4/p110787839-4.jpg
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Old January 25th, 2009, 07:42 PM   #25
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It is a little hard to tell from the vimeo clip but it seems you are getting enough groundglass movement to randomise the groundglass texture. So the journey is complete.

It is far from a pointless exercise because you will have all the understanding, practical and theoretical (well almost) that you need to work Dennis' adaptor to its best.

The name of the game now is practice > practice > practice, to suppress all those conditioned reflexes you have aquired from operating the video camera alone and develop a new Brevis based specific reaction to setting up a shot.

Once that has become instinctual, you will look back two years hence and be quite amazed at just how far along your own skillset has come because you will force yourself to develop in other areas.

The groundglass adaptor is not a magical cureall for all the ills of 1/3" camera imagers. It puts up quite a few hurdles of its own but it does open a major gate in way of your creative progress.

Enjoy.
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