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Old September 4th, 2005, 12:49 PM   #16
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Glen,
Thanks very much for your input. Centring the glass is ofcourse the hardest challenge. Your second sujestion is not far off from my method. I have uploaded 10 diagrams detailing my method on my other thread:

http://www.dvinfo.net/conf/showthread.php?t=50507

But i think your sujestion can be added as a last step to my process. I was thinking of using sandpaper to do the same thing to finish up, but a fine sharpening stone with lots of oil would be much better.

If we can please continue the spinning mechanism discussion on the above thread.

Again, thanks for your input, very helpful.

Wayne.
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Old March 14th, 2006, 08:43 PM   #17
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Wayne, can you explain why this happens? I am wondering why the aerial image cannot function in place of the ground glass. If you were to place the 35mm lens, then an achromat, why couldn't a camcorder record the aerial image off of the achromat without losing the DOF properties of the 35mm lens? I am really curious about this so any help would be great. Also, in your example clip you had the camcorder recording the ground glass directly, right? No other elements were between the camcorder and the ground glass, right? Thanks for your help.
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Old March 15th, 2006, 05:07 AM   #18
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Wow, my old thread, hehehe.

I certainly dont have a degree in optics, but its all down to taget size (size of the senser). Without any GG, the image will be projected directly onto the cams small CCD (through its own lens first, ofcourse). Because of this, there will also be a 7.2x magnififation. Now, with the GG in place, the lens is projecting its image into a bigger target size (36x24mm) that the lens was designed for, and the DOF properties are retained. The camcorder then simply records this projection from the other side. Its just like the camcorder recording any other image, the DOF has already been rendered.

Its like taking a still image with your 35mm SLR cam, getting the picture back from the developers and then taking a picture of this with your camcorder, the DOF is already a part of the picture (or already part of the projection, in the case of the adapter).
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Old March 15th, 2006, 10:55 AM   #19
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Thanks for the reply Wayne. I thought this was going to end any possibility of grain and light loss, but the idea has been disproven. I'm glad I found your test video first though. Your explanation makes sense, but I sure wish it had worked.
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Old March 15th, 2006, 10:58 PM   #20
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mike, you can record the image straight from the slr lens with no gg. but like Wayne said, your still getting the same dof from your camcorder even without the slr lens. The only thing your doing is flipping your image. and without your gg. your acomplishing nothing. just a reversed image.

WAYNE!!!!, looking at your intitial test with the acid etch and the vaseline looks amazing. thats almost no light loss at all! can you tell me what type of acid cream you used and why did you have to rub vaseline over it. do you rub on the vaseleine after youve etched it, rub off the excess, and use stick it straight into the adapter without any type of seal? thanks. Im going to build a spinner and i was thinking about going for something like 220 grit ground glass. but your test shows practiliy the same amount of light with the aerial image off the slr. thats something i didnt think was possible without going for the expensive beatties. thanks in advance
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Old March 16th, 2006, 06:13 AM   #21
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Hi Forrest,

Yes this was some time ago. I used standard 'Armor Etch' cream to etch the glass. Once the cream is washed off with water, the vaseline is then rubbed on the etched side and then wiped off with a soft cloth. This gives a perminant 'wet look' and is the reason for the low light loss in that test.

Stay away from the acid etch, though, as its impossible to etch evenly and uniform. The vaseline worked the same with an aluminium oxide grind. When the SG35 was being shipped with a glass disk (most of the online footage) it was either a 320 or 180 grit grind, with the vaseline treatment. It really improves light transmittance without really compromising diffussion. The low grit size will ensure NO GHOSTING.
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Last edited by Wayne Kinney; March 16th, 2006 at 07:02 PM.
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Old March 16th, 2006, 04:39 PM   #22
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Awesome Wayne, i tried this on a ground plastic cd i made this morning, and it works great! Does it effect the diffusion of the glass, or is it just the same diffusion, but with better light transmission. Wayne, it seems you have made an extrodianry substitute to the beattie. And especially for spinning adapters because you can get rid of grain and dust. are there any con's to this type of setup, becuase i havent seen any yet. and if there isn't, are you selling your SG35's with this type of vaseline glass, bbecause you should be rich.
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Old March 16th, 2006, 06:31 PM   #23
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Forrest,
OK, i have sold units with this setup, and im glad you see the same results and enthusiam as i did when i found this out.

I have actually now found a material that has the same properties as the glass with vaseline applied, but its like this stock, so no vaseline, but with even better diffussion. This is whats now used on the SG35 and SGpro.

Quote:
Originally Posted by Forrest Schultz
Does it effect the diffusion of the glass, or is it just the same diffusion, but with better light transmission
It does effect diffusion slightly, but its small, and the extra light transmittance and contrast is worth it!
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