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Old December 31st, 2003, 03:33 PM   #61
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From what I understand, the 1 micron and smaller grain sizes are all diamond... at least that's all I've been able to find that small. In the article Vendible just mentioned, it says diamond is too hard on the glass and causes big gouges that are easily noticable in the image. I've been thinking about giving it a try anyway, just to see what happens.
http://www.facetingmachines.com/polishes.shtml has some very fine diamond compounds, sprays, and slurries (dust & lubricant). Appearently, these are used for polishing purposes. Basically we're trying to get as close as possible to polish without actually polishing the glass. So maybe 3 micron is the best option until Vendible finishes his experiments with the coating he bought.
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Old December 31st, 2003, 03:36 PM   #62
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Ideally, we'll be able to grind/coat the flat side of the first plano-convex condeser lens. That would eliminate the plain piece of glass but accomplish the same result (much like the SLR's ground fresnel lens).
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Old December 31st, 2003, 05:30 PM   #63
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upside or not?

<<<-- Originally posted by Vendible Book : Filip,
Actually the image produced by the 35mm lens is both upside down and left-right reversed.

>>>>---

i think you are wrong on this. maybe i do not understand something, but if you extract (in SLR cameras) mirror, and penta roof prism - what you get? just the image which is upside down. i just took the lens from my AGUS35 and looked thru it - yes, it's of course upside down, but when i turn my head upside down, i can read everything thru this lens. i also tested it with frosted CD (just to be sure everything is checked) - and the image is still upside down. but not reverted left-right.

>>>>>>-- (Vendible's quote)
right. A dove prism only inverts the image up-down, not left-right.
>>>>>>>

so if above is true for dove prism (i cannot check it right now, i beleive i will found it in next few days, when i receive dove for testing) - that means - no need for pentaprism, roof or no roof.

>>>>>>-- (Vendible's quote)
Honestly I don't know much about the film/cinema frame spec. I only see the standard 35mm camera produces frames of 24x36mm. What kind of lens do you use for half of that frame? -->>>

i didn't thought about any specific lens. i'm using "normal" 35mm still camera (read cheap) lens for testing etc.
i just said that film frame dimensions are:

1.33 Full Gate 24x18mm

(1.33 stands for proportion of the frame - 24:18)

that is two times smaller then normal 35mm still cameras frame, so this means that we can still zoom into it and to have proper image - compare to film (cinema) frame size. and if you are talking about roof prism and your experiment - even with the smaller frame - it is possible to reach film look... i hope.


filip

p.s.

happy new year
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Old December 31st, 2003, 05:43 PM   #64
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16 mm C-mount trials

The home-made ground glass instructions are interesting, and they've inspired me to return to an abandoned project. For a while I've been playing with a C-mount adapter - like a 16 mm version of the 35 mm adapters. The depth of field is, of course, greater with 16 mm than with 35 mm (especially full-frame) but you can get very fast 16 mm lenses - 25 mm f/0.95 and 16-44 mm f/1.1 for example.

The other advantage of 16 mm is that it is easier to avoid darkening around the edges of the frame. A 20 mm diameter plano-convex lens can be used as the condenser. I've got my system to work with an aerial image (ie no GG), but the penalty is great depth of field: the video lens can focus the 3D aerial image too well.

Apart from a shortage of spare time, I've been putting off grinding the plane surface of the condenser because I didn't think that I could do it well enough. Having read Vendible's posts, I now feel like risking it - testing on a piece of plain glass first.

My existing adapter works with an image about 10.5 mm x 8 mm - just larger than full-frame Standard 16 (most Standard 16 lenses will cover a little more than the full frame). If you divide the frame height and width by 3 microns, you get about 3500 x 2500. That seems to suggest that the grain should not be visible if there is no light shining on it other than from the image. I'll test first, because it seems to good to be true and I wonder why it was visible when Vendible tried it with a much larger frame.

The final part of the adapter is a Hoya 10 diopter 55 mm c/u lens. I got the standard C-mount parts, condenser lens and mount from Edmunds.

Best,
Helen
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Old December 31st, 2003, 09:59 PM   #65
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Helen, what focal length condenser lens will you be using? are you planning to use a fresnel and condenser, or two condensers?
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Old January 1st, 2004, 03:17 AM   #66
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Nicholi,
The current version has a single 20 mm focal length, 20 mm diameter plano-convex condenser.
Best,
Helen
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Old January 2nd, 2004, 01:04 AM   #67
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I have posted my new design
http://f2.pg.photos.yahoo.com/ph/lou...=/35mm+Adapter

The cost of making these plastic parts for prototyping will cost over $250, ouch. I guess I'll make my hardboard version first.
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Old January 2nd, 2004, 01:48 PM   #68
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colonia35 zenit
my footage from january 01.

look

http://www.moorefilms.com/dtest.htm

to me it looked GREAT.

the best i can get from a trv18 with the 35mm adaptor.

ciao
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Old January 2nd, 2004, 08:04 PM   #69
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OK, it's finally here! This new material I have been talking about is the Holographic Diffusers.

Benefits:
- High diffuse transmission efficiency (over 90% light are transmitted)
- Very high diffusion quality, details are not blured! At the same time, the hot spot problem is gone, no fresnel or condensor lens needed. (Can you believe it?)
- Very thin (less than 1mm thick) and flexible

I was hesitate to tell people because it's not cheap to test them out and there are many varieties of it. I have a picture of it with my other parts here

http://f2.pg.photos.yahoo.com/ph/lou...m=DSC00142.jpg

It's certainly better than any of the ground glass I have seen or made, even the 3 micron ones. I don't have a footage yet. But I have seen what it can do and I'm very excited. People probably aren't willing to spend $100 for a 2x2in piece at this point, since you haven't seen anything made from this material.

Edmund sells this kind of diffuser (but I didn't get it from them). See http://www.edmundoptics.com/IOD/Disp...Productid=1363

It's going to take me at least a week (2 weeks more likely) to complete a prototype and shoot some videos. Another reason you might want to wait is if it's good enough, many people might want to buy it and I can get them at a much better price.
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Old January 2nd, 2004, 08:52 PM   #70
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That's excellent. I will admit I've been a bit hesitant to buy everything for grinding glass just in case your diffuser idea worked. It sounds very hopeful, good luck with the prototype.
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Old January 2nd, 2004, 09:21 PM   #71
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A note about Holographic Diffusers, they are very easy to scratch, must be handled VERY carefully. Try not to get your figure prints on it and don't try to wipe it with cloth even if it's soft cloth.

If anyone is interested to order this together, please let me know. I can get them at OEM price of $50 each 2x2 inch piece if there are over 25 orders.
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Old January 2nd, 2004, 11:08 PM   #72
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You already got the stuff... what dispersion angle did you get? I have been in contact with the company for about a week and a half... so far it seems the best angle is 80 degrees for complete elimination of vignetting over the entire 35mm frame...

Anyway, I certainly would be interested in getting an OEM price, as I was considering getting the stuff anyway...

What are the prisms that you got there? Once you get it all together would we be able to bulk order them also for that OEM discount?

I'm really anxious to get this all started, especially as I got a short film to start shooting in about 2 weeks.
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Old January 2nd, 2004, 11:28 PM   #73
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Louis,

How thick is the diffuser itself? You have said that the material is less than 1 mm thick - but is the diffuser a thin coating on that, or is the diffusion medium that thick (like opal glass)? I'm asking because I suspect that it is very important to have an extremely thin diffusion layer (ideally infinitesimally thin), otherwise the image will be soft. Is it a very thin layer of photopolymer on a thicker substrate? It sounds ideal.

I'm also surprised that you don't need a condenser - that baffles me a little, but it is late after a heavy day. Are off-axis rays diffused towards the axis? Magic indeed!

Best,
Helen
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Old January 2nd, 2004, 11:51 PM   #74
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Helen,
The whole diffuser is 0.1 mm thick, the coating (diffusing) surface is much thinner. I mentioned before that the feature size of it is about 1 micron.

Nathan,
This Holographic Diffuser (HD) is very interesting, the one I have is the 80 degree version. After some test, I'm very happy with its diffusing ability, since it completely removes the hot spot problem by itself without any help from condensor lens. The quality of the image is superb and there is no visible grain.

The diffuser itself transmits over 90% of light, but this 80 degree version diffuse light to all directions within 80 degree, that's a lot of light going everywhere. So comparing with a fine ground glass I have, the camera actually see a darker image with HD.

I want to get one with 10 degree or 40 degree to see if they will direct more light into the camera. The only thing is, I was told that with the smaller degree, the feature size goes up (up to 10 micron). But I think it's worth a try before we decide which one to order.
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Old January 3rd, 2004, 12:23 AM   #75
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Louis,

Given the nature of the 'features' I wouldn't be surprised if you could get away with them being 5 to 10 microns without them being visible to a miniDV camera (when the image is 24 x 36 mm). After all, 36 mm is 3,600 units of 10 microns - about five times the number of pixels across a DV frame.

This appears to be the magic bullet - well worth 100 dollars a sheet!

Best,
Helen
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