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Old December 21st, 2004, 01:49 AM   #61
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I don't think you have to post uncompressed video. At SD res I think you will find 10 megabit/sec media 9 videos will preserve all the grain or lack there of. I used a bit less than that for 720 P and it holds up well. Well enough for HD dvd's too, the industry shows. Take the T2 special edition for example.
So how about a media 9 vid!
-Les
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Old December 21st, 2004, 09:15 AM   #62
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Brett.

Off-topic. The camera tech who showed me the dove prism also asked me why I was using 35mm still cam lenses when medium format would be so much better.
(He has a store full of medium format stuff he wants to move of course but he made the same point as you do. If one wants HD resolution then one must use the scaling effect of a larger format and gg screen area to reduce the grain proportionately, also the inherently better resolution of the larger format).
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Old December 21st, 2004, 09:44 AM   #63
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Medium format does seem very promising Bob - even with the slightly slower lenses.

How much light do you loose with your system Dan?
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Old December 21st, 2004, 10:42 AM   #64
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No hard feelings,
just hard work.
Use the camera (camcorder)you have, aim at a scene and take a reading (ex: 1/60 5.6)
place a lens and a focusing screen of an SLR infront and take another
reading. ( It doesn't show a loss over 1/3 stop or less here)
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Old December 21st, 2004, 11:20 AM   #65
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Check out my link for more info but heres a quick overview:

Expect MOST MF lenses not to open more than f2.8 while in 35mm most lenses open up to around f1.8-2.0. There are special cases for both formats of coarse but these are generally what your going to get in the affordable lenses.

Now I know what your thinking...MF lenses sound like they are up to 2 stops slower than 35mm lenses. Why would someone want to use them...? Well consider this. Because the image they produce on the GG is so much larger you wont have to zoom in with your video cameras lens to see it full frame. And as many of you know if you zoom in on most video camera lenses you start losing stops (ie DVX100 is only a f2.8 at full zoom and a f1.7 at fully wide). So if you dont have to zoom in you just gained back any light loss in the system. Basically your in the same boat in that sense so no additional light loss problems.

Next DOF. DOF is even shallower in MF versus 35mm. The DOF of a MF lens set at f2.8 will be very similar to that of a 35mm lens set at f1.8. So once again no problem there.

Now on to the advantages. Since your no longer trying to capture such a small image on the GG you dont need a diopter anymore. Anyone thats been experimenting with diopters knows that the inexpensive ones have major color fringing problems that severely effect the final image quality. While the achromat diopters work much better but one thats both strong enough and of high enough quality are very expensive. So with a MF DOF adapter you no longer need a diopter. One less piece of glass to worry about.

Next because you have a larger image on the GG in MF you can expect to see a increase in clarity and a image thats less diffused.

Once again Dan's adapter might already be clear and sharp enough so all of this might not be necessary. But if it isnt, I personally feel he can improve his incredible adapter even more by switching to MF lenses. Thru building many versions of a 35mm adapter and watching the footage posted by others online its been my experience that the footage has always been overly soft. To the point its draws attention to itself and wide shots loss some important detail. Try shooting the same shot with and without your adapter to see what Im talking about.

Anyways this is one way to get around that problem but I also believe with enough searching its possible to find right type of GG with characteristics that would allow someone to pull a pretty sharp image out of a 35mm adapter. Look at P+S Technik. They look pretty good. Not perfect but close.

Anyways something for everyone to consider.
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Old December 21st, 2004, 11:20 AM   #66
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<<<-- Originally posted by Dan Diaconu : No hard feelings,
just hard work.
Use the camera (camcorder)you have, aim at a scene and take a reading (ex: 1/60 5.6)
place a lens and a focusing screen of an SLR infront and take another
reading. ( It doesn't show a loss over 1/3 stop or less here) -->>>

No offense,

Show me the real demo.
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Old December 21st, 2004, 11:39 AM   #67
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<<<--
Originally posted by Brett Erskine :
MF - Anyways something for everyone to consider.
-->>>

I know I got pretty excited when I pointed my camera at my Mamiya RB67 GG the first time. I ordered some satinsnowglass gg in that size so I could try it out. I still had vignetting and grain issues though the images did show some real promise.

You may be right, Dan's design with a MF lens and bigger GG might be the ultimate... especially when moving towards HD.

If systems like the Kinetta get cheap enough it may be moot. You can slap a 35mm lens right on those.
http://www.kinetta.com/download/files/kinetta-camera-brochure.pdf
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Old December 25th, 2004, 04:27 PM   #68
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About the preivious "method" to determine the light loss:
Sorry, I did not express the test clearly:

The 1/60 @ 5.6 (or anything else suitable for the avail light) I was ref. to, was the reading on the camcorder /digital still.
The lens I used (and did not see much light loss) was Nikon
1.4/35 and Minolta 1.4/50 projecting the same scene image on the GG.
Camcorder zoom matched the focal lenght of the SLR lens, in both cases.
(so the same amount of reflective light from the same scene
would be compared) : direct reading vs. 1.4/50 lens on the GG.
I am sure a light meter would be more accurate in reading,
but I did not care to find out the actual loss since I do not know of anything brighter than Beattie.
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Old December 25th, 2004, 04:35 PM   #69
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Quote:
but I did not care to find out the actual loss since I do not know of anything brighter than Beattie.
A holographic diffuser
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Old December 25th, 2004, 07:10 PM   #70
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http://www.globalspec.com/featuredproducts/detail?exhibitId=3781&fromSpotlight=1&fromSupplier=0
http://silver.neep.wisc.edu/~lakes/HoDifLoScat.pdf
http://www.poc.com/lsd/default.asp?page=applications&sub=hdst
http://www.photonics.com/spectra/applications/XQ/ASP/aoaid.313/QX/read.htm

As far as I understand from the above (and other sources)
this is (in simple words) a "linear" Fresnel, used in LCD screens (and other applications) to even out the light from the
(usually two on the sides) light sources found in LCD's.
The light loss (towards the center of the screen with the square distance from the sources)
is precisely matched and compensated by the amount of
reflective surface: the further away from the source, the
bigger the reflecting receiving tip of the prism. End result;
evenly reflected light of a surface from the same linear source.
Did not try them, but I do not envision them transmitting more light
(from a centered light source such as lens) towards corners than the same thing
made specifically for the purpose (such as Fresnel in Beattie screens)

If you find them brighter, side by side measured, let us know.

PS. Same idea used here
http://pictures.care2.com/view/2/836676796
to even out the screen (from 3 LED's) of a "bomb detonating watch"
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Old December 25th, 2004, 08:37 PM   #71
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Merry X-mass, Happy hanukkah and
a happy new year to all members and guests.
(better later then never, I guess...)
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Old December 26th, 2004, 03:47 PM   #72
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Dan,

Unfortunately I do not have a beattie screen to run tests with.

Holographic diffusers can have a trasmittance greater than 90%. I would be very surprised if any GG or screen could match that.

I'm not entirely sure what you mean by a "linear fresnel" but these diffusers produce a highly homogenized light ouput. The direction of the initial lighting is not important. In addition to this you can use these diffusers to redirect the light in numerous directions and shapes. Very cool stuff!

From the POC website (the company who holds the patent):

"Light Shaping Diffusers are holographically recorded, randomized surface relief stuctures that enable High Transmission Efficiency (up to 92%), and Controlled Angular Distribution, while providing high quality Homogenized Light. These fully randomized (non-periodic) structures are non-wavelength dependent and will eliminate moiré, without chromatic aberration. The precise surface relief structures provide controlled angular light divergence, emulating a negative lens.

Standard and custom OEM products are available, including a variety of angles, sizes, shapes, cut-to-print parts, and substrate materials including 2-sided diffusers (PCS), variable angles, color tints, and low birefringent substrates."
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Old December 26th, 2004, 05:33 PM   #73
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Aaron,

I am just as curious as you are to find out the dif (I am sure there is
a BIG one)
Do you get a "hot spot" in the centre? (using a wide 20-28mm lens)
on a 24/36mm surface? (I would be surprised if you would not)
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Old December 26th, 2004, 05:43 PM   #74
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poc site

Aaron,

i checked poc site:

http://www.poc.com/lsd/default.asp?page=overview&sub=main

and read what you already mentioned. did you chcecked that more deeply? i'm not expert on this - but which one diffuser is sutable for our GG works - in your opinion? any of the mentioned there on their site, or it shlould be custom made?

thank you,

filip
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Old December 27th, 2004, 11:01 AM   #75
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Dan,

I don't know if there is a big difference or not. It would be great to find out but I just don't have the necessary supplies. I'm not here to say that beattie screens are worst than holographic diffusers so you have to go with one or the other. I'm just passing on some interesting knowledge I've gathered.

From an online article regarding holographic diffusers:

http://www.mdatechnology.net/techsea...p?articleid=33

"The holographic beam homogenizer is a thin sheet of material that diffuses light. Placed between a light source and a display, surface, or screen, the homogenizer eliminates “hot spots” (bright concentrations of light) and dark areas, improves transmission efficiency, and redirects light"

Filip,

I'm not sure what would be best. I'm not an expert in this area either. From what I have gathered though I think what we want is a low angular dispersion (less than 10 perent if possible). For 35mm lenses you could probably use their 50mm rimg-mounted diffusers. The other option would be to buy one of their rectangular sheets.

For me, since I am interested in using MF lenses, the 50mm will be too small an imaging surface. I'm going to have to purchase one of their larger sheets. What's great though is that these can be manufactured to anamorphically squeeze the image for you! No need for ANY lens!
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