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Old July 31st, 2006, 03:24 AM   #1
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Light loss versus nice bokeh?

Am I right if I assume that:

The bright screen should be designed to work with all lenses down to f/5.6 and it will have the Precision Matte random micro lens construction with elements of varying size and sensitivity.

The bokeh screen should have finer micro lenses than the bright screen along with a steeper parabola of focus to make the out of focus areas appear more filmic, identified by light discs with sharp edges in OOF areas.
However, this screen should not be recommended for slower lenses because it wouldnīt be that bright. The difference in illumination will be roughly one f-stop.

Thanks in advance,
T
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Old July 31st, 2006, 08:57 AM   #2
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I would rephrase that problem:
1. My opinion is that bokeh isn't characteristic of screening glass but it is characteristic of photolens. I explained it here: http://www.dvinfo.net/conf/showpost....4&postcount=23 .
2. Your assumption is only right by next to cases:
a) if You reduce my 1-st point to bokeh problem
b) if You're using traditional screening system - projection on groundglass.
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Old July 31st, 2006, 10:04 AM   #3
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Sure..

Iīm speaking little bit in Canonīs manufacturing/marketing terms here.
By my research Canon manufactures at least two types of clear focusing screens for modern DSLRs. One of witch is described as brighter, standard screen and another with finer micro lenses along with a steeper parabola of focus designed for precise manual focusing with brighter lens.
My assumption was based on that information.

By all means those screens are traditional modern focusing screens in general.

Regs,
T
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Old July 31st, 2006, 03:38 PM   #4
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oh, i'm sorry

when i posted earlier i just skipped words "micro lens" reading Your intropost. Microlens arrays are step further from groundglass and not so traditional. I'm curios now :). Have You something specific(microlens array as product) in Your mind?
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Old August 1st, 2006, 02:01 AM   #5
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Yes, Canon is making those

As far as I know Canon has those two focusing screens that utilise microlens.
>The standard and brighter one
>And the super precision one

I´m going to visit local Canon facility in next few days to verify if those screens are any good.

Canon sells those for $/€35 each.

Regs,
T

Last edited by Toenis Liivamaegi; August 1st, 2006 at 03:25 PM.
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Old August 1st, 2006, 04:55 PM   #6
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i tought sensor will take picture directly ...? Or is it for presenting image via VF
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Old August 2nd, 2006, 01:34 AM   #7
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Yes

Itīs for for presenting image via VF.
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Old August 2nd, 2006, 02:32 AM   #8
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You've seen both Canon versions? Asking because I actually have not seen any microlens array in photocameras. But those which using ordinary GG are grainy as hell.
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Old August 2nd, 2006, 03:11 AM   #9
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Just not jet

I`m getting the brighter one later today but I´m afraid that we must wait another 10days to get the one with super fine microlens as there wasn`t any in stock.
Good thing is that I can already design a screen holder for those screens and see how they work with my unique leaf spring biaxial oscillator.
Therefore I can compare a Beattie, Nikon and those made by Canon.

For now I know that our HVX will need an achromat to get close enough but I assume that a sub $100 achromat also manufactured by Canon will be enough, we`ll see. If nothing else we can perform lab tests with 8Mpix DSLR with real macro lens attached.

Regs,
T
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Old August 2nd, 2006, 04:54 AM   #10
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Basicly grain is seen right from photocamera VF. Just for saving time.
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Old August 2nd, 2006, 06:20 AM   #11
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Frank, it`s well known that focusing screens from SLR cameras have at least some degree of visible grain but that`s not my main concern at all beacause my design blurrs the grain with oscillating motion therefore reducing grain noise visible to camcorder. One limitation of that design is that with higher and higher shutter speeds the grain becomes visible again as the oscillating motion isn`t fast enough.

I`ve had many (D)SLR cameras and their viewfinders are sometimes like night and day. I currently own three Canon SLR cameras and their viewfinders are quite grain free.
To illustrate that look at traditional ground glass and laser matte one and compare it with the earliest microlens focusing screen that Canon introduced already in 1971.
Not to mention that spacing between ring peaks on a Fresnel lens on that screen were only 0.03mm resulting in much sharper (viewfinder) image.

I quess I`m not gonna waste my time.

Regs,
T
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Old August 2nd, 2006, 07:00 AM   #12
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rather Your experiment will be very interresting - no doubt. As i said earlier, i never seen microlens arrays used in such application. I'll wait rather from such experimentations good news like breaking some main physical trade-off law:
t-stop vs hotspot
grain vs t-stop
etc

btw. what is the size of those plates?
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Old August 2nd, 2006, 07:18 AM   #13
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Those sceens are about 36x24mm in size covering full 35mm still photography frame thus giving even shallower depth of field than normal cine lenses for the same t-stop.
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Old August 2nd, 2006, 07:54 AM   #14
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All products are available here:

Canon Focusing Screen Ee-A
Canon Focusing Screen Ee-D
Canon Focusing Screen Ee-S
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Old August 9th, 2006, 01:01 PM   #15
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But don't these have focusing circles? We've discussed the Ee-A and Ee-S over on DVXuser and both were confirmed as having focusing circles. You'd have to zoom in beyond that in order to get a usable image, and at that point you're negating the 35mm FOV, aren't you? Just wondering. I'd love to see the results of these tests.
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