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Old February 13th, 2006, 12:20 AM   #46
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Wow, I have POC 30 and the grain is huge when compared with my GG (???)
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Last edited by Jim Lafferty; February 13th, 2006 at 08:35 AM.
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Old February 13th, 2006, 12:28 AM   #47
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Keith,

You may want to try checking sandwich bag materials (or veggies or some such). They offer more light transmission than the POC materials. Just check their diffusion because if the diffusion is not circular your bokeh will not be as pretty.

The most beautiful bokeh I have got is from a double layer Tx96.6% veggie bag (perpendicular so diffusion is circular). But transmission drops to 93% due to the double layer. (which isn't actually too bad)

Dennis, I am glad you are converted. Resistance is futile.
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Old February 13th, 2006, 12:59 AM   #48
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Jim, I'm pretty sure the 30 has too much diffusion/light loss. The 20 has very good diffusion (better than anything I've made), but I think 15 (which I don't have yet) is the likely ideal.

Comparing the many GG's that I've made, the finer ones simply did not diffuse enough....some liked the look, but many pointed out wierd bokeh. The grain of my latest favourite GG matches the LSD 20 pretty closely, but there's no question that the 20 has more controlled diffusion...and at least .7 f/stops better light gain.

Forget static with these....the grain is way too big. It must be moved...and quickly. I am testing some spinnners with AR coatings and 1 micron surface relief. Should be interesting to see how they compare with the POC samples.
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Old February 13th, 2006, 08:54 AM   #49
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Hmm... I've been thinking 60 or greater POC parts would be better suited for the GG as their grain is less visible, but of course the uphill battle with them is severe light loss. To a point, I'm not that hung up on what the bokeh looks like, quite frankly, nearly so much as I am getting grain as supressed as possible while losing as little light as possible.
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Old February 13th, 2006, 09:11 AM   #50
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I've got an 80 degree POC diffusing film sample. Way too much light loss, forget it.
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Old February 13th, 2006, 09:15 AM   #51
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You're right Jim, it's somewhat subjective. I can get zero grain with 1 f/stop light loss, super sharp etc. with my less diffuse GGs. Problem is when I post something with that GG, I get the "looks like a promist filter" comments. You won't see it in darker footage as much as light stuff, particularly specular highlights.

I'm convinced so far that the 20 degree POC LSD (and more likely the 15) has got the "right" amount of diffusion. Better than anything I've seen yet. It also corresponds both in terms of static grain and diffusion levels to my GG that has produced the greatest positive feedback. The upside is the the POC does it with .7 F/stops relatively less light loss.
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Old February 13th, 2006, 09:57 AM   #52
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Quote:
Originally Posted by Jim Lafferty
Hmm... I've been thinking 60 or greater POC parts would be better suited for the GG as their grain is less visible, but of course the uphill battle with them is severe light loss. To a point, I'm not that hung up on what the bokeh looks like, quite frankly, nearly so much as I am getting grain as supressed as possible while losing as little light as possible.
Jim, if you don't care for bokeh, use a sandwich/veggies/home depot bag. It will give you small grain and the best light loss. Much better than the POC materials. You may even get lucky and find one with circular diffusion and then your bokeh will look great as well.
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Old February 13th, 2006, 10:13 AM   #53
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Here is a compiled table of all materials tested so far:

Beattie Intenscreen
Diffusion angle:~15° Transmission: 97%

Veggies Bag
Diffusion angle:~5x20° Transmission: 96.6%

Thick pouch + Coating on one side
Diffusion angle:~5-7° Transmission: 96.2%

Sandwich bag 2
Diffusion angle:~5x25° Transmission: 95.3%

Thick pouch
Diffusion angle:~15° Transmission: 95.1%

POC LSD5PC10
Diffusion angle:5° Transmission: 94.7%

Sandwich bag 1
Diffusion angle:~5x25° Transmission: 93.5%

Office Depot Magic Tape
Diffusion angle:~15° Transmission: 93.5%

POC LSD20PC10
Diffusion angle: 20° Transmission: 93%

POC LSD30PC10
Difussion angle: 30° Transmission: 91%

Redrock M1 GG
Diffusion angle: ? Transmission: 81.3%

Last edited by Alain Bellon; February 13th, 2006 at 11:09 AM.
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Old February 13th, 2006, 10:14 AM   #54
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"Sandwich bag"

Alain, could post some pictures of the wonderful sandwich, veggies etc bags...I'm looking for one here in Norway....but can't spot any of these...Thanks.

I also wonder which kind of GG the Letus35 Flip uses....
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Old February 13th, 2006, 10:44 AM   #55
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My guess would be hand ground or pre-ground, 1500 grit glass.
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Old February 13th, 2006, 10:55 AM   #56
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I beleive it to be 600 grit, which is an excellent choice for a vibrating adapter.
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Old February 13th, 2006, 11:03 AM   #57
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Letus 35 improvement

So replacing the GG grit by a Beattie Intenscreen should per def bring huge improvements to the picture. Right ?
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Old February 13th, 2006, 11:11 AM   #58
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http://www.dvinfo.net/conf/showthread.php?t=58599

Ben's thread on same subject.
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Old February 13th, 2006, 11:25 AM   #59
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Changing the GG to one of these holographic diffusers (POC, Beattie, Bag) will reduce the lightloss, but it may not make your picture better.

For example, here are some quick images of the bokeh produced by a couple materials. They are taken with a 50mm lens with the focus ring pulled all the way towards the near end (excuse the dirt, but was a really quick test swaping the screens):

Thick material (~7°, 95.1%):

http://mentemagica.com/35mmAdapter/B...-Thick1-sm.jpg

Thick material coated (~15°, 96.2%):

http://mentemagica.com/35mmAdapter/B...Coated1-sm.jpg

Sandwich double layer perpendicular (~15°, 91%)

http://mentemagica.com/35mmAdapter/B...chPerp1-sm.jpg

Andy Gordon posted an image from the Beattie bokeh (~15°, 97%):

http://imagedump.filefactory.com/full.php?id=2514

As you can see, light transmission is not the only factor here. The Beattie looks very similar to my thick coated material: Bright hotspot right at the light point and then a fuzzy haze.

But the sandwich bag double layer (unfortunately the lowest transmission of the 3), gives the "nice" circular disks some of use like to see.

At this point I really do not know if there is a way around this. Any thoughts?
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Old February 15th, 2006, 07:33 AM   #60
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Alain,
Tried your software light transmission test on the SG35's GG material, and it reports 97 - 99% depending on where i place the boxes. Im not sure if this is correct or im doing something wrong with the software.
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