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Grain or noise?


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#1 John Atala

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Posted 27 March 2007 - 02:51 PM

Hello everybody,
So i just came back from a telecine of a short i shot with 7218 and 7205 S16. On the telecine session, i requested a bleach bypass semi look, simulating a partial bleach bypass. So, the guy contrasted and desaturated the image and we got a preety good result.
-but what about the grain?- the bleach grain.
one of the things that i dig the most of bleach that i achieved on previous tests with complete bleaching is the bleach-grain, that physical reference that only bleaching your negs gives you. So i asked the guy to take out a few dbs of noise redu and we got a overall apparent grain. Now, my question, is that grain video noise or just apparent grain from the s16 neg that the lack of the noise control shows you?

On my bleach tests, i noticed a greater apparent grain on the upper densities of the neg, and almost no apparent grain on the lower shadow areas, besides overall contrast. Does that follow?

if my observations are accurate, is there a way that i can on the DI create some sort of a matte on the shadow areas so that the apparent grain is shown just on the upper parts of the curve. On the other hand, this may be too time-consuming, i dont know.
I´m not sure if what i´m saying here is extremeley clear, but one thing is certain, i´m not happy with the overall grain. I´m afraid that what i seek is utopic, is it?

thanks for your time guys.
João Atala
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#2 Jon Kukla

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Posted 27 March 2007 - 05:58 PM

Yes, there should be more grain on the highlights than the shadows, assuming that you did the bleach bypass on the negative (or internegative). You're basically retaining a b/w image within your color image, so areas receiving more exposure will have more silver left in the negative, while the shadows will have little to no silver, and thus look much closer to an un-bypassed image. (Of course this is less apparent, since the shadows are by their nature dark.)

It is because of the extra density, particularly in the highlights, that it is advisable to underexpose the stock by around a stop - however, since the extra density is not equally spread across the exposure range, this is also why bleach bypass normally requires much more fill light/lower contrast ratios, since the shadows are now being underexposed without benefit of much extra density.

If you want grain and desaturation, but are worried about too much grain (esp a valid concern if shooting on S16), then you might want to look into bleach bypass AND pulling the stock a stop or so. It shouldn't affect your lighting too much, since in theory the two processes more or less cancel each other out as far as rating the stock. But it will enhance the desaturation while providing a slightly more graceful contrast (you can always add more in post) and slight compensation on the grain.
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#3 John Atala

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Posted 31 March 2007 - 06:58 PM

Yes, but that would be with the photochemical processing, but I´m talking about DI. I was wondering if there´s a way of achieving the bleach grain with a davinci telecine.

Thanks,
João.
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