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How Film Works


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#1 Brandon Yanofsky

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Posted 09 May 2007 - 03:45 PM

Hey guys. I just learned yesterday the composition of emultion in film. However, I am confused out of my mind exactly how one aspect of it works.

I was told that each color layer has two sublayers, one with larger grains that is faster and one with finer grains that is slower.

I don't understand how that would work. Since the larger, faster grains are hit with light before the slower grain, wouldn't they overexpose and when it is processed and transfered to a positive print, wouldn't it show as overexposed?

Obviously my logic is incorrect because it does not occur this way, so could someone please set me straight on how both fine and large grains can aid in the exposure of a scene and how it could technically work?

Thanks.
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#2 David Mullen ASC

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Posted 09 May 2007 - 04:22 PM

Well, you can imagine it this way: the fast grain layer is the basic image, correctly exposed, let's say, with a full range from bright to dark. So the fine-grained layer, since it is slower, basically is the same image but darker overall, with more detail in the highlights and less in the shadows.

So you figure that with development, the fast layer is providing shadow detail in the thin areas of the negative that the slow layer didn't capture... but the question is whether in the densest areas of the negative, it's all blocked-up by the big grains that got developed or whether it's sharing space with the information recorded in the highlights by the slower layer. Maybe since the slow layer is allowing dye clouds to form around the silver, it's creating color detail in the highlights even where on the fast layer, it's burned out?
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#3 John Sprung

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Posted 09 May 2007 - 05:26 PM

Film grains are essentially binary. They either get hit by enough photons to latensify, or they don't. The number of photons it takes to flip the crystal structure of a grain is the same, no matter how large or small the grain is. Therefore, given even exposure, the probability that a grain will expose is proportional to its area. Big grains are more likely to expose, small grains less.

If we were to make a film with a very wide distribution of grain sizes, there'd be some in the highlights that would be small enough to remain unexposed, and some in the shadows big enough that they would expose, and the film would be low in contrast. OTOH, if we could get all our grains pretty close to the same size, they'd all expose in bright areas, and none in dark areas, and the contrast would be very high.

Speed and contrast are determined by controlling the range of grain sizes.



-- J.S.
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#4 Brandon Yanofsky

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Posted 09 May 2007 - 05:58 PM

Well, you can imagine it this way: the fast grain layer is the basic image, correctly exposed, let's say, with a full range from bright to dark. So the fine-grained layer, since it is slower, basically is the same image but darker overall, with more detail in the highlights and less in the shadows.

So you figure that with development, the fast layer is providing shadow detail in the thin areas of the negative that the slow layer didn't capture... but the question is whether in the densest areas of the negative, it's all blocked-up by the big grains that got developed or whether it's sharing space with the information recorded in the highlights by the slower layer. Maybe since the slow layer is allowing dye clouds to form around the silver, it's creating color detail in the highlights even where on the fast layer, it's burned out?



I think I understand it now. I was confused that the grain was binary.

But what I think happens, correct me if I'm wrong, is that by allowing two layers, the fast will be exposed pretty much in whatever condition, so you get detail in shadow. If the slow is not used, it will be washed away, but if there are some overexposed areas on the fast layer, the fast grain in that area will already be "turned on" and will continue to the slow layer. When the die is created, it will not be as black (on the negative print) because the slow film will not have been completely exposed, whereas if it was just fast grain, it would all be overexposed and black (again, on the negative).

Hopefully that makes sense and you can decifer it. God, who thought film was so complicated.
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#5 Jonathan Bowerbank

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Posted 09 May 2007 - 09:28 PM

God, who thought film was so complicated.


Thomas Alva Edison
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#6 James Steven Beverly

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Posted 09 May 2007 - 11:49 PM

Why do ya think all these film schools are goin' to video. <_<
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#7 John Sprung

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Posted 10 May 2007 - 12:31 PM

Thomas Alva Edison

George Eastman, actually. He did the complicated part with the halide chemistry and sticking it to celluloid. Edison had his staff work on ways of shooting and presenting a rapid sequence of still images to produce the illusion of motion. That was utterly impractical with glass plate negatives, but once Eastman coated a photographic emulsion on flexible film that could be rolled up, all the pieces were available.


-- J.S.
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#8 Leo Anthony Vale

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Posted 10 May 2007 - 02:05 PM

George Eastman, actually. He did the complicated part with the halide chemistry and sticking it to celluloid. Edison had his staff work on ways of shooting and presenting a rapid sequence of still images to produce the illusion of motion. That was utterly impractical with glass plate negatives, but once Eastman coated a photographic emulsion on flexible film that could be rolled up, all the pieces were available.
-- J.S.


Kodacentrism!
Nicephore Niepce and Henry Fox Talbot independenly came up with photo emulsions. With Niece taking the first known photograph decades before Eastman was born.
Richard Leach Maddox invented the dry plate in 1871. The Eastman Dry Plate Co. opened in 1880.
Eastman brings out roll film in 1888, which is paper. He puts it on a celluloid base in 1889.
However celluloid film was invented by Hannibal Goodwin in 1887.

Let's not forget that the Lumieres invented the sprocket hole and that Edison's moving picture camera patent
bears a suspicious simularity to the Lumiere patent.
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#9 John Sprung

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Posted 11 May 2007 - 07:36 PM

Kodacentrism!
Nicephore Niepce and Henry Fox Talbot independenly came up with photo emulsions. With Niece taking the first known photograph decades before Eastman was born.
Richard Leach Maddox invented the dry plate in 1871. The Eastman Dry Plate Co. opened in 1880.
Eastman brings out roll film in 1888, which is paper. He puts it on a celluloid base in 1889.
However celluloid film was invented by Hannibal Goodwin in 1887.

Let's not forget that the Lumieres invented the sprocket hole and that Edison's moving picture camera patent
bears a suspicious simularity to the Lumiere patent.

All very true -- My point was that Edison simply bought film from Eastman, he didn't mess with the emulsion making himself -- or in house at his company. Edison may not have invented OEM outsourcing, but he certainly was a big early adopter. ;-)


-- J.S.
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#10 Leo Anthony Vale

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Posted 12 May 2007 - 01:07 PM

Edison may not have invented OEM outsourcing, but he certainly was a big early adopter. ;-)
-- J.S.


Particularly when one consider's he plagarised a foreign patent.
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