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[OM] Re: More Fuel on the Film/Digital Dialogue

Subject: [OM] Re: More Fuel on the Film/Digital Dialogue
From: Joe Gwinn <joegwinn@xxxxxxxxxxx>
Date: Sun, 24 Jul 2005 22:29:44 -0400
At 3:47 AM +0200 7/25/05, Listar wrote:
>Date: Sat, 23 Jul 2005 23:05:07 -0700
>From: Moose <olymoose@xxxxxxxxxxxxxxx>
>Subject: [OM] Re: More Fuel on the Film/Digital Dialogue
>
>R.Jackson wrote:
>
>>This is very interesting. There seems to be an overall effect of the 
>>blending that influences saturation and masks some of the plastic-y 
>>feeling that video sensors often have.
>>
>Noise affects much more than just "graininess". AG just commented on the
>effect of iso on the skin tones in his work, because the noise at
>different isos made subtle changes in color balance. That is probably
>part of the reason it is so difficult to pin down the difference between
>digital and film, the difference in amount and structure of noise
>effects much more than one might imagine.
>
>It's very interesting to move the transparency slider back and forth on
>the grain layer and watch what happens to the image.

One big difference is that most of the digital noise is added to the 
image, while with film, a major part of the the noise is 
multiplicative.  Actually, it's more complex than that, as over and 
under exposure causes increased grain.

Additive:  To each pixel add a small random number.

Multiplicative:  Multiply each pixel by a number that randomly varies 
around 1.00.

Real systems do both.

Joe Gwinn

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