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base fog density...


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#1 pushpa

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Posted 07 August 2008 - 07:40 AM

hello to everyone who r reading this lines...

in a book i came across something like base fog density while reading about push processing...what exactly is base fog density... :huh:

cheers :P
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#2 Brian Pritchard

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Posted 12 August 2008 - 04:03 PM

hello to everyone who r reading this lines...

in a book i came across something like base fog density while reading about push processing...what exactly is base fog density... :huh:

cheers :P

Base fog density is the densitometer reading for unexposed film after processing. In the case of colour film it would be Red, Green and Blue densities and for Black and White film a visual density. The fog level will increase as film gets older and also it will increase with push processing. The higher the base fog level the lower the maximum black you would get in a print. Labs will often test samples of old batches of film stock by processing a piece of unexposed film and reading the base fog density. If it has been badly stored or very old then the fog level will be high and the film should not be used.

Brian
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#3 Tony Brown

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Posted 24 August 2008 - 03:50 AM

Base fog density is the densitometer reading for unexposed film after processing. In the case of colour film it would be Red, Green and Blue densities and for Black and White film a visual density. The fog level will increase as film gets older and also it will increase with push processing. The higher the base fog level the lower the maximum black you would get in a print. Labs will often test samples of old batches of film stock by processing a piece of unexposed film and reading the base fog density. If it has been badly stored or very old then the fog level will be high and the film should not be used.

Brian


Never understood those graphs. I just frown and go "hmmmmm.....interesting"
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#4 Charles MacDonald

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Posted 29 September 2008 - 09:51 PM

Never understood those graphs. I just frown and go "hmmmmm.....interesting"

If you hold the negative up to the light, the area that is NOT exposed, is more or less clear, (or Orange on colour neg). AS the film gets older, or is poorly stored, that area has more and more density. NO film is "perfectly clear" {richard Nixon home movies excepted} and so one can measure the base fog.

You might think of it as the more base fog, the less "room" there is for Highlight density, or just as a test to see how much wear and tear the film has gone through.

The curves start to make more sense the more you play with them.
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#5 Simon Wyss

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Posted 26 October 2008 - 04:54 AM

If you hold the negative up to the light, the area that is NOT exposed, is more or less clear, (or Orange on colour neg). AS the film gets older, or is poorly stored, that area has more and more density.

Hello, only want to clarify this little detail: As raw film gets older or is poorly stored, base fog density can increase, measurable after processing.
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