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[OM] Re: scanning print negatives and scanner exposure inconsistencies

Subject: [OM] Re: scanning print negatives and scanner exposure inconsistencies
From: Moose <olymoose@xxxxxxxxxxxx>
Date: Fri, 28 May 2004 14:11:50 -0700
Couldn't stay away, Boris?

alienspecimen@xxxxxxxxxx wrote:

> So...Istn't the dynamic range to digital as the exposure latitude to film?

>  In this case, I dont understand why the slide has greater "dynamic 
> range".Boris
Two things being mixed together here. The range of densities of the film 
itself is less for color neg film than slide film. It has to be, since 
slide film can go completely clear and almost completely opaque, while 
neg film can only go from almost opaque to the density of the orange 
mask. Thus slide film requires a greater Dmax on the scanner to capture 
all the luminance. This is not an issue with recent film scanners.

The second part is an issue of mapping. Each light level that hits the 
emulsion results in a specific density in the developed film. The total 
range of film densities on  film 'map' a limited range of incoming 
brightness which is often less than the total range of brightness in the 
subject. Thus some of the highest and/or lowest parts of the actual 
range of brightness that hits the film are lost (or compressed) into the 
single brightest tone and darkest tone the film can produce. The 
difference between slide and neg film is the mapping. Slide film maps a 
narrower range of subject brightness than neg into a broader range of 
film density than neg. Another way to say it is that the range of 
subject brightness is compressed into a smaller range of film density on 
neg film and the compression is such that a greater range of incoming 
brightness can be recorded than for slide film.

There are advantages and disadvantages to both.

>This hath not offended the king.
King? What King? I don't see any Kings around here! No Elvis in Berkeley?


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