On Wed, 03 May 2000 18:10:46 -0500, Chris Huff
<chr### [at] yahoocom> wrote:

>> A better way to increase contrast would be to apply the
>> filter as I've specified it, then apply an S-curve-shaped correction
>> to stretch the midrange.
>
>I have been thinking about this...is there a "standard" curve used for 
>this, or should I just come up with something?

For what it's worth, here is one example of an S-curve:

    Output = 0.5-(cos(Input*pi)/2)

For this to work, both input and output need to be constrained between
0 and 1. It should work with other ranges of values with appropriate
scaling. The angular unit is expressed in radians, in this example.

This generates an S-Curve, but I'm not sure of an easy way to add
additional parameters and make it more flexible, without losing the
"S" shape.

This curve is also very similar to a generic representation of the
response curve of photgraphic film. It would need some modification to
work as a film response emulator, a subject I raised earlier. The
input range would need to accept those unclipped float values, and the
ouptput would need to be constrained to a range suitable for the
output file format. I'm not yet sure how to add the extra parameters
to do this properly.

Later,
Glen Berry

Later,
Glen Berry

( Remove the "7" from 7no### [at] ezwvcom to email me. )

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