[filmscanners] Eyedroppers in Curves in Nikon Scan

["Jerry Lodriguss" <jml@astropix.com>]

Could anyone explain the behavior of the gray eyedropper in the Curves Tool 
in Nikon Scan v3.1.2?

If I use Auto Levels to automatically set a black and white, and then use 
the gray eyedropper to click on a gray card I have in a test image, the 
pixel values in the gray card, which read 104,117,103 are re-mapped to 
111,119,130 instead of 128,128,128 as specified in the preferences. (I have 
the sample point set to 5x5 so it's not a weird single pixel).

Here is the behavior as I see it:

·       Clicking the auto levels first correctly sets black and white 
points. Then clicking a gray point does not correctly set a neutral gray.

·       Clicking the individual black and white point eyedroppers on the 
darkest and lightest pixels in the image correctly sets black and white 
points, but then clicking the gray point eyedropper in the gray card does 
not correctly set a gray point.

·       Re-setting auto levels and using the gray point eyedropper first 
correctly sets a gray point, but these neutral gray pixel values are 
changed, and do not remain neutral if black and white points are set after 
a gray point is set.

This is not the behavior that Photoshop exhibits. If one sets the black and 
white points in curves with Auto, and then clicks the gray point eyedropper 
on the gray card in the image, the black and white points stay locked, and 
the gray gets re-mapped to 128,128,128, or whatever you have specified in 
the preferences in the Curve's options.  This is the behavior one would 
expect, and desire.

So what is the deal with Nikon Scan?

Thanks,

Jerry



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