[filmscanners] Re: Scanning a foggy image

["Tony Terlecki" <ajt@mrps.demon.co.uk>]

On Sun, Aug 04, 2002 at 08:43:07PM -0400, Brian wrote:
>     OK, let me ask a question. I have a rather nice slide of a boat dock
> with some small boats moored which I took up in Maine. There was a slight
> fog/mist in the air when I took the shot. A print made from the slide
> captures the foggy nature of the composition nicely. However, when I scan it
> (Nikon Coolscan 4000) using ViewScan, the scanner/software seems to
> interpret the fog as noise(??) and produces a scan with more clarity than
> the original image has.
>     My question is, how do you scan slides or negatives which are somewhat
> soft with fog or mist and retain the look of the original scene? Failing a
> scanning solution, is there a tweak I can do in Photoshop to get the
> appearance back? I've been doing this for about a year so I'm not real
> experienced by I have learned quite a bit reading the emails on this group.
>

Usually fog presents a very low contrast image. Most scanning packages will
try and set black and white points at the edges of the scanned tonal values.
If the image is low contrast this has the effect of expanding the contrast
range and so will reduce the fog effect.

In Photoshop a typical technique is to use the Levels tool and both raise
the output blackpoint and lower the output whitepoint. You can do the same
thing, but with more control, using the Curves tool.

--
Tony Terlecki
ajt@mrps.demon.co.uk
Running Debian/GNU 3.0 Linux

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