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[filmscanners] Re: JPG sharpening [was: Color spaces for different purposes]

On Sun, 9 Jun 2002 10:52:22 -0230, you wrote:

>> There seems to be a widespread misconception here.  While
>> you are editing an image, it _does not have_ a format;
>> it isn't JPEG, or TIFF, or anything else.
>>  The image is stored on a file in JPEG or TIFF or whatever
>> format you choose, but it has no format during editing,
>> and so whether you edit a file opened from TIFF or JPEG makes
>> absolutely no difference while you are editing.  An image in an
>> editing program is just a mass of pixels.
>  I believe the "misconception" of always sharpening before JPEG comes from
>the common down-sampling.  That is, most images start out big before being
>down-sized for wwweb presentation ... and the usual advice is: ... down-size
>... sharpen (to remove the softening side-effects of down-sampling) ... and
>save as JPEG.

OK, I think I'm getting clear here.  So let me rephrase a bit.  When I
scan an image - into whatever file formet, I use TIFF out of Vuescan -
and then open it in PS, I can immediately see some sharpness loss
which I understand to be a result of the scan - scanner limitation,
etc.  One eventual step in my workflow is usually to try to restore
the image to something resembling the original slide, through the use
of as little sharpening or USM as possible.  If I try that on my
original file - before down-sampling - I have to use large USM values
to see any effect at all, or use "sharpen more" (I'm using PS Elements
at the moment).  Once I've resized for the web - typically to 800
pixels in long dimension, which I do using a bicubic resample and
changing the resolution, usually to about 600dpi from 2720 - the file
shrinks from its former +/-20MB to about 1.25MB and sharpening must be
done very cautiously in order to avoid halos and other artifacts.
When I resize for *print* I don't resample, I just change the
dimensions and leave the resolution the same.  It's in the down-sized
scan that I see the change in sharpening response.  

So, aside of asking for any observation regarding improving my
workflow - why is the sharpening so much more effective on the smaller
image? And am I losing something I'm not yet aware of?    I'm sure a
much more experienced eye can detect sharpening artifacts in my stuff,
but I've been relatively pleased with the results.  2 examples - feel
free to criticize:



But I'd like to understand more and get better results.

Thanks for all the explanations!  
Ken Durling

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