Although the discussion has become quite heated, the exchanges are increasing my
knowledge level of scanning and therefore the group scan is meeting one of its goals,
to learn.
There is a problem with the JPG compression. I was not aware that JPG compression
might be HIGHER on one image than another and show artifacts in one type of image that
did not show in another. The Level 6 was choosen because on my system the Halloween
and bug catcher slides didn't show JPG artifacts at 100%. I do see them clearly with
the SS4000 scans and am trying to access what would be a viable alternative as 27
megabyte scans are not an option to post up. :)
Ed has explained a probably solution to the difference in "gamma" of the images.
Unless there has been operator error, the Gamma setting has been consistant between
the scanners, however the computation for exposure between the difference scanners
must obviously be different. This alone, I believe would account for the
darkness/lightness issue.
Again going to exposure this is the only reason I can think of the black point on the
images being different for the SS4000 than the elite, or the cannon. Since a black
point in vuescan cannot be set to a specific RGB value and the required setting is 0,
there can be no other explanation for a variance in the placement of this data without
VueScan making an exposure change from device to device.
So, perhaps Ed can shed further light and it can be decided if these are fatal flaws.
alan
>> (a) The gamma and black point of the Polaroid (Halloween pic) are set
>> lower than with the others (and the highlights clipped) by overexposure,
>> and the Elite is set higher than the Canon and Acer. As with *any* scanner
>>
>> this exposes CCD noise in the Polaroid which would not normally be seen,
>> and conceals noise in the Elite which would be. I suggest you try
>> normalising them by adjusting Levels in PS. Doing so loses the noise
>> without losing shadow detail. The noise ranking then changes to Pol4000
>> (least noise), Elite, Canon, Acer (most).
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