Scanner Replies
Scanner Replies
- Subject: Scanner Replies
- From: Michael Papet <email@hidden>
- Date: Wed, 17 Sep 2008 13:31:15 -0700 (PDT)
Mark said, "I put "raw" in quotation marks, because I don't believe the term raw means the same thing for this process as it does for cameras"
The term raw in a scanner is very different than a camera. Each scanner manufacturer has a different implementation of "raw". Yes, they are all whatever the claimed max bit-depth is, but how they get there varies. Marketing loves the term raw because it can be abused so easily.
Mark also said, "in the case of colour negs, the most "pristine" state in which they can be rendered is as a negative and linear.i.e. a negative colour image unreversed, the possible advantage being that I can "reverse" it to taste using some published techniques with Curves (usually in Lab mode)."
Mark, I used to work for a scanner manufacturer and directly with hardware/software Engineering. Scanning a negative is not ideal. There are so few CCD's with the sensitivity to pick up all of the data hiding in the negative and fewer still being used in a scanner. There are legions of other issues that Silverfast has sort of solved, Using negatives is really more for corner-cases and should be avoided. A good generalization is the best scans come from medium format or larger transparencies.
If you have more questions, please email me directly.
Eldon said, "Is it applying auto exposure to each new scan, or does
it always set a single exposure? If the former, I don't see how it's
possible to profile with any degree of certainty."
It's possible to profile with a great deal of precision regardless of exposure functions. This remark will inspire sudden thoughtless replies, but it is a simple point of fact, the sensor gets itself into a calibrated state before a slow scan. Preview, or quick scans rely on stored calibration states. Those are close enough in most instances as what happens after the capture as the image data passes through several processing black boxes before appearing on your monitor.
Michael
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