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Dynamic range is not well defined. It is very important, but there is no formal specification to define it numerically, and it can be about any value that the advertising department wants to call it.
Specs for inexpensive scanners often confuse reality, stating theoretical maximum
instead of measured results.
Imacon is one the of best brands.

4.0 is logarithmic, and 4.0 is 10 times greater range than 3.0.

4.0 is not an absolute limit, because it is the mathematical logarithm of
the density range, and the logarithm is not limited. Give the
formula more bits, and get a larger log.

It is a practical limit, the range of film does not exceed 4.0 in
reality. Usually the spec concerns density range, DMin to DMax, and
usually in a very optimistic way. Often the theoretical maximum for the
number of bits is computed, and used, and the scanner itself is usually not
any factor at all in that number... only the number of bits in the computation.

The absolute theoretical maximum of the logarithm from 14 bits is 4.2, if
DMin were assumed to be zero, and if it were assumed there was no
electronic noise to detract from measured results. This 4.2 range is very far down into the noise level of lesser scanners.

See http://www.scantips.com/basics14.html , at the table towards the
bottom, and the page in general covers this topic.

Wayne
fulton@scantips.com
http://www.scantips.com "A few scanning tips"

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