Tony,
At 09:11 26/01/03, you wrote:
>I performed these exact experiments about a year ago when the DOF issues
>were being discussed at length. My tests were done on a Kodachome 200 slide
>which I specificaly used because of the ease with which I could focus on the
>grain.
>
>My own personal tests made it evident that anything much outside of -5 and
>+10 from critial focus (this is using Nikonscan's focus units) started to
>show unacceptable softening. That to me does not give much leeway in
>focusing on a pice of film to get the image sharp across the whole length of
>the film. Og course other peopple may not be as fussy with sharpness across
>a scan but -5 and +10 are my own personal comfort levels. As a result all my
>film is now left uncut and stored in negative sheets so it remains perfectly
>flat for scanning. Any probematic pieces of film go in a glass slide mount
>with anti-newton glass.
Thank you! It seems that the LS4000 is much the same as the LS2000 in
optical DOF and in calibration of arbitrary focus units, since my critical
DOF was +/-6 units. i.e. your range total is 15 compared with my 12 - well
within experimental error! As I said before I found I could get usable
images (not grain sharp but image-sharp, enough to be undetectable) over
double this range.
Thanks again that was useful,
Julian
Julian
Canberra, Australia
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