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filmscanners: Silverfast lamp lightness option



Reading Ian lyons very helpful tutorial "Silverfast 5 and the Polaroid
SS4000 : Part 1 - Basic steps to IT-8 calibration", I found he used a value
of 10 for lamp lightness. He noted that this allowed him to maximise shadow
detail.

Sounds good to me, but how do I know what value would be good for my
(mechanically) similar Artixscan 4000 ?

After a little thought I came up with the following technique:

I used IT-8 slide with the HDR option. I made an initial scan and used PS to
check the RGB values in the grey scale area for rectangles "0" and "23"
which I think should be pure white and pure black respectively.
I found the white was well short of 255 in every channel. So I tried
progressively higher values in lamp control until it became almost
completely 255 in every channel. I then backed the lamp control off until
the values were generally 255/254 in every channel. This by my reckoning
maximised the bandwidth as the black was still showing RGB 0/1 or sometimes
2. I then recalibrated using the IT8 slide. I checked a before and after
scan nd I do not appear to have introduced loads of noise.

My final value was 24 where as Ian ended up at 10.

Does my technique of arriving at the final lamp setting make sense ?

Can anyone suggest anything better ?

Any nasty flaws ?

Steve




 




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