scanner as densitometer

kaiyen said:

This has been asked a few times on photo.net.

The basic answer is that it's possible to build a curve, but only if you can first get some kind of known value as a reference point. this is difficult with most software because of auto exposure, levels, etc. With something like VueScan, at least you can lock in exposure, but it's still difficult to get a good starting point. I've read that it's somewhat easy to build a curve relative to some quasi-arbitrarily fixed point, but it's hard to find a "real" fixed point.

Pat Gainer posted at the bottom of this thread about making an assumption about pure white being zero density on the screen. That allows for some calculations, but is again symptomatic of the need to find some kind of fixed point to start off with.

This thread is another interesting discussion on the topic.

I am in the process of trying to figure out film speed and development times with my Nikon Coolscan IV myself.

allan

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rbarker said:

Another option is the densitometer mode of the enlarging meters from RH Designs, that measures relative density from the image projected by your enlarger. Whether that feature is sufficient for your densitometer odometer (YMMV) is an exercise left to the reader, of course.

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