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re: color neg drum scanning

Scanning negs with unknown colors, such as a sunset or
through a microscope, pose their own challenges, and the final color balance
often is up to the scanning operator to second guess the client.

We've had the best luck training color printing technicians, who are
accustomed to color corrections, to do scanning on negative film.

Creating successful color negative scans seem to pivot on being able to control for several factors:

1) The moving target presented by different orange masks from film to film,
2) Inconsistencies in the orange mask within one film type due to processing variances,
3) Characteristic curves that are radically different than those of transparency film (particularly at each end),
and perhaps most importantly -
4) Unknown colors

Three of these factors (1, 2, 4) relate directly to neutral gray balance. And the fourth (3) relates to black point/white point. Since a negative is an abstraction of a scene (as opposed to a literal rendition - as is a tranparency), we have an impossible situation if the person running the scanner is not the same person who shot the picture. The scanner operator can not view a negative and know what the intention of the photographer was. Where to set BP/WP? What to key on for neutral gray? There are interpretations to be made that the scanner operator is not equipped to make.

And so, here we are - mired in a world full of spectacularly sophisticated instruments being operated by intelligent humans - and still we can't get good drum scans from color negatives (unless the photographer happens to own the Tango himself - not likely!)

I think the problem is not one of specific settings, targets, etc. But rather a more general issue of approach and expectation. The tradition in the scanning business (service bureaus, printers) has been to supply a scan with optimal tonal range and neutral-balance color. That is an unrealistic, impossible standard when scanning color negs for the reasons stated above. I would suggest a different standard for color negs scans (i.e., high-end, fine-art quality scans). And that standard would not be to capture optimal tonal range / neutral-color balance. Rather, it would be to capture (in a 16-bit scan) ALL THE INFORMATION IN THE NEG regardless of optimal tonal range and neutral color balance. The scan, when viewed raw in Photoshop would, of course, look like dog droppings - flat and unsaturated. But if all the information is there, the image would be correctable with a few curves moves. And it works - I've done it. The challenge is to get the scanner operator to do that raw capture (with no USM!) and leave the interpretation to the photographer.

I had on off-line exchange with Bruce Fraser about this, and he suggested the following (... and Bruce, if you're reading this, tell me if I've got it right):

"tell the scanner operator to do as little as possible, and just grab the raw high-bit data from neg-to-pos conversion. That means not setting black and white points, not doing anything to gray balance, etc. There should probably be at least 20 levels of headroom at the shadow end and about 30 or more at the highlight end"

Perhaps high-end service bureaus running Tango's could offer color neg scans in this way. If a customer comes in and asks for a color neg scan "flat and unsaturated", that would convey the message.
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