I am struggling with the images from my new CP990. I primarily shoot photos of people which are all turning out with very heavy RED flesh tones. Doesn't seem to matter if outdoor or using flash indoor. The Camera has some nice manual overrides but I need the A-REC mode for all the members of my family to use and having to edit every shot with people is unthinkable. I've checked with other 990 owners and we've been exchanging photos, the RED saturation is not isolated to my camera. In fact some of the WEB examples show it as well but generally there are very few people in these pictures. I hope that Nikon is able to address this with a firmware update. Otherwise, I am not sure what to do. Any Suggestions?

-- Gary Fisk (gtfisk@hotmail.com), May 08, 2000

Answers

In all the current digicams the transfer function is incorrect. In addition to the obvious tonal range trouble this results hue-shifts. The scene colors will shift mainly towards the pure primaries (red, green and blue) and somewhat towards the pure secondaries (cyan, magenta and yellow). What are mostly affect are the so called cut colors (orange, violet etc) and hues with moderate or stronger saturation in the mid-tones and below.

The tranfer function is incorrect mainly because of two reasons: (1) it helps to hide the high noise in the shadows and (2) it is chosen so that both the users of uncalibrated Mac and uncalibrated PC see something in the images. In scanners we have the gamma control, when scanning with uncalibrated Mac the gamma is set to 1.8 (or more accurately to 1.72) and when scanning with uncalibrated PC the gamma is set to 2.5. This ensures that the scanned images appear correctly on these systems that have different system gamma. Digicam manufacturers have taken an approximation approach, they do not provide the gamma control so we get the tonal and hue problem.

If you had a good color input target such as the reflective Kodak Q-60 you could easily create an approximate calibration procedure that you can easily apply as an Action in Photoshop.

The correction is an approximation because the digicams amazingly alter their transfer function shot-by-shot (high-end digital camers do not do this). Even if the calibration can only be an approximation the improvement will be extraordinarily good. The target is only 29USD and you can find a very detailed instructions for creating such a calibration at my site: http://www.aim-dtp.net/aim/calibration/index.htm click the link ---Kodak Q-60 usage--- I will be glad to assist you in creating the calibration.

Timo Autiokari http://www.aim-dtp.net

-- Timo Autiokari (timothy@clinet.fi), May 09, 2000.

Wow, great site Timothy. A lot of good information. I plan on spending a couple of hours looking around and trying out your techniques.

John Peters ------------------------------------------- "See the light - B & W Digital Photography is here!" http://members.xoom.com/digipub/

-- John Peters (digipub51@hotmail.com), May 09, 2000.