high altitude color
Seems to me that the film I shoot at high altitudes (10,000 feet plus) give me more trouble in trying to get the color right than the film I shoot much lower. I just processed a bunch of film at shot at close to sea level and it scanned like a dream. Just got back from high in the sierra's and I just can't get the color right. Any ideas?
I'm shooting velvia and ektar.
At higher altitudes there is more light from the shorter wave part of the spectrum. This means more blue, violet and ultra-violet. In other words the color temperature of the light is higher than at sealevel. Average color temperature at sealevel is ~5600K while at higher altitudes it can be 10,000K or higher.
Try using a Wratten 1A (skylight) filter first and if this does not provide enough correction then try a Wratten 2A filter. There is a similar problem on overcast days. On gray, dreary days I use a Color Correcting filter such as a CC 05R (red) or CC 05M (magenta) filter to warm things up a bit. You will have to do some experimenting as to which filter provides the best results for you. Here is a list of the Wratten filters. http://en.wikipedia.org/wiki/Wratten_number
Each color film has its own spectral response. Perhaps a different film might work better. Some emphasize cooler tones while others warmer ones.
The color temperature of daylight is effected by several factors such a the position of the sun. Thus the color temperature is highest just before sunrise. I would suggest that anyone who is a serious color photographer read up on this subject.