[HDR-photo] color casts

[Bernhard Vogl]

Hello John,

Without seeing a a sample of your specific problem, i can only assume some standard sources of problems, mostly already covered in the previous answers:

- Wrong WB: There is AFAIK no "correct" WB for MDR(HDR) shots in a "photographic" meaning. Technically, it would be the most correct approach to capture the images with "sunny" WB to have full color response and adapt WB later in the HDR image. You can modify the WB with some of the available HDR software packages. E.g. in HDRShop you can define a region and auto-WB the HDR based on the selection.

As long as you have a substantial amount of sunny areas in the image, i'd prefer to shoot with "sunny" WB - otherwise the bright areas look very oversaturated. However - shady areas will therefore have a blueish appearance. This can also be seen in LDR images but it is in the nature of the extended dynamic range that the effect will increase in HDR shots.
There are several approaches to reduce such "oversaturation" and mimic the eye's reception of HDR sceneries. One of the best known operators is the "photoreceptor" TMO (http://dativ.at/logmap/  ...scroll down for image example).

In case you're shooting without direct sun (shady areas,evening/night scenes, indoor with artifical light and no window with sun lit outside) i think, it is also valid to use "shady" or "tungsten" WB to avoid the color cast.

- Wrong EV spacing: Although common best practice is to use 2 EV, you may need another setting for your shooting. E.g. if the overlapping shots are too many EV apart, HDR merging may include image regions with oversaturated sensors, resulting in color aberrations

Best regards
Bernhard