EM-5: Confused by Auto White-Balance results

Started Feb 12, 2013 | Discussions thread
Paul De Bra
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Auto White Balance is magic, and magic can go wrong...
In reply to Timur Born, Feb 12, 2013

All camera makers struggle with the auto white balance feature. I must say that in general I'm happier with the AWB on my E-M5 than I was on the Canon cameras I had before.

AWB tries to guess what the lighting was in a scene. It really has nothing to go on. An image contains objects of different colors, and the colors look different depending on the lighting of the scene. AWB tries to "neutralize" an overall color cast that could be caused by colored lighting such as tungsten lights. Essentially AWB deviates from a standard daylight when it discovers there is more red than expected (tungsten lights) or more blue than expected (cloudy weather, shadow on a sunny day, or light at dawn or dusk). When you take a picture containing almost all blue AWB will tone down the blue (by using a high color temperature) and it will not look right. And when you take a picture containing almost all red AWB will also tond that down (by using a low color temperature). AWB wants the "overall" color of a scene to be closer to a neutral grey.

There is only one situation in which AWB can do something that is at least partly sensible: when the flash is used. Assuming most of the light is coming from the flash the camera knows what color the light of the flash is. So even when you do not use the flash-WB preset the camera has a good idea about the lighting of the scene. In all other cases it's an educated guess, on the scene's overall color or the color of some larger parts of the scene. I am actually amazed that AWB on any camera does as well as it does.

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Slowly learning to use the Olympus OM-D E-M5.
Public pictures at http://debra.zenfolio.com/.

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Fujifilm FinePix F200EXR Olympus OM-D E-M5 Olympus M.Zuiko Digital ED 9-18mm 1:4.0-5.6 Panasonic Lumix G 20mm F1.7 ASPH Olympus M.Zuiko Digital ED 75-300mm 1:4.8-6.7 +4 more
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