RAW vs White balance

Started Nov 20, 2006 | Discussions thread
philzucker
philzucker Veteran Member • Posts: 8,710
Real world test

Here a quick and dirty "real world" test of the influence of WB settings for color rendition in RAW.

The setup: Ds on a tripod. DA40, manual focus, ISO 200, manual exposure 1/3s, f4. Light: Three candles in an otherwise dark room. No other light sources. I took four pictures with WB set to 1) Auto, 2) Sunshine, 3) Tungsten and 4) Shadows and then opened the pics in ACR 3.6 (PS CS2). Everything "auto" disabled of course, default values were used. Here how it looks unprocessed (just resized) at Auto WB:

Camera WB reported in ACR was 5500 both for Auto WB (!) and Daylight settings, 3050 for Tungsten and 6550 for Shadow

I then developed all pics to the same WB of 5500 Kelvin and compared those four pics carefully. It was not easy to discern any differences at all to the naked eye - but switching between them one could detect minuscule ones; I detected some differences in the blue channels, especially while comparing the instances with Tungsten and Shadow WB with each other; but even here nothing really strong. Here the four pictures:

(For those who want to make their own comparisons here a larger version without text captions: http://www.pbase.com/phsan/image/70665021/original )

To follow up the difference in the blue channel I then decided to go to the extremes. I upped EV in ACR to +1,80 - still avoiding any clipping but making differences more prominent this way, and chose a corrected white balance for the musical clock on the right of the pic - that was 2000 Kelvin; remember the clock was lit by the candles only! I then took the two pics with the most extreme WB - the Tungsten one with originally 3050 and the Shadow one with 6550. Here a crop of those two:

You see now a visible difference between the two pics. In spite of being developed with identical values the one that had Tungsten WB has a brighter blue channel; the Shadow one has an overall warmer look because of its darker blue channel.

Frankly I still find the difference of those two shots under those rather extreme conditions (raised EV, opposing presets, color temperature lowered rather extremely) not that pronounced. Yes, there is an influence, but have a look here - I just upped color temperature a tiny little bit on the Tungsten WB pic from 2000 to 2100 to get almost identical renditions:

Interestingly enough the other way round isn't possible - in ACR you can't lower color temperature below 2000, so the Tungsten WB pic indeed has a little bit more headroom for adjustment here.

My personal conclusion: It may be a good idea to go the preset or manual balance way in rather extreme conditions. For normal conditions I think adjusting WB for RAW shooting is not called for. In camera that is.

And of course you're invited to draw your own conclusions here!

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Phil

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