Different amounts of white and color in each of the two scenes. A really good reason (number 49 million) to never use auto white balance.-Kent..

Ablack wrote:.

Image 1 : Canon A530 Mode M, ISO 80, F/3.2, 1/20, Auto WB.Image 2 : Canon A530 Mode M, ISO 800, F/3.2, 1/200, Auto WB.Nothing except ISO and shutter touched. Lighting, - evening inbrightly-lit store, mix of flourescent and incadescent.Why 1st image has way much warmer WB than the 2nd one?(That was not camera store, so they hadn't batteries and card handy,and didn't mind when I hadn't format my own spare SD card after test.(I asked them.) But just in case I post only minimal crops with nofaces or legible texts.).

There can be a number of reasons. The main one , that has already been mentioned is that Auto WB can often show some inconsistencies from one shot to the next as it is effectively making a guess based on the distribution of colors that appear in any one capture..

Also, artificial lights, especially fluorescent lighting can cause it's own inconsistencies, especially at less than fairly long shutter speeds. The light looks continuous to our eyes but is in fact cycling on and off very quickly. It's own color temperature can have some considerable variance from one shot to the next which could effect the color even if you weren't using auto WB..

'Here, look at the monkey. Look at the silly monkey!'.

Tom Younghttp://www.pbase.com/tyoung/..

Well, although it's not evident from the crops both shots had nearly the same distribution of colors in them. (same point, same subject (but she moved a bit), same framing). It alone can't explain such a dramatic change I feel..

Tyoung wrote:.

Also, artificial lights, especially fluorescent lighting can causeit's own inconsistencies, especially at less than fairly long shutterspeeds. The light looks continuous to our eyes but is in factcycling on and off very quickly. It's own color temperature can havesome considerable variance from one shot to the next which couldeffect the color even if you weren't using auto WB..

Probably, that's it. I noticed that LCD had shown "mismatching framerates" pattern at certain shuttrer speeds. Maybe one of the lamps in there is starting to fail, and that further increased CT inconsistences...

Set the WB to tungsten (eliminate WB as the reason) and try a similar test at ISO 80 and ISO800.ISO800 will wash out the reds and yellows I expect..

Colour noise is often extremely saturated..

Underexposed areas in the blue channel correspond to highly saturated yellow (the complimentary colour)..

In fighting colour noise the image processing may well include a desaturtion of some highly saturated colours..

There is at least one compact that more or less kills the saturation completely in the darkest 20 levels..

There is another compact camera highly respected for it's high ISO performance that turn reds into magentas at high ISO..

Andrew..

And there's a LOT of noise in the second image..

But the point about fluoro lights is relevant also..

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Looks like it. I noticed that my new A630 does the same thing at ISO 800, - even with preset WB, in daylight, WB is noticeably "colder" at ISO 800, but not at ISO 400. Although, with that noise ISO 800 is next to useless anyway....

The ounce of passion is worth the pound of work...

It might also be that the heavy noise reduction has desaturated the picture and certain colors were more affected than others. Just a thought.'Be right, fearless, faithfull, and true to others...'T.S. Elliott..

De-saturation from noise reduction. I think there is no other problem..

StephenG.

Pentax K100DFuji S5200Fuji E900PCLinuxOS..