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10-09-2015, 12:49 PM   #1
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Is this AWB in action?

Having caught a couple of snaps of the ISS passing over I tried to again capture the stars in my light polluted environment

Both the following pics were taken within seconds of each other, same settings (ISO800, f2, 15sec using SMC 50mm f1.4) The only difference between the 2 pics is that I moved the tripod head slightly more vertical which brought more of the tree into shot. But as a result the sky has gone from Black to a deep Blue - even though the shift on the tripod was minor!

What has caused the difference in colour? The AWB settings?

TIA

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10-09-2015, 12:58 PM   #2
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Heh, sure looks like a WB shift. Don't know why camera decided to shift it, but it probably had some computer-logic reason. WB is difficult to set for astrophotos, so its not too surprising
10-09-2015, 01:07 PM   #3
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it's done the same thing for me also,
Buddy of mine and i were spinning (steel wool) and in half the shots the sparks were a beautiful orange/yellow color (accurate) and in the other half they were nearly pure white. Nothing changed, not even tripod position
Quick LR WB shift brought them right together though.
10-09-2015, 02:56 PM   #4
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Could be an effect of a setting "WB Adjustable Range: C>2>10 on the K5 IIs. Not sure what K50 options are. With this enabled the camera may change White Balance automatically even if WB is set manually. I recall having great difficulty getting a gray card to photograph gray with this feature turned on. I suspect it works mostly on images that have little colour variation as I have found no effect of this this feature on normal scenes. I have set this to OFF in both K-7 and K5 IIs

10-09-2015, 02:57 PM   #5
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Part of what you’re probably seeing is light pollution and part of it is probably the auto white balance interpretation of this light pollution. Unless you are more than 50 – 100 miles from any kind of town or city you will tend to get light pollution. Even a nearby lighted highway can cause problems. This is the kind of things that astronomers have to put up with all the time. Back in the days of film amateur astronomers would have to use special filters to try to reduce the color shift. But nowadays as you can see is much easier to do it digitally post processing.

DAZ
10-10-2015, 11:03 AM - 1 Like   #6
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I'm wondering how much it has to do with the amount of foliage in the corner of the frame.
The first is nearly all sky, the second has significantly more leaves, the AWB algorithm may be reading that and thinking too hard.

Where do you find that much clear sky in Britain?
11-14-2015, 05:37 AM - 1 Like   #7
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QuoteOriginally posted by K-Three Quote
I'm wondering how much it has to do with the amount of foliage in the corner of the frame.
The first is nearly all sky, the second has significantly more leaves, the AWB algorithm may be reading that and thinking too hard.

Where do you find that much clear sky in Britain?
I believe it is the trees. If you have metering set to full matrix the trees will factor into the second image. Since you have more green in the shot you will shift your WB to the blues since blue is opposite of green. Try and set you metering to spot metering for white balance next time and you should not see this.
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