brown parts of picture

[bodi]

I need help. Am using Sony A700 and a Sony A77 cameras. When using a Sigma 70-200 USM 2.8 lens on either camera approximately 1 out of 3 pictures have the top half/bottom half or parts of the picture a brown color. It doesn't matter the aperature setting. This just started happening. Have had the A700 for a couple years, the A77 and the lens are a couple months old. The contacts are clean. Seem to be from the lens but I don't know where to start. Help

Thanks in advance, Bob

[Manfred M]

It could also be a shutter problem where one of the blades is sticking, but as Andrew has suggested, please post a sample so that we can see what you are asking about.

[bodi]

Thanks for looking and your comments. Bob

These were taken last night in sequence. I'm speaking about the color difference. The light flare ay the top left is from a field light.

[GrahamS]

This can happen when the lamps used in various fittings around the field are not the same - they may look the same to the eye, but to the camera they are different and give a different colour rendition. S.O.L. lamps vs S.U.N vs S.O.X. vs Mercury etc. Just a possibility.

[oldgreygary]

Hello Bob,

Firstly, is the problem only happening with the Sigma 70-200mm lens? Does it happen with your 'standard' lens? You do say that it is happening on either camera which does suggest a problem with the lens.

I noticed that you are using Auto white balance and outputting to JPEG. If you tried shooting the images in RAW format. You could then check in your PP software to see if the camera was resetting the White balance for the shots. Also, you could try manually setting the white balance to one of the settings. Either in JPEG or RAW format you could then see if the White balance was consistent.

if you did some test images with your 'standard' lens, then ran a similar test with the sigma lens you should be able to narrow down what might be causing the problem.

Cheers for now

Gary

[Manfred M]

This looks like an AWB / mixed light situation. We have three different shots with three different colour shifts. Doing a custom white balance or using a preset could potentially stablize the situation; that would at least stop the "hunting" from the AWB.

Bob - can you get the "as shot" colour temperature readings from your PP software to see what the three colour temperature readings the camera used in each of the images?