Purple artifacts with 35mm f1.4L on long exposures

[janmaxim]

Hello

Yesterday I experienced a strange problem. I was taking long night exposures of a village in greece with a tripod with exposure time ranging from 5 - 30 seconds.

After the longer exposures (10 seconds+) purple artifacts were visible in the images. They looked like a flare. But they appeared even if I turned around 180 degrees for a new exposure. The same with and without the UV-filter (B+W 080 MRC).

So there is indeed something between the first lens element and sensor causing this. Has anyone any idea of what this is?

I am using EOS600D with some custom functions like ISO noise reduction turned on.

 

[Loswr]

Can you post an example?

 

[Peerke]

Could it have to do with the IR filter of your 600D? I had the same with my 40D until I put a IR filter in front (B&W 486) and the margenta color cast was gone.

 

[janmaxim]

I have three samples here. Sorry for the bad quality, had to take a picture with my ipad from the camera screen. You can clearly see the purple artifacts in the top section of the images.

http://imgur.com/9w1TjVF
http://imgur.com/Zuon0YH
http://imgur.com/5yUPRlU

 

[Pi]

Those are severely overexposed images, for the highlights. Most likely flare. What f-stop?

 

[Mt Spokane Photography]

Those are severely overexposed images, for the highlights. Most likely flare. What f-stop?

Yes, so badly overexposed that they can't be saved. You need to shorten the exposure, use lowest ISO, smaller aperture, and possibly a neutral density filter.