i first noticed this issue when trying some very long exposures - 30 minutes or so - and i figured that it was due to the sensor getting warm or something. so i just figured to reduce the exposure time. the following picture is a 30 minute exposure with the lens cap on, just so its clear, two reddish bands running across the image :
i went out today and tried some shots with a 10 stop filter, but to my surprise the very first shots i took at a mere 30 seconds, produced the same issue. this is today at 30 seconds :
oh no! i thought, and dropped to 10 seconds, and for the rest of the day, it was hit and miss. sometimes my 10 second exposures had no strange colors, and sometimes they did have them, it seemed to be quite random. sometimes it is there, and sometimes it is not so i am guessing that perhaps it is not related to heat?
10 seconds today :
just 5 minutes after taking the above picture, i took another few 10 second exposures with no problems at all. for comparison, this is a normal shot so you can see that the boat is not red at all in real life :
its annoying to buy the equipment for long exposures, then find out you cant take them half the time ;D