Strange (large) dark spot appeared randomly in a couple photos?

[nickds7]

So with my relatively new 7d I had a few random dark spots show up in a couple pictures. Was shooting at someabandonedwar base (not saying that was the cause [:P]). It was hot out (actually it was ~108) , but shouldn't a 7d do ok in the heat?

Only shot ~50 photos that day, only 3-4 photos showed with the dark spot..





B&W helps show the spot a little



black levels raised even further in this pic to bring out spot





Thankfully I didn't care about this shot much... just don't want this to occur again


Any ideas appreciated. (and yes optics were clean, shot at 24mm with 24-70 2.8L)

[Daniel Browning]

My guess is sensor dust.

[elmo_2006]

My guess is sensor dust.
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+1

[nickds7]

Thanks for theresponsesthis late(go to bed!)

Even testing for sensor dust, this doesn't appear. Could have already fallen off the sensor though. Though i must admit, Ihaven'tchanged lenses once since purchasing new.

[neuroanatomist]

Thanks for theresponsesthis late(go to bed!)

I get up early. [:P]


Concur that it's sensor dust. Looking at the scene, you were probably shooting a narrow aperture for deep DoF and with the blue sky in the top half of the frame, well, at least for the bottom half of the sensor you were testing for dust with that shot, even though that wasn't quite your plan.Even if you haven't changed lenses, and you're using a weather-sealed lens and body as you are, the 24-70mm is an extending zoom - that means zooming moves optics - and air. When you zoom wide, the barrel gets bigger - no vacuum, is created inside, so air must come in, right? Despite the seals, that air might bring dust along for the ride.

Could have already fallen off the sensor though.

Every time you turn on or off your 7D, it vibrates the sensor so it very well may have come off already. But, if you haven't changed lenses, the dust speck could still be in your mirror box.


I recently bought aVisible Dust Arctic Butterfly 724 Super Bright - I haven't used it yet because I haven't needed it. But at some point I will need it - with a dSLR, even one with ultrasonic sensor cleaning vibrations, sensor dust is like death and taxes - so I wanted to be prepared.