Kill my orbs! Please!!!

August 22, 2008 8:38 AM

Digital photo filter (-orbs, please!): What's with the light blotches that have suddenly started appearing in my pix of very dark things?

You can see that they appear in the same place on subsequent pix (examples 1,2, 4), but then in another session (3), they'll be in different positions, sometimes circular, sometimes not. No flash is involved; tripod and long exposures w/high f-stops. Canon 10D. Sensor dying? Lenses dirty? Sensor dust makes dark spots, not pale blotches, right? Bonus points for a good Photoshop fix (can't send camera out before finishing current project!); simple dodge/burn tool use not quite cutting it... Thanks!

posted by dpcoffin to technology (3 comments total)

It is hard to tell, but could be dust on the lens, which is usually hard to spot in pics because it appears as very out of focus blurs. I was prepared to say lens flare but it doesnt look like that to me. Sensor dust would be small dark spots so that isn't it either. A dying sensor can do some strange things but I do not know if it can cause what you have.
posted by TedW at 8:54 AM on August 22, 2008

I'd doubt that they're a 'digital' problem like a bad sensor. It looks like something tangible, like dust or light spots. But you're right, sensor dust is normally dark spots on light areas, not light spots on dark areas.

I'd give the lens a good look. Actually, next time it happens, throw the lens cap on and take the same picture. If the white splotches go away, it'd make lens dust seem much more likely. (And if, for some reason they don't go away, you could use the black-with-white-orbs frame and get creative with layer masks to try to undo the effect in Photoshop, no? Layer makes aren't my thing, so I can't give superb advice.)

Are you shooting through a filter? (Even just a UV filter?) I used to keep a cheapo UV filter in front of my lens, until I started getting really weird ghosts all over my photos caused by light reflections. (Plus, it's one more thing to get dirty.)

If you have something like lens paper, I'd give your lenses a good wipe, and don't forget to check the rear element. (But also, don't forget to be careful of the rear element!) You might even hold the lens up to light and look through it: has dust crept into the middle? In a pinch, I've used my cotton T-shirt to wipe a lens, though it's probably not the best.
posted by fogster at 9:14 AM on August 22, 2008

Looks like crap on your lens. Check front and rear surfaces, clean with a drop of distilled water and a q-tip or pec-pad. If dust is inside the lens assembly, you're screwed until you get it cleaned professionally, but reducing your f stop will make the problem less obvious until then.
posted by seanmpuckett at 9:15 AM on August 22, 2008