What are the artifacts in this image?

[teekay]

(previously posted incorrectly in the G series forum)

This is a portion of a JPG image I took last night with an A75, otherwise unedited. What are the circular artifacts that show in random places, sizes and opacity? I have never seen anything like it before when using either using my G1 or this A75.

Settings: ISO 100, flash with redeye on, AUTO, slightly zoomed in. I have checked the lens and it is clean. There was no dust or smoke in the air.

http://community.netidea.com/teekay/temp/artifacts.jpg

So...ectoplasm? Help, please!

[dbump]

Just looked at that image, and am puzzled, especially that they change location/appearance. The only thing I can think of is some sort of dust on the sensor (typically only a problem in DSLRs, of course) that moves around when the camera is moved?

If you take multiple exposures without moving the camera at all(mount it on a tripod?), do the blobs continue to change, or are they more static?

[Belmondo]

Well, it looks like lens flare to me, so it might be reflection off something in your picture, or a bright light somewhere in the room.

I'd try taking pictures in a variety of lighting situations, indoors and out. See it it repeats.

[teekay]

Here's a composite image of some of the things, enhanced but all to the same scale. I will take some test shots this evening, same lighting but vary several factors.

http://community.netidea.com/teekay/temp/artifactdetails.jpg

My own theory is tiny UFOs, invisible except by flash, crewed by micro observers from the planet Nano. No wonder so many unwanted pregnancies :-)

[marshall009]

Possibly flare from the buttons and watch?
Mike

[marshall009]

I've just had a closer look at this....
Is there a mirror behind the photographer?
is it possible that the super-bright buttons (which do appear to have a central feature that could account for the donut effect) have reflected back into a mirror behind the photographer, which has then re-reflected the images forward onto the wall in front (and also, in fact, onto the figures in front?

If the mirror had facetted or bevelled edges this could have caused multiple "ghosts"

Mike

[pradeep1]

See my similar question asked last week:

http://photography-on-the.net/forum/showthread.php?t=56907

[Avalonthas]

Its either one of two things. 1) ur lens is dirty, might not be on the outside, but there might be something on the inside. 2) Simple lens flare off of a piece of jewlery.

Easiest way to determine which one it is, is to take another shot somewhere else and see if the same result occurs and/or if in the same place. Peace :p

[dbump]

Pradeep, it does look very similar to your examples--thanks for the link! I've been wondering how much mutli-coating helps, and the examples halfway through that thread were very informative!

[teekay]

Thanks for all the suggestions - it's an intriguing problem.

I took some more test shots last night in the same place, again all with flash. Some with room lights on, some not. This time there were no people, buttons or jewelry in the picture. The lens was and is clean and there is no mirror in the room.

Results: same artifacts all over each image. I now think it *may* be due to reflections from the picture window behind the curtain directly in front, even though it is a fairly heavy, lined curtain.

Will try again tonight with and without flash, and in a different location as I'm determined to find the cause eventually.

[Ikinaa]

I had this effect (multiplied by 100) once in a WWII-Tunnel (digged in the mountain) in France. Temperature was about 5-10 C, humidity 100 and you could smell the dust.
A picture with flash gave my hundreds of gray spots in the picture, without flash (long exposure) it was fine.
Unfortunately I didn't keep the pic.

I'd say it's the light reflected by some dust-particles not too far away from the lense.

[teekay]

OK, I'm now sure I have the the answer and it's definitely not dust particles in the air.

I took more test pix last night and the only time these artifacts appear is when I take the photo, with flash, directly in front of the curtain covering the picture window. At ten feet away I get artifacts. At twenty feet away, zoomed in, I do not, nor when taken closer at at angle to the window.

Clearly at fairly close ranges, at 90 degrees to the window, the flash is strong enough to penetrate the curtain and liner and reflect back causing lens flare.

So now I've learnt something new: Don't take flash directly facing windows - even if they have curtains.

Again, thanks to all for the suggestions.

[cferrero]

I get these artifacts too with my A70, always when using a flash in low light. I had always assumed it was reflections from dust particles.

[boostick4]

I have the same problem with my s500 when it is humid or somewhat dark and the flash is used. Almost always happens outside. Is this common in compact canon digital cameras? It happens often enough that it is a problem for me....very annoying.


Woody