Quick help for a buddy, probably an easy answer...

[1limited92]

He asked if this was from a dirty lens/sensor. He said it happens against dark backgrounds with flash.

 

[Koomoo]

go indoors and take a picture in a dark room with flash. test it out

 

[Fedaykin]

Yep, looks like it. Get something like [ame="http://www.amazon.com/LensPEN-LENLP1-Lens-Cleaning-System/dp/B000KO0GY6/ref=pd_sim_p_3"]this[/ame], or [ame="http://www.amazon.com/Giottos-AA1900-Rocket-Blaster-Large/dp/B00017LSPI/ref=pd_bxgy_p_text_b"]this[/ame](or both) to clean that up.

Or rather tell your buddy to get it. Does his camera have a self cleaning system for the sensor?

 

[KmH]

I don't think those are on the sensor. Sensor dust is dark.

They look like they are lit by the flash.

I think they are on the front of his lens.

Actually, I think they are on the inside of a filter he has on the front of the lens.

 

[Dwig]

I don't think those are on the sensor. Sensor dust is dark.

They look like they are lit by the flash.

I think they are on the front of his lens.

Actually, I think they are on the inside of a filter he has on the front of the lens.

I agree that it looks like close out-of-focus "stuff" that was lit by the flash. To be lit by the flash they can't be on the lens or filter.

This type of spot is common when there is a very light drizzle or mizzle. It can also occur when there is thin coarse smoke particles near the lens but far enough away to be in the beam of the flash.