what is this 'mark'....

[413x]

you can see a pentagon on the phone
Shot was tested with a 50mm, 5 blade aperture lens


It isnt always the same size
it isnt on the lens

its on a friends camera

EDT, 50, not 500mm, typo
also tried macro lens etc and still present

 

[413x]

Refraction from lens element?

To eliminate if its dust on sensor. Put a lens on, shoot at something white and wave it around for 10 seconds or so at F 18 or something.

you mean leave the shutter open for 10secs?

Could be a dust bunny on the sensor

thought it might be this

due to my newness to this, why does the mark change size with differing focus if it is in the body?