Have a 1DX Mark III. Absolutely in love with it. Spent Friday & Saturday evenings at the local motocross track. Needless to say gear is filthy. Need to take the bag the camera/lens is in out to the garage and use the shop vac to get all the silt off of it before opening the bag and cleaning the camera/lens. Prior to mounting the lens I did a test shot on a white piece of paper to verify the sensor was clean...it was. Started culling the images and saw a repetitive mark.....
Have seen plenty of boogers in my short time of photography but none that look like what I circled. Is that an oil smudge on the rear element of the lens? The lens I used was a 300 f/2.8 L. Last time I used the lens I had swapped the Circular Polarizer into it. It is very possible that I may have put a grubby finger or three on the clear one while swapping it into the lens.
In my experience it is more likely something on the sensor than a fingerprint on the front of the lens.
I'm curious why the image looks like it does.
"How does one get a color negative from a 1D X Mark III. I am not familiar with how to do that."
Photoshop! It doesn't care what DSLR you have, it will make a color negative and it can remove the pole from the rider, too.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
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05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.