black dots - help identify the source

Started 2 months ago | Questions thread
petrochemist Senior Member • Posts: 2,669
Re: black dots - help identify the source

Sensor muck is more noticeable at smaller apertures & is easiest to spot if you take a photo of a uniform pale area (a white wall works well) Its actually best if the subjects out of focus & you use minimum aperture (camera shake is not an issue).

Muck will show as dark spots always in the same place.

If you open the aperture & repeat the test the dark areas will be larger & more diffuse, even to the point where you can't see them. If the size doesn't vary with aperture it could be dead pixels but I don't think I've ever seen this.

It's very rare for muck on the lens to show at all with this sort of test - the muck is so much further from the sensor that it doesn't cast a sharp shadow even at f/64.

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