sensor cleaning

I was asked recently how to take a test shot to find out if you have any dust spots on your sensor, here is my reply


You want pick something plain - clear sky, flat light coloured wall, white piece of paper.

Pick your lens that goes to the smallest aperture (the smaller the aperture (higher F-stop) the more likely these are to show up) and set your camera in either Aperture priority or full manual and take two test shots

one at the smallest aperture possible - this will show every piece of dust, I then ignore this photo but it's up to you, I only take it just to see the difference.
another at F16 - this is usually the smallest aperture I go to (after that you get diffraction reducing sharpness) and see what appears.

If anything shows up at F16 then I clean my sensor.

Then repeat the test shots and see if anything shows up, but don't worry about what is there on the smallest aperture shot if you never shoot using it.

If you have paid to have it cleaned then both shots should be clear.

I will add some photos of test shots next time I clean my sensor.