What is this on my 40D images?

Started Mar 30, 2013 | Questions thread
Jerry-astro Forum Pro • Posts: 10,000
On other small point...

Dale Garman wrote:

If you want to check for dust, then take a picture a clear blue sky or other similar scene.  Then blow it up and move through the image in a systematic way and then you will see if you have dust.  you will often have dust that you don't see since it doesn't generally show up in darker more detailed scenes, but sure shows up in skies and skin tones.

I might add a small point, Dale, if that's OK.  You'll get better and easier to see results if you shoot that blue sky at a very small aperture (like f/22).  That's not recommended for general photography, however, in this case, it will help bring out and clarify any dust on the sensor by vastly increasing the DOF of the shot.

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