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Message: <blockquote data-quote="PapaST" data-source="post: 105102" data-attributes="member: 8330"><p>Take a pic of the clear blue sky at f22 and then scan the image (from camera if you'd like) at 100%.  Just move the "view box" up and down the image in a sweeping motion and see if you notice any dark speck marks.  Those speck marks are dust or some type of oil/debris.  It's not so much that it HAS dust but that it accummulates quickly.  So a one time test isn't complete.  You should check it out and then again after X amount of shutter actuations (maybe 100 - 500 or so).  And see if it's gotten worse, stayed the same, etc.</p></blockquote><p></p>