7D Dirty Sensor? What is this?

Started Jul 7, 2010 | Discussions thread
Jerry-astro
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Try that coffee again...
In reply to Ricky B, Jul 8, 2010

My guess is that the hair is way OOF and not anywhere near the width shown in the image. Your size measurements are not valid, I believe. To get a better idea of what it is and its approximate size, retake an image of a blank surface (blue sky works wonderfully), preferably OOF to help diffuse the image, and stop the lens way down to f/22 or so. That should considerably sharpen what you're seeing, which as others have stated, it sure looks very much like a hair. Now, I am assuming that the image shown was taken at a much wider aperture, so if that's incorrect, I withdraw the comment.

J.

Ricky B wrote:

Brunobl wrote:

Ricky B wrote:

Tom, that artifact looks very wide and diffused which leads me to believe it’s much farther away from the sensor. Check both ends of your lens.

If it were on the lens it would not be visible on the sensor plane. Not even as an out-of-focus smudge. It is probably hair or something like that, just off of the sensor surface.

-- hide signature --

Best regards,

Bruno Lobo.

http://www.pbase.com/brunobl

Hi Bruno,

I surmised it was a hair as well so let me give just a wee bit more information. Based on the area the artifact covers on the image and the pixel pitch (4.3 microns) of this camera sensor, I calculated the area of the sensor covered by the artifact is approximately 216 pixels wide. A hair follicle (I’m assuming human) varies between 25 and 50 microns in diameter which equates to 6 to 12 pixels in width. Sooo! Something magnified that follicle by 24X. Perhaps you could enlighten me as to how that was done!

I must be having a really slow morning. Where’s my coffee???

R

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