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02-26-2009, 08:34 AM   #1
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IsaacSteiner's Avatar

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Location: Stouffville, ON, Canada
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Pentax-M 40mm F2.8 - Mark/stain on glass?


I have a Pentax-M 40mm F2.8 lens, and at the back of the lens, near the mount, that area of glass has this purple/blue ring around the outside of glass? But it's inside the lens. I went to trade the lens in for something else at Henry's, but they wouldn't trade it because of this little mark or stain.

I attached a photo, so you can see what I'm talking about. It doesn't affect the image or image quality, but I'm curious what it is.



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02-26-2009, 11:45 AM   #2
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
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I strongly suspect element separation. This is what my copy looks like:

The rear two elements in this lens are glued together. The glue can sometimes break down and cause this problem. A professional repair would likely exceed the value of the lens.

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