On Mar 23, 2012, at 2:07 PM, Brian Walters wrote: > My Tamron 90 mm 2.5 has been one of my favourite lenses for decades but it > has developed a problem. > > I was using it a week or so ago and when I downloaded the images I noticed an > out of focus blob right in the middle of the frame. A dirty sensor was my > first thought but the same thing happened when I tried it on a second camera. > > The problem is that the lens looks almost completely clear. I can see a few > small specs of dust but no fungus or haze that would be causing the issue. > The 'blob' is not especially noticeable at large apertures but as I normally > use it stopped down, it is a real problem.
My first thought is that maybe something is delaminating inside of it. I'd be interested to see how it looks photographing a linear grid to see if there is any distortion. Is it the 90/2.5 macro? If so, then maybe some photos of graph paper. Also, does it make a difference if the subject is back lit? I also can't tell how much of the frame that really is, can you show one that isn't a 100% crop? What it almost looks like is shooting through a drop of water. -- Larry Colen [email protected] sent from i4est -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
