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.

Here's a couple of test shots (100% crops):

f16:  http://dl.dropbox.com/u/1370864/_IGP3904a.JPG

f8:  http://dl.dropbox.com/u/1370864/_IGP3905a.JPG


Bugger! :-(>

I'm at a loss to know what's causing this but at least I have the Pentax f4 35-70 A zoom to fall back on and it can get nice and close to subjects. At a pinch my Konica Hexanon 55mm macro will work on my Pentax DSLRs if I attach it via a short extension tube. Unfortunately, neither of these gives me the working distance of the Tamron.



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Cheers

Brian

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Brian Walters
Western Sydney Australia
http://lyons-ryan.org/southernlight/





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