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07-01-2011, 12:04 AM   #1
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Wild aperture value with 2x Tamron Pz-AF MC7 TC

I am having some weird problems with my 2x Tamron Pz-AF MC7 TC. If I mount this TC to my K20D with any Pentax A lenses or Tamron Adaptall-2 lenses with PK/A adapter, I see aperture values starting from f1.2. For example, Tamron 300/2.8 would show maximum aperture as f2.8 but with the TC in between, the maximum aperture value would start from f1.2, and the same thing happens with Pentax A50/1.7 as well. When an AF lens is mounted with this TC, it works as it should. If anyone has any information or a fix to this problem, I would appreciate your assistance.


07-01-2011, 03:30 AM   #2
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I haven't used a TC yet, however the 1.2 aperture usually shows up like that when the camera cannot read the max aperture of the lens. It looks like your Pentax-A and Adaptall lenses do not report the max aperture to the camera through the TC...I'm not sure why.

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2x, aperture, aperture value, f1.2, k-mount, pentax, pentax lens, slr lens, tamron, tc
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