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04-24-2010, 09:21 AM   #1
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for pka adapter adaptall shooters...

i thought this would be worth posting.. (or reposting)
The Tamron KA Adaptall Mount

When Joachim Hein read the above discussion, he immediately understood the roots of the exposure problems that some Adaptall lenses have. These are all "slow" lenses with minimum aperture setting of f/22 and an "AE" setting or f/32 and no "AE" setting In the latter case, f/32 is converted to "AE"). "AE" is the Tamron equivalent of the Pentax "A" setting. Looking in the second column of the table above, we see that there is no contact pattern for lenses with apertures ranging between f/4.5 or slower and f/22.
Tamron solves this by making the Adaptall mount indicate a maximum aperture of f/4 and warning in the mount manual that the photographer must watch the aperture read-out in the view-finder (not available with P30/P50!) to ensure that only values within the true aperture range are used.


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adaptall, aperture, f/22, f/32, k-mount, lenses, mount, pentax lens, slr lens, tamron
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