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04-19-2011, 12:01 PM   #1
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FA 77 limited aperture question

Dear Pentax Forum community,
Just a brief question. It might sound stupid but I need your opinion.
So I got FA77 limited few weeks ago and yesterday noticed that the blades are not precisely aligned that is obvious when the aperture ring is closed. Two blades looks bigger then the other. It is not like a big problem coz lens woks great but it just bother me.
Would you consider this as a problem?
Thanks in advance.
Best regards,
Yuriy

04-19-2011, 12:07 PM   #2
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you might want to ask pentax service in an e-mail whether the aperture shape is typical of the lens or not.

I have seen many times that at extreme small apertures the blades don't always close to form a perfect geometric shape, but the lens still works and the overall exposure is good, so unless you have a warranty issue, it is probably OK, but you need to establish when the issue was noticed and when pentax (or the seller if not bought new) was notified so that you can easily establish the date when the defect is noticed, if the lens fails some time soon.
04-19-2011, 12:18 PM   #3
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Thanks a lot. I got it new from B&H. I will follow your recommendation and will contact Pentax. I saw similar things in the case of some of my older lenses but have not expected that it will be the case with brand new FA77
Thanks again.
04-19-2011, 02:43 PM   #4
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All of my FA limiteds have assymetrical shape when the aperture is closed. I found some threads that discussed this - seems to be quite common. I would not worry about it. Interestingly the FA 50 1.4 I had was perfect in terms of symmetry.

04-19-2011, 02:53 PM   #5
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looks like many has this (my 31 and 15 do). i saw pictures of perfect aperture on limiteds. but you did not buy limited to shoot it at closed aperture anyway...
04-19-2011, 03:02 PM   #6
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Yes, my FA50/1.4 did have well matched blades, as well as DA15. I found mismatched blades on FA77 and SMC Takumar 55/1.8.
And yes, limited lenses are definitely not for closed aperture use, but stopped down to f4 or further it might affect the bokeh in certain conditions? Am I wrong?
04-19-2011, 03:21 PM   #7
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I just checked my 43, 77 & 31. All three seem to be symmetrical when closed, near as I can see, for what it's worth.
04-19-2011, 04:38 PM   #8
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Pretty much all my Pentax lenses have asymmetrical aperture shape when fully stopped down. So long as the widest few stops are good, there is nothing to worry. The chance of getting a perfect sample is pretty slim imho, if existed at all.

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