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08-31-2009, 10:03 AM   #1
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Pentax DA 100/2.8 macro lens problem

This picture was taken from my new, unused Pentax F/DA 100/2.8 macro lens' aperture blades. Clearly wisible, the a circle is not round, assymetrical instead.
My question is: this is bug, or feature?!
100/2.8 macro owner's answers are welcome.
Thank you.

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08-31-2009, 10:14 AM   #2
Ash
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Usually, aperture openings are designed to be geometrically symmetrical.
AFAIK all my good lenses are quite regular in this regard, and I have a couple of older no-name brand lenses that look similar to your photo above. Though I couldn't tell you if it is a defect in the lens.
Does it affect your photo quality? Can you have it looked at by the vendor you bought it from?
08-31-2009, 10:31 AM   #3
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there was a thread somewhere about this. Seems it is quite common
08-31-2009, 10:45 AM   #4
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it should be symmetrical. I think some of the blades are misaligned. and I do believe it would affect the outcome of your shots. particularly the precise amount of light that goes thru and could even affect bokeh results as well.

the best thing would be to bring the lens to the shop where you bought it and compare it to the other lens they have in stock.

08-31-2009, 10:58 AM   #5
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QuoteOriginally posted by octavmandru Quote
there was a thread somewhere about this. Seems it is quite common
Hi! Can you help me to search that thread? My english is not so good, and I not properly understand the forum's search engine. Thank you.
08-31-2009, 11:46 AM   #6
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https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/41357-cosina-5...2-club-20.html
08-31-2009, 11:50 AM   #7
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QuoteOriginally posted by switch Quote
This picture was taken from my new, unused Pentax F/DA 100/2.8 macro lens' aperture blades. Clearly wisible, the a circle is not round, assymetrical instead.
My question is: this is bug, or feature?!
100/2.8 macro owner's answers are welcome.
Thank you.
Switch,

I just took a look through my A 100/2.8 macro and the blades are perfectly symetrical. Looks like a flaw to me. If this is a brand new lens I would send it back and ask for another one.

Tom G

08-31-2009, 06:29 PM   #8
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Hmmmmmm...??

Mine appears to be a perfectly balanced opening, when I look straight into the lens. If it's a tiny bit off center, or not square with my eye, it can look distorted.

Also, may I ask what it looks like from about F/4.0 to (say) F/16, the len's sweet-spot range? Is the opening still distorted? If it's balanced, what's the problem?

Cheers...
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