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12-19-2009, 04:10 AM   #1
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Aperture Blade Circle of DA* 300mm not round?

This is a photo of my DA 300mm taking a picture of itself, two times at f7.1, last one is f9.0
Please have a look at the aperture blades.
i dont expect a perfect circle of course, but shouldn't the circle be more roundly, especially down left?











Last edited by Deimo; 12-19-2009 at 04:32 AM.
12-19-2009, 04:36 AM   #2
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Without having experience with that lens in particular, I can say that in general that's a normal shape/appearance for the aperture of a lens. Also note that the "irregularities" you see are going to be magnified quite a bit, appearing to be worse than they really are, due to the design of a long, wide tele lens.
12-19-2009, 04:58 AM   #3
Dom
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What you've got there is completely normal.

You'll have to spend a lot more money on lenses if you want a round aperture. Not even my 77mm Limited has a round aperture.
12-19-2009, 05:03 AM   #4
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Thx for your answers.
Especially in the first picture the aperture looked a bit weired to me.
But maybe ist was mainly cause of the reflection.

12-19-2009, 05:36 AM   #5
Dom
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This is an 8 blade aperture and as you can see it's not round either.






P.s. 9 blades on any lens is bloody good.
12-19-2009, 06:06 AM   #6
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QuoteOriginally posted by Dom Quote
What you've got there is completely normal.
You'll have to spend a lot more money on lenses if you want a round aperture. Not even my 77mm Limited has a round aperture.
Yes it's typical for Pentax lenses. However, the choice of aperture blades has much to do with the designer's preference rather than a cost issue I believe. I once had a Tamron SP 35-105/2.8 which had pretty circle aperture shape from just 9 blades too. No Pentax lens has ever had such feature. I guess their designers just thought it wasn't important.
12-19-2009, 07:31 AM   #7
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The new DFA 100 macro WR has round aperture.
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