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09-15-2011, 07:52 AM   #1
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SMC Takumar 50/1.4 blades

I've recently purchased an smc takumar 50/1.4 off of ebay. It is really sharp and easy to focus, but there is an issue with the iris blades, and I'm wondering if that is just the way this lens is, or it is an issue with my copy. I should post a picture, but let me try to describe the issue. When I set the aperture greater than 1.4 but less than 2.8, it is like the blades don't fully overlap, and the iris has a kind of irregular shape. The pictures turn out OK, but the bokeh looks kind of funny. At 2.8 and narrower, the blades fully overlap, and I get a nice regular octagon -- there are 8 blades.

If need be, I'll take a pic and post it.
You could also take a look at this picture on flickr.....you'll see the bokeh patter at least, which is identical to the shape of the iris opening.

http://www.flickr.com/photos/proof_by_contradiction/6147885814

Thanks,
Victor

09-15-2011, 08:32 AM   #2
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Actually, that is the design of the blade. The finger tip is exposed or on my copy and it seems as well as yours when set to F2.0. So at F1.4 the blades should be retracted fully. At F2.0 you have a partial extension. At F2.8 the fingers dip out of sight. Unless you have a rounded aperture lens, this is unavoidable.
09-15-2011, 11:15 AM   #3
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My SuperTak 50/1.4 and FA50/1.4 are exactly the same way. That's perfectly normal with this iris design. Nothing to see here, move along...
09-15-2011, 12:27 PM   #4
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something similar seems to happen with the M 50 1.4:

Pentax-M 50mm F1.4 Reviews - M Prime Lenses - Pentax Lens Reviews & Lens Database

See the review by nickthetasmaniac on the 1st page

09-15-2011, 01:12 PM   #5
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Thanks for your answers. That clears that up, then!!
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