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01-07-2013, 05:32 PM   #1
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Problem with new Sigma 30mm f1.4

Hello fellow Pentaxians
I recently got a new Sigma 30mm 1.4 from B&H and didn't really use it much till now. Now there are some issues I've noticed that are causing me to consider returning it. The attached image shows the aperture blades are not uniform. There seems to be one blade that isn't in place. This causes some of the bokeh at certain apertures to be lopsided and misshapen.
The other thing is that strange circular pattern in the bokeh. I tried cleaning the inner surface of the lens, but it's still there. Any other owners of this lens have these issues? Any idea if it's a problem with this lens or just my copy? Would you return it over this? I appreciate any thoughts Forum members have. Thanks in advance.

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01-07-2013, 05:42 PM   #2
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Are those light sources LEDs, by any chance? I've noticed (with various lenses) that LEDs sometimes have weird refraction patterns, probably due to their built-in lenses.
01-07-2013, 05:50 PM   #3
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QuoteOriginally posted by THoog Quote
Are those light sources LEDs, by any chance? I've noticed (with various lenses) that LEDs sometimes have weird refraction patterns, probably due to their built-in lenses.
They are Christmas lights, not sure if they are LEDs... here's the full image: (and you can see that misshapen bokeh too)
01-07-2013, 06:08 PM - 1 Like   #4
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its very hard to get perfect aperture blades in any lens. with that being said, it should not have a major impact on the bokeh at all. what you're seeing is more inherent to the optical design of the lens itself. the weird circles you see in the bokeh is an optical artifact that occurs when lenses use ashperical elements in their construction, whereas the weird bokeh shapes in the corners are due to the coma, which is a common side-effect of really fast lenses. in extreme cases of coma, you end up with swirly bokeh, which is what you can see in lenses such as the Helios 40-2

01-07-2013, 06:14 PM   #5
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Mine is more of a symmetrical octagon, though not perfect.
01-07-2013, 06:18 PM   #6
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QuoteOriginally posted by adpo Quote
its very hard to get perfect aperture blades in any lens. with that being said, it should not have a major impact on the bokeh at all. what you're seeing is more inherent to the optical design of the lens itself. the weird circles you see in the bokeh is an optical artifact that occurs when lenses use ashperical elements in their construction, whereas the weird bokeh shapes in the corners are due to the coma, which is a common side-effect of really fast lenses. in extreme cases of coma, you end up with swirly bokeh, which is what you can see in lenses such as the Helios 40-2
Very informative! This information has put me at ease with these issues, which I will now consider just quirks of the design. I guess I'll keep it! Thanks for the help!
01-12-2013, 05:48 PM   #7
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I'm still having problems with focus on my copy of this lens. I'm starting to think I should have it calibrated to my camera. I know I can try the fine adjust focus on the very clever in camera system, but I'm not sure I have the skill to do a proper focus test. I live in NYC, surely there's someplace I can walk it in? Adorama where I got the K5, or B&H where I got the Sig 30?
01-12-2013, 07:08 PM   #8
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Sample from today (with toy camera filter)


01-12-2013, 09:14 PM   #9
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QuoteOriginally posted by Adam_T4 Quote
t I'm not sure I have the skill to do a proper focus test. I live in NYC, surely there's someplace I can walk it in? Adorama where I got the K5, or B&H where I got the Sig 30?
Shoot several shots of long subjects at an angle and at f1.4. I use a plain sidewalk that has grass in one of the cracks. The in-focus part is easy to see. I've put +5 on mine.
01-17-2013, 01:26 AM   #10
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The focus sensor is BIG and might as well focus on the leaf beside the one you where aiming for, so to test if the focus is right you have to aim at a large flat area, not several tightly grouped things at different distances.
01-20-2013, 12:22 PM   #11
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focus adjust +4 worked

OK, not to leave a wrong impression here on this lens, if you can deal with some quality control issues, and the aspherical aberrations or coma, and can fine adjust the focus on your body - I added +4 - then all in all this thing is A-OK at the $350 price level. At $500 there's better things to look at, IMHO. 3 stars
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01-21-2013, 12:46 PM   #12
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QuoteOriginally posted by Adam_T4 Quote
OK, not to leave a wrong impression here on this lens, if you can deal with some quality control issues, and the aspherical aberrations or coma, and can fine adjust the focus on your body - I added +4 - then all in all this thing is A-OK at the $350 price level. At $500 there's better things to look at, IMHO. 3 stars
Don't feel bad. I had a similar experience to you. I could not deal with the quality control issues, and I have already sold my Sig 30 1.4 at a loss. People should be informed what they are potentially getting into when they are looking at getting this lens, so it's best to be honest.

I'll be leaving some strongly worded reviews on this lens wherever I can.
01-21-2013, 01:27 PM   #13
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It is quite difficult to attain perfect focus with such a fast lens, even if the adjustment is spot on. And I definitely experienced the same triangular bokeh - yep it's coma. But if you can position your subject so the background is completely blurred, it's a decent APSC version of a FF fast fifty without spending too much or putting up with a huge FF lens.
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