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08-16-2007, 02:47 AM   #1
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Sigma 30mm 1.4 or Pentax 50mm 1.4?

Hi,

did any of you compare these two lenses? Edge sharpness isn't that important for what I'm going to use it for, but sharpness is, and color/contrast. I need a lens in the 1.4-20 range.

08-16-2007, 04:41 AM   #2
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An ol' Calr Zeiss Biotar 58mm f2 / Helios-44X-# MC 58mm f2 suits that purpose very well.

X = "M" for M42 and "K" for K-Mount
# = I suggest to stick with versions 4, 5 and 6.

Already very sharp at f2 and it won't break the bank...at least the Helios won't. :P
08-16-2007, 04:58 AM   #3
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QuoteOriginally posted by dLight Quote
did any of you compare these two lenses? Edge sharpness isn't that important for what I'm going to use it for, but sharpness is, and color/contrast. I need a lens in the 1.4-20 range.
I own both. The Pentax has a more balanced performance.

Wide open, the Sigma is quite sharp in the center and not so in the corners. Corner sharpness improves greatly when the lens is stopped down, but this lens suffers badly from purple fringing. Here are two full size crops, the first taken at f/1.4:


And the second at f/5.6 (CA is still there):


The weather on that day was overcast; you can imagine the results in bright sun!

Cheers!

Abbazz
08-16-2007, 06:22 AM   #4
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As a follow-up to my previous post, here is a reduced full frame view of the picture taken at f/5.6:



You can see that the 100% crop was taken from the middle upper border of the original picture. Sharpness is better in the center of the picture.

I have also the Sigma 20/1.8 and Sigma Macro 24/1.8 lenses. The 20mm is a dog, but the 24mm is a very good lens, which exhibits fine performance even wide open. Chromatic aberration and blooming are very well contained. The best choice in the Sigma range of fast wide/normal primes IMHO.

Cheers,

Abbazz

Edit: The "macro" mode on the 24/1.8 comes in very handy. Minimum focusing distance is 18cm from the focal plane (1/2.7x). At this setting, the front element almost touches the subject. Here are two close-up pictures taken with this lens wide open:





Last edited by Abbazz; 08-16-2007 at 07:10 AM. Reason: Adding pictures
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