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01-23-2016, 05:14 PM   #16
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I own the Sigma 18-35mm lens and the highly rated SMC Pentax-FA 20mm F2.8 lens.

Over the last two days I have been testing the two.

The Sigma zoom at 20mm is better than the Pentax 20mm lens in overall IQ, especially sharpness.

The dynamic range of the Sigma is impressive. Similarly exposed shots with each lens on my K3ii demonstrated that most areas of highlights that the Sigma handled nicely were totally blown out with the Pentax 20mm lens.

Also, at most apertures, the Sigma was sharp and in focus over the entire frame, The Pentax 20mm lens at larger apertures was only in focus in the center, and even at the smallest apertures, the edges and corners on the Pentax 20mm lens were soft and blurry.

01-23-2016, 06:22 PM   #17
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QuoteOriginally posted by WPRESTO Quote
Excuse on the basis of an aging film shooter who can only think of 28-35-50-55.
Or an RF photographer like me who mostly thinks of FL in regards to rangefinder framelines. 28~50 35~75 90~135

QuoteOriginally posted by Fenwoodian Quote
The dynamic range of the Sigma is impressive.
Dynamic range is not an optical property. The contrast range represented in an image is a result of accurate exposure and the inherent contrast range the sensor is able to record.

QuoteOriginally posted by Fenwoodian Quote
highlights that the Sigma handled nicely were totally blown out with the Pentax 20mm lens.
This indicates the sigma lens was transmitting less light than the prime lens was. Lower T. Stop, this is not a favorable property.
01-24-2016, 06:01 AM   #18
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QuoteOriginally posted by MRCDH Quote
Dadipentak, what has your experience been with the 18-35? Didn't you have any autofocus issues?
No issues--but then, I'm not the sort who goes looking for them. I really fell in love with the lens when I took it for a walk along a local stream on a gloomy day last Spring.



01-24-2016, 02:33 PM   #19
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QuoteOriginally posted by dadipentak Quote
No issues--but then, I'm not the sort who goes looking for them. I really fell in love with the lens when I took it for a walk along a local stream on a gloomy day last Spring.


very nice shots; one can not find any faults with success. It appears you got a good lens which performs the way one would expect.


Last edited by MRCDH; 01-25-2016 at 08:08 AM.
02-14-2016, 02:08 PM   #20
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Any news?
There is a solution for bad focus or not?
02-15-2016, 09:03 AM   #21
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From what I have read the best technique is to focus using Live View, i.e. contrast detection instead of phase detection.

Last edited by GSWayne; 02-15-2016 at 05:34 PM.
02-15-2016, 09:43 AM   #22
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Ehhh
Thanks!

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