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04-21-2014, 05:02 AM   #1
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Pentax-M 50mm 1.7: Is that a defect oder just normal character?

Hi everyone,
i have a M 50mm 1.7 lens, that, i feel, has a "glowing" look to hard contrast edges when they are slightly out of focus.
Look at the edges of the paper on my attached picture...
To me they look not like edges that are out of foucs but as if i had faked bokeh by gradually blending a sharp and a blurred image together in photoshop. Not sure if i come across clear? Overall, the paper seems to glow.

Could there be something wrong with my lens, or is that just the look this lens gives?
I could not see similar problems in the pictures from the PF lens review database.

I was using a tripod and a lens hood.
Thanks for your advice
Micha

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PENTAX K10D  Photo 

Last edited by Alcazar; 04-21-2014 at 07:32 AM. Reason: corrected focal length from 55mm to 50mm
04-21-2014, 05:30 AM   #2
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QuoteOriginally posted by Alcazar Quote
Could there be something wrong with my lens, or is that just the look this lens gives?
Perfectly normal. Any fast lens would give a similar look to this shot. You're shooting at a pretty steep angle to the background plane, are focusing close, and using a wide aperture -- all results in a shallow DOF and a rapid transition from sharp to blurred. BTW the Pentax-M 1:1.7 is a 50mm lens.
04-21-2014, 06:37 AM   #3
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Thank you Baro-nite

QuoteOriginally posted by baro-nite Quote
all results in a shallow DOF and a rapid transition from sharp to blurred
yes, i'm fine with the DOF being shallow... it's the quality of the bokeh i'm not sure about. it's not how i know bokeh from my other lenses.

QuoteOriginally posted by baro-nite Quote
BTW the Pentax-M 1:1.7 is a 50mm lens.
correct, my mistake.
04-21-2014, 06:46 AM   #4
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QuoteOriginally posted by Alcazar Quote
yes, i'm fine with the DOF being shallow... it's the quality of the bokeh i'm not sure about. it's not how i know bokeh from my other lenses.
Right, understood. High-contrast edges tend to do that. This lens does have some longitudinal CA (as do most lenses) and the white paper edge is where this will be most noticeable. It's subtle here, but does give the bokeh more of an edge along that horizontal paper edge.

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