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10-07-2014, 01:15 PM   #1
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Focus peaking accuracy?

Does focus peaking loose it accuracy in low light?
Just been out with my new K-3 and focus peaking worked perfectly as long as the light was reasonably good. However, at dusk the camera insisted that the 77 Limited hit infinity focus at the stop at the infinity mark. At the time I found it a strange as this lens focuses past infinity. And true enough, when studying images home at the computer these images are not sharp.

10-07-2014, 01:55 PM   #2
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QuoteOriginally posted by Pål Jensen Quote
Does focus peaking loose it accuracy in low light?
It seems to work fine with my A50/1.2 on a K-01.
10-07-2014, 02:17 PM   #3
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QuoteOriginally posted by Pål Jensen Quote
Does focus peaking loose it accuracy in low light?
Just been out with my new K-3 and focus peaking worked perfectly as long as the light was reasonably good. However, at dusk the camera insisted that the 77 Limited hit infinity focus at the stop at the infinity mark. At the time I found it a strange as this lens focuses past infinity. And true enough, when studying images home at the computer these images are not sharp.
Well, there's certainly a bit of tolerance involved, but since focus peaking just performs edge detection, the only time it won't work is when there's too much noise/not enough light for edges to be visible.

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10-07-2014, 02:33 PM   #4
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I probably reached its limit....
Nice to know.

Does it work with astro photography? Focusing on the moon or stars?

10-07-2014, 03:07 PM   #5
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I don't think focus peaking works very well around infinity and low light for the following reasons:
a) low light means less contrast
b) you are focusing wide open, and generally lenses wide open near infinity appear "soft" (shallow DoF stretched)
These two depend on the lens, though. Since you were using a high quality lens, it probably wasn't this, although it may have contributed. I assume it was:
c) this hits against point b - in live view the camera often stops down, even if the aperture for the photo is wider. This means the DoF in live view is not representative of the DoF in the photo. The way to bypass this is to use DoF preview or to use a manual lens (aperture ring not on A mode). Also, if you press Info or Ok (depending on camera) to get the digital zoom in live view, the camera will open the aperture. This can help with more accurate manual focusing.

I think focus peaking as the Pentax cameras have it right now really needs an update. It was great back when the K-01 came out, but it needs to keep evolving. Pentax needs to improve the algorithms, and add some more options about the peaking colour and sensitivity.
10-07-2014, 03:13 PM   #6
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QuoteOriginally posted by Pål Jensen Quote
I probably reached its limit....
Nice to know.

Does it work with astro photography? Focusing on the moon or stars?
I've tried to use focus peaking on the moon at 300mm, but the camera cant seem to meter properly to get anything useful and it's always just a bright white blur against black. Stars have always been to faint to use focus peaking accurately for me. I usually use regular autofocus to get infinity focus, then I turn off autofocus and take care not to bump the focus ring.
10-07-2014, 03:23 PM   #7
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Yes, focus peaking can work fine with astrophotography *if* you use at least 10X magnification on the Live View screen and a bright enough star (1st magnitude or brighter). However, it works just as well without focus peaking and the magnified Live View image. I trust my Bahtinov Mask more than focus peaking for astro, though.

Jack.

Last edited by jbinpg; 10-07-2014 at 05:43 PM. Reason: spelling
10-07-2014, 05:04 PM   #8
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Why not just set the lens to infinity manually for Astro pic's?


Last edited by bossa; 10-07-2014 at 06:55 PM.
10-07-2014, 05:32 PM   #9
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QuoteOriginally posted by bossa Quote
Why not just set the lens to infinity manually for Astor pic's?
Many of my lenses focus past infinity. So you just can't crank the focus ring till it stops. Where exact infinity focus is on the focus scale is also temperature dependent.

Last edited by Pål Jensen; 10-07-2014 at 05:38 PM.
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