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07-10-2022, 05:46 AM   #1
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Should I use live view focus on my K3 for low light shooting?

Yesterday I took test shots with my K3 and da*16-50 using a lens focus chart in my living room, daytime, good reading light. The live view shots are always sharp in focus. The viewfinder shots never as sharp. Same result in manual focus and autofocus. Is this normal for K3 shooting indoors using natural light?

Last week I shot people at indoor train station. All viewfinder spot focus on faces. Back focus lock, recompose, shoot. I also shot at dusk, early evening in bright shopping area streets and in shops. 90% of dogs, cats, and people faces not in focus.

approx. ISO 1600-3200, f2.8-5.2, 1/40 sec.


Last week in the office, bright lighting, viewfinder focus, I took sharp pictures of my coworker. So, faces in bright indoor light, no problem.

Do I need to use live view and Contrast detect focus for lower light?
What is your experience for low light, street evening, shopping mall, train stations?

Thanks

07-10-2022, 06:04 AM   #2
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The most obvious question is:

Have you done autofocus calibration with this lens? And as a follow up; was that calibration done in the same lighting as these shots at the same focal length? Zooms can be toughÖ the fine focus adjustment can be different at different focal lengths.

Another consideration is ISO. higher iso can soften results and make it look like missed focus. Careful examination of the soft shots should show areas of sharp focus if itís just focus being missed.

Final point: the SDM SMC DA* 16-50 and the PLM HD DA* 16-50 are quite different, you may want to clarify which you are discussing. Some K3iii users have reported focusing issues with the new HD DA* 16-50 but it isnít a clear picture to me as I donít own that HD lens or the K3iii; I do own the SMC lens (screw drive converted) and the original K-3 and honestly Iíve not used it for critical shots enough to have noticed if focusing varies based on lighting.
07-10-2022, 09:51 AM   #3
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QuoteOriginally posted by UncleVanya Quote
The most obvious question is:

Have you done autofocus calibration with this lens? And as a follow up; was that calibration done in the same lighting as these shots at the same focal length? Zooms can be toughÖ the fine focus adjustment can be different at different focal lengths.

Another consideration is ISO. higher iso can soften results and make it look like missed focus. Careful examination of the soft shots should show areas of sharp focus if itís just focus being missed.

Final point: the SDM SMC DA* 16-50 and the PLM HD DA* 16-50 are quite different, you may want to clarify which you are discussing. Some K3iii users have reported focusing issues with the new HD DA* 16-50 but it isnít a clear picture to me as I donít own that HD lens or the K3iii; I do own the SMC lens (screw drive converted) and the original K-3 and honestly Iíve not used it for critical shots enough to have noticed if focusing varies based on lighting.
Live view AF will in theory, always be more accurate, presuming it is fast enough, but before you throw out phase detect AF, make sure you have dialed on your autofocus.
07-10-2022, 10:32 AM   #4
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Thanks very much! It is a calibration back focus problem. I looked at my images, and items behind the focus chart seem in focus. I played with AF fine adjustment tonight. At + 8 or +9 the lens focus chart looks good. I will put it on my tripod and check calibration at different focal lengths. My lens is SDM, broken, converted to screwdrive.


So, calibrate for the phase detect, the live view contrast detect system is fine.

07-10-2022, 12:21 PM   #5
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Calibration issues aside, I do think shooting through the OVF and using the dedicated focus sensor (I think that's phase detect?), the dedicated focus sensor is more sensitive than the on-sensor focussing. So in low light, I would prefer that as long as the calibration is good.
07-22-2022, 08:27 PM   #6
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Thanks Uncle Vanya!


I spent a couple of hours fine tuning the lens. Yesterday went out and got some super shots. I have severe a backfocus issue. About +8. The glass is sharp, so before calibration, depending on shooting parameters I either got super sharp or super soft shots. I got enough really sharp pics that I thought that the lens didn't need calibration, and I thought it was all technique. happily, It turns out my technique is "okay".
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