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04-12-2014, 05:44 PM   #1
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Is indoor lighting auto focus improved?

Hi k-3 owners....

I have a k10d and k7. I love them to death, but indoors they misbehave badly. Both miss focus really wildly under indoor lighting. Yesterday I did a bit of chimping and found the camera was focusing 3m behind my subject, which was 3m away. The hall had an unfortunate mix of fluorescent, tungsten, halogens and lots of windows letting in daylight. Switching WB to tungsten mostly alleviates the situation, when under the tungsten lighting.
In short - is this nuisance fixed on newer bodies like the k-3?

Best regards,
Cal

04-12-2014, 08:03 PM   #2
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When it comes to low light focusing, the K3 is outstanding. Quite a few notches above anything else.

As for speed, all the DA* lenses are slooooooooooow focusing lenses, so it sometimes kind of negate the focusing ability of the K3.
04-12-2014, 08:24 PM - 1 Like   #3
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There were some reports of front and back focusing with the k5 in artificial lighting, but from the k30 forward, apparently this issue has been resolved.
04-12-2014, 09:39 PM - 1 Like   #4
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QuoteOriginally posted by calsan Quote
is this nuisance fixed on newer bodies like the k-3?
Yes. K-30, K-5 II, K-50, K-3 all solved the 'tungsten AF' problem, and it's variants, that plagued the K-5 and older cameras (although, funnily enough, not the K-x so much).

K-5II and K-3, with their -3EV AF, also focus much better in low-light too. My K-3 will grab focus in places where my K-5 would struggle.

04-12-2014, 10:39 PM   #5
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In their review, Popular Photography noted that the K3 focusing spec was lower than they could test, but that it worked at -2ev. I can't test it either but i'm amazed at the low light where it can still focus.
04-12-2014, 11:30 PM   #6
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My K-5 II managed to lock focus at around -3EV, possibly lower. But don't count on shooting in near darkness - the exposure metering stops working correctly at around 0-1EV. That -3 EV exposure needed a +4 compensation.

Last edited by Giklab; 04-12-2014 at 11:47 PM.
04-13-2014, 01:37 AM   #7
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QuoteOriginally posted by Giklab Quote
But don't count on shooting in near darkness - the exposure metering stops working correctly at around 0-1EV.
The K-3 improves on the K-5II a bit. K-3 metering goes down to -3 EV, matching the AF EV range. So, according to the specs, with the K-3 if you can focus on something even in dark places, you can meter it properly too.
04-13-2014, 02:54 AM   #8
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QuoteOriginally posted by rawr Quote
The K-3 improves on the K-5II a bit. K-3 metering goes down to -3 EV, matching the AF EV range. So, according to the specs, with the K-3 if you can focus on something even in dark places, you can meter it properly too.
If this works in real life then great, but I suspect you'd still need some compensation. In my experience, the K-5 starts bugging out at around 3-4 EV already (needing +0.7) and needs a progressively larger positive compensation as light levels drop. I would thus assume that the K-3 is accurate to about 1-2 EV.

04-13-2014, 02:59 AM   #9
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QuoteOriginally posted by flyer Quote
When it comes to low light focusing, the K3 is outstanding. Quite a few notches above anything else.

As for speed, all the DA* lenses are slooooooooooow focusing lenses, so it sometimes kind of negate the focusing ability of the K3.
Yep, SDM is not fast. But if you are pleased with AF performance in good light (which reflects the max speed of the lens), upgrading to a K-5 II or K-3 will improve the speed in low-light (which was hindered by the camera's AF system).
04-13-2014, 04:20 AM   #10
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QuoteOriginally posted by Giklab Quote
My K-5 II managed to lock focus at around -3EV, possibly lower. But don't count on shooting in near darkness - the exposure metering stops working correctly at around 0-1EV. That -3 EV exposure needed a +4 compensation.
Except that is not how the specification works

The specification is -3 EV (at ISO 100, with a 50mm F1.4 lens)
As soon as your using a less capable lens the light level you require goes up to easily ahievable levels
With an f5.6 lens the camera will cease to focus at EV1

So though the camera has one of the most sensitive af mdoules in the world it can still hit the end stops in reasonably low light with slow kit lens (da55-300 put your hand up)
04-13-2014, 05:33 AM   #11
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Thanks everyone - I'm not worried about speed, or performance in low light. I just want focusing to actually focus on the selected subject.
Sounds like it's fixed.
04-13-2014, 05:38 AM   #12
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QuoteOriginally posted by awaldram Quote
Except that is not how the specification works

The specification is -3 EV (at ISO 100, with a 50mm F1.4 lens)
As soon as your using a less capable lens the light level you require goes up to easily ahievable levels
With an f5.6 lens the camera will cease to focus at EV1

So though the camera has one of the most sensitive af mdoules in the world it can still hit the end stops in reasonably low light with slow kit lens (da55-300 put your hand up)
Umm... Yes, the specification is measured with an 1.4 lens, but the AF module still works down to -3 EV measured in camera (In my case, ISO 51 200 at f/5.6 at 2 seconds). The actual light level is of course higher in my case.
Which means the AF is even more damn impressive if you mount an 1.4 lens .
04-13-2014, 05:53 AM   #13
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QuoteOriginally posted by flyer Quote
When it comes to low light focusing, the K3 is outstanding. Quite a few notches above anything else.
As for speed, all the DA* lenses are slooooooooooow focusing lenses, so it sometimes kind of negate the focusing ability of the K3.
Almost exactly what I was going to say.

Under conditions that would have been a challenge for my K5, I have not missed a shot with the K3 because it was unable to focus.
I have still missed a few with the K3 because the lens is still moving to get where it needs to be. :-(
04-13-2014, 06:16 AM   #14
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QuoteOriginally posted by calsan Quote
Thanks everyone - I'm not worried about speed, or performance in low light. I just want focusing to actually focus on the selected subject.
Sounds like it's fixed.
It's the main reason I'm thinking about upgrading to a K-5II or K-3. Shot some photos with my K-5 at a family gathering last Christmas, and some of those photo's were front-focused. Same with shooting a band at a jazz cafe.
04-13-2014, 07:28 AM   #15
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I always have mixed feelings about the tungsten issues. I never had any focus problems with any kind of lighting with my Kr, my K5 and now my K7. All three are "renowned" for having FF issues. When I bought my K5 second hand, the seller was getting rid of it because: I quote "This f&^$% thing can't focus right". I never, ever, ever had any issues with focusing. And 90% of the pictures I take in winter time are interiors with various types of lighting and usually using auto WB.

I know Pentax admitted having those issues, it almost drove me away from the brand when I was looking at getting back into photography. Reading about the issue on the interwebs made me believe that the cameras were unusable inside. Regardless, I took a chance with a Kr (store had a great return policy). I'm happy I did.

The OP mentioned that his camera is back focusing by a lot, from what I have read, the front focus issue was that the image would be slightly oof due to the AF sensor having issues with the color temperature and wavelength, miscalculating focus by a fraction of a fraction of an inch (not far enough to be visible in the viewfinder). So in this particular case, where it seems that the room was well lit (artificial + natural light) I don't think it is either a tungsten FF issue or the K7 low light capabilities that caused the misfocus. The K7 (and K5 and Kr) focus confirm squares are much smaller than the actual AF area. At 10-15 feet away, doing portraits, often it will confirm focus on the subject eye (little red square) but the camera is actually focused on the nose which is slightly off the red square. (I always use manually selected single point focus)
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