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12-03-2014, 11:43 AM   #1
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k3 low light af accuracy

So how much better k3 is in low light than k5? If I shoot with 55mm with large apertures around 1.6 it is not very reliable with af accuracy. Is k3 a lot better?

12-03-2014, 11:56 AM   #2
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I know my K3 is much better than my K5 with low light AF. I don't know about the lens you are using, but in places my K5 would give up completely my K3 locks on.
12-03-2014, 12:00 PM   #3
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QuoteOriginally posted by sran Quote
So how much better k3 is in low light than k5? If I shoot with 55mm with large apertures around 1.6 it is not very reliable with af accuracy. Is k3 a lot better?
My K-5 and K-3 are a night/day difference in focus accuracy in low light. I shoot the occasional wedding and the K-5 could never hit my target in the dark reception hall. Always front/back focusing. The sensor was great for the dynamic range and exposure latitude it provided, but if the focus was off, none of the IQ benefits mattered. The K-3 nails it almost everytime. Its so so much better. The af-c speed is still too slow for much use to me. But the sensor is just as good, especially if you downsize to 16MP in post.
12-03-2014, 12:06 PM   #4
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I though the K-5 was good but the K-3 is much much better.

12-03-2014, 01:22 PM   #5
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QuoteOriginally posted by enoeske Quote
My K-5 and K-3 are a night/day difference in focus accuracy in low light. I shoot the occasional wedding and the K-5 could never hit my target in the dark reception hall. Always front/back focusing. The sensor was great for the dynamic range and exposure latitude it provided, but if the focus was off, none of the IQ benefits mattered. The K-3 nails it almost everytime. Its so so much better. The af-c speed is still too slow for much use to me. But the sensor is just as good, especially if you downsize to 16MP in post.
K5 is doing exactly like that, it locks but to wrong spot. Would you say k3 is on same level in accuracy as contrast focusing?
12-03-2014, 01:24 PM   #6
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QuoteOriginally posted by sran Quote
K5 is doing exactly like that, it locks but to wrong spot. Would you say k3 is on same level in accuracy as contrast focusing?
Probably not as accurate (for technical reasons) but certainly close and a lot faster.
12-03-2014, 01:34 PM   #7
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The K-3's low light AF sensitivity is the -3 EV(100) which is the same as the K-5 II/IIs. That is 4x more sensitive than the K-5.


Steve

---------- Post added 12-03-14 at 12:37 PM ----------

QuoteOriginally posted by sran Quote
K5 is doing exactly like that, it locks but to wrong spot.
That is not related to AF sensitivity and can happen regardless of how much light is present. Use fixed point AF if you need full control.


Steve
12-03-2014, 01:43 PM   #8
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QuoteOriginally posted by stevebrot Quote

That is not related to AF sensitivity and can happen regardless of how much light is present. Use fixed point AF if you need full control.


Steve
The K-5 had a well known low light tungsten bug where autofocus would lock but would front or back focus. Very inaccurate in wedding reception style light. In typical brighter light, autofocus was fine.

12-04-2014, 05:14 AM   #9
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Funny how the K5’s AF problem is a well-known fact now, but when some of us complained about it when the camera was relatively new we were pretty much dismissed as morons.
12-04-2014, 05:48 AM   #10
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For me the best combination for fast focus and accuracy is K5IIs + 77 (for portraits). Spot on in low light, in back light....prefer that to K3. But when I shoot with 16-50, I find it to do better with K3.
12-04-2014, 06:22 AM   #11
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QuoteOriginally posted by enoeske Quote
The K-5 had a well known low light tungsten bug where autofocus would lock but would front or back focus. Very inaccurate in wedding reception style light. In typical brighter light, autofocus was fine.
Is there anything that could be done to improve it? Anything that would make it back focus always or front focus always. Currently it is doing them randomly.
12-04-2014, 08:02 AM   #12
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QuoteOriginally posted by sran Quote
Is there anything that could be done to improve it? Anything that would make it back focus always or front focus always. Currently it is doing them randomly.
Blasting the area with light during focusing could help. For instance, the focus assist LED on the new 540ii and 360ii speedlights pretty much nukes the area in front of it with LED light. This should make focusing accurate and fast in low light (focusing within 5m or so). But to my knowledge, the focus sensors on the K-5 were not sensitive enough in low light. Its more of a hardware problem that can't really be fixed without upgrading the body. The K-5ii has one newer f/2.8 sensor in the center, and the K-3 has three of them making wide apertures more accurate and allowing focusing in darker conditions.
12-10-2014, 08:59 AM   #13
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A few months ago I upgraded from the K20D to the K3, and the thing that impressed me most was the low light AF speed and accuracy (which I had occasionally found problematic with the K20D). With the 16-50/2.8 DA*, and also a Sigma 17-70 2.8/4 DC Macro, it mould nail focus at light levels in which I could barely see well enough to compose (focus checked by maximum zoom on LCD). Half the time it didn't even seem to bother with the AF assist lamp!

I feel my upgrade was worth it just for that!
12-10-2014, 09:08 AM   #14
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I have all three cameras, k-5IIs is already a big improvement in low light....but k-3 surpass k-5IIs by another step. As for accuracy, each camera is set to a default with some tolerance, and need to be checked to ensure there is no BF or FF issue in AF fine adjustment setting.
12-10-2014, 09:16 AM   #15
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Recently shot a group photo in a dark restaurant given these conditions: F2.8, 1/6s, ISO 12,800. Focus was spot on, and locked with just one try. Those values are equal to -1EV, which is around where a k-5 would fail.

The restaurant didn't have much lighting, most of the lighting came from wall scones and candles on the tables. Everyone was surprised that I didn't bother using flash (I don't like using flash, or the focus assist light).
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