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10-13-2019, 07:26 AM   #1
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AF performance with K-50 and SMC-FA 50 mm/f1.7

Recently I had to test my K-50 with an FA 50/f 1.7 in rather dark conditions (sparely illuminated room) with dancing/fast-moving people. Here I noticed an interesting behavior of the AF: The camera had major problems of finding something to lock on (while using the full reach of the adjustment length of the objective), but as soon as it found something, it could lock onto it even if the light got worse.

Thus, I assume that the initial lock-on is the most important part. Is there something I can do for making it easier for the camera to aquire that lock-on?

10-13-2019, 07:54 AM - 1 Like   #2
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It seems to me that contrast is the deciding factor, in low light the lack of contrast is what makes the focus struggle. Finding something with the best contrast should give the camera the best chance to lock on.
10-13-2019, 08:26 AM   #3
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Try a Zebra disco ?

10-13-2019, 09:02 AM   #4
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In dark conditions it is likely that many cameras will struggle with focusing. When you talk about locking, you mean in continuous AF mode?

10-13-2019, 12:44 PM   #5
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I assume you have the focus assist light on, if not enable it.
10-13-2019, 02:18 PM   #6
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QuoteOriginally posted by ramseybuckeye Quote
I assume you have the focus assist light on, if not enable it.
...and take care to not block it with one's hand.


Steve

(...been there, done that...)
10-13-2019, 11:44 PM   #7
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QuoteOriginally posted by sergysergy Quote
In dark conditions it is likely that many cameras will struggle with focusing. When you talk about locking, you mean in continuous AF mode?
Not necessarily, also in AF-S. The camera has no problems finding a good focus again after a sufficient focus was aquired, but as soon as I move to another object, it has to do the full aquisition procedure again.

---------- Post added 10-13-19 at 11:45 PM ----------

QuoteOriginally posted by ramseybuckeye Quote
I assume you have the focus assist light on, if not enable it.
I tried to avoid that, to not to disturb the people too much.
10-15-2019, 09:36 AM   #8
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QuoteOriginally posted by abraxas Quote
Not necessarily, also in AF-S. The camera has no problems finding a good focus again after a sufficient focus was aquired, but as soon as I move to another object, it has to do the full aquisition procedure again.
You did not indicate but can you confirm you are using the optical viewfinder, rather than live view? The K-50 has a slightly older auto-focus system (SAFOX IX), which is not as good in low light as the later models. You may want to try switching to just the single point center spot focusing mode, so you can point the camera at a specific subject to lock focus.

10-15-2019, 10:18 AM   #9
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QuoteOriginally posted by reduno Quote
The K-50 has a slightly older auto-focus system (SAFOX IX), which is not as good in low light as the later models.
This ^ ^ ^ ^


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10-16-2019, 02:02 AM   #10
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QuoteOriginally posted by reduno Quote
You did not indicate but can you confirm you are using the optical viewfinder, rather than live view? The K-50 has a slightly older auto-focus system (SAFOX IX), which is not as good in low light as the later models. You may want to try switching to just the single point center spot focusing mode, so you can point the camera at a specific subject to lock focus.
Did that, with mixed results. Still, the most surprising result was the fact that it could track objects even when it got darker, but could not reaquire focus on brighter subjects again until it found something useful.
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