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12-10-2016, 02:52 PM   #1
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Autofocus in low light.

I'm really loving the K-1 and the autofocus is pretty darn good in good lighting conditions (tending to favor accuracy over speed which I like). I am however facing issues finding a way to auto-focus in lower light situations. This is really important for wedding photography and event photography (both things I do).

I started off my quest for good low light auto focus by renting the Amazon.com : Pentax AF540FGZ II Flash for Pentax DSLR Cameras : On Camera Shoe Mount Flashes : Camera & Photo. While the flash itself worked wonderfully, I found that under many circumstances the autofocus took .5 to 2 seconds to lock on. This was in sub-optimal lighting conditions but with people posing just a few feet in front of me, nothing that should be too difficult with an af assist beam. My intuition was that the af beam on the 540 wasn't that great, or that the camera itself was not turning the af assist beam on under circumstances when it thought it could manage. I did see the af assist beam come on from time to time but not always.

Suspecting that perhaps the 540 af beam wasnt that great I ended up purchasing the metz 52 af-1. I then found out that the af assist beam simply doesnt work in concert with the k-1. It's fully incompatible. This leaves me with the built in AF illuminator.

Comparing to my nikon d3100 plus the sb-700 (pretty basic flash) the difference is literally night and day (pun intended) and the nikon d3100 is a pretty basic camera.

I am concerned that there is simply something wrong with the k-1's algorithm for enabling the af assist beam ...

Has anyone else had better results than me and under what circumstances?

Thanks!

-Lars

[Update] - I always set the camera to spot focus (center spot) and use AF-S.


Last edited by larsbars; 12-10-2016 at 02:59 PM. Reason: Additional Information.
12-10-2016, 05:37 PM   #2
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I have a K-5 II and can confirm the camera is wildly overconfident in its low-light focusing abilities. While it does lock in almost total darkness, it takes its time doing so.

It would be great if there was a way to force the AF illuminator on.
12-10-2016, 05:39 PM   #3
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What lens are you using?

Without the AF beam I'd maybe try using more AF points. But I think you're right- the camera is a bit conservative on the assist light, since it's theoretically not as important as before the days of -3EV AF.

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12-10-2016, 07:37 PM   #4
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QuoteOriginally posted by larsbars Quote
I always set the camera to spot focus (center spot) and use AF-S.
To explore the AF illuminator behaviour further, try some tests using different 'AF active area' settings. Plus make sure you are setting the AE metering mode to 'Multi-segment' so that the camera is fully able to read the scene lighting, and properly make it's mind up about whether it's going to be important to turn the AF assist light on (or not).

I'd also do some tests setting the camera mode dial to 'Auto', and see how that works out.

PS - are you using any filters on your lens?

12-10-2016, 08:33 PM   #5
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Not using any filters and I'm using the 24-70 2.8 HD DFA. I'll try all those suggestions and report back. Thanks!
12-14-2016, 12:41 PM   #6
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QuoteOriginally posted by Adam Quote
But I think you're right- the camera is a bit conservative on the assist light, since it's theoretically not as important as before the days of -3EV AF.
Right.. it will be great if they add a Menu setting that can setup the assist light sensitivity to (low, mid, high), at fast focus situations having just the -3EV and not using the assint lamp might turn the focusing kind of slow.
12-14-2016, 04:43 PM   #7
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QuoteOriginally posted by kooks Quote
add a Menu setting that can setup the assist light sensitivity to (low, mid, high)
Combined with an option to simply turn the AF-assist light on 'on-demand' - ie every time auto-focus is active, or every time the shutter or AF button is half-pressed.

So the settings would look like:
AF Assist Light:
Off > low sensitivity > medium sensitivity > high sensitivity > On demand.
12-14-2016, 07:28 PM   #8
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QuoteOriginally posted by rawr Quote
Combined with an option to simply turn the AF-assist light on 'on-demand' - ie every time auto-focus is active, or every time the shutter or AF button is half-pressed.

So the settings would look like:
AF Assist Light:
Off > low sensitivity > medium sensitivity > high sensitivity > On demand.
I would really really appreciate this... does anybody know of any way to request something like this for a future firmware update? A perfect example of when this is needed is when shooting a wedding reception with bright DJ lights behind the subject.

12-14-2016, 10:21 PM   #9
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QuoteOriginally posted by jab2980 Quote
I would really really appreciate this... does anybody know of any way to request something like this for a future firmware update? A perfect example of when this is needed is when shooting a wedding reception with bright DJ lights behind the subject.
We'll be setting up a suggestions forum for Ricoh shortly. For now you can post the suggestion directly in the Ask Ricoh Imaging forum.

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12-14-2016, 11:22 PM   #10
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QuoteOriginally posted by jab2980 Quote
A perfect example of when this is needed is when shooting a wedding reception with bright DJ lights behind the subject.
Exactly.. at that same situation is when i most wish to have a feature like that..
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