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11-02-2010, 07:30 AM   #1
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Question - K5 Low Light AF

I am curious if any of the new K-5 users can comment on low light AF with a fast lens wide open ( say 1.4/1.8 ) in bad lighting conditions.

I am trying to get an idea on the AF accuracy/speed when lighting is poor, and the user wants to push the ISO up to say 6,400 and must use the glass wide open.

Anyone care to share their experience? Is the AF accurate enough to focus wide open in low light conditions and nail focus, say on the subjects eye without front/back fous? Does the AF hesitate much?

I am curious, when I had a K20D, I found the AF with my 70mm DA would hesitate a lot in low light, and usually failed to lock focus, usually around 1600 ISO with 1/100 speed, wide open.

Any input would be great. Thanks

11-02-2010, 08:37 AM   #2
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It's not lightning fast, but it is very accurate. I haven't had my K-5 hunt yet, even when most the lights were off in the house. You just point it at what you want and it'll do it's thing. It gets close to being focus, then fires another burst of the assist light and fine-adjusts the focus one more time- then bam, it's locked! With the K-5, I'm under the impression that the assist light actually does something, and that wasn't so much the case with the K-7

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11-02-2010, 10:21 AM   #3
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Let's hear more. This is a very important question if you are supposed to be able to take advantage of the high ISO capabilities.
11-02-2010, 10:24 AM   #4
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I was able to use AF successfully (w/ the AF assist lamp) in conditions three stops below what the in-body light meter was even able to register (- 3 EV; f/2.8, 1/8s, ISO 51200). No question the low light AF abilities of the K5 are a few steps above the K20D,

11-02-2010, 12:41 PM   #5
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За мен също това е много важен въпрос!
Аз снимам репортаж ,концерт и танци при малко светлина и с К-20 имам проблеми при АФ.
Как е АФ при малка светлина в К-5?
Поздрав!
11-02-2010, 02:01 PM   #6
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This is something which I had asked before, in many threads:

Can we get some sample AF shots (specifically AF-C) at high ISO under less-than-ideal lighting conditions?

Quoting Adam: "It's not lightning fast, but it is very accurate.", this leads me to believe that the K5 can actually handle this sort of situation.
For those who like Christmas pics taken under such "less-than-ideal" lighting, I think they'll be happy.

Adam: have you used any particularly "fine" glass this far? It would be interesting to find out if one specific lens would produce better results over another one, under poor lighting conditions.

Cheers.

JP
11-04-2010, 02:47 AM   #7
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I'll try to do some real low light AF tests at home when I have some free time. Yesterday I had some time for quick playing with K-5, I recall taking a few photos at ISO3200 f1.4 1/15s and AF didn't hunt, focus was ok.
11-04-2010, 10:46 AM   #8
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That would be great!

11-04-2010, 11:49 AM   #9
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Sorry, I didn't have much time to make anything scientific or interesting, too tired and hungry for that. So only a quick snap in the living room, lit only by the TV screen. It was pretty dark, I could barely see the bear in the viewfinder, focused on his tie. AF assist light turned off, camera locked focus without hunting and reasonably quick in my opinion.

ISO6400, F1.6, 1/20s (out of camera JPG with NR off by the way)
Direct link to full size pic.

Last edited by simico; 11-04-2010 at 11:56 AM.
11-04-2010, 06:43 PM   #10
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QuoteOriginally posted by simico Quote
Sorry, I didn't have much time to make anything scientific or interesting, too tired and hungry for that. So only a quick snap in the living room, lit only by the TV screen. It was pretty dark, I could barely see the bear in the viewfinder, focused on his tie. AF assist light turned off, camera locked focus without hunting and reasonably quick in my opinion.

ISO6400, F1.6, 1/20s (out of camera JPG with NR off by the way)
Direct link to full size pic.
Yes!!
This is just so great!

Jpeg straight out of the cam, wide open, low shutter speed, and NR off ... way to go, Simico! Oh, and I just realized that you had the AF assist light off too.

I don't usually shoot JPEG (RAW almost all of the time) but this is actually very good and it might even convince me to start doing some JPEG's test shots as soon as the K5 arrives.

By the way, what lens did you use?

Cheers.

JP
11-05-2010, 02:44 AM   #11
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QuoteOriginally posted by jpzk Quote
Jpeg straight out of the cam, wide open, low shutter speed, and NR off ... way to go, Simico!
Thanks! Actually I was wrong on the NR, just noticed that NR is at factory default med setting for ISO6400 - I turned off NR for all other ISO values, seems like somehow I missed this one.

I'm also a RAW shooter, but my raw developer app doesn't support K-5 yet (will send them lots of PEF and DNG this weekend), so at the moment I shoot in RAW+ mode and just use the jpegs.

Lens was Sigma 30mm f/1.4. Pic should have EXIF intact.

Hopefully I'll have some time to play with K-5 at the weekend, work really exhausts me on workdays and taking care of my little daughter takes up almost all of my free time in the evening.
11-05-2010, 03:19 AM   #12
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(Yay! First post.)

Bought a K5 yesterday. I'm starting to think it's defect because I also have a Sigma 30 1.4 and focusing in low light was terrible when I tested it yesterday evening. It also underexposed by 2-3 stops in low light. In liveview exposure was much better. Am I doing something wrong? Any ideas? I'm new to Pentax.
11-05-2010, 03:34 AM   #13
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QuoteOriginally posted by simico Quote
Sorry, I didn't have much time to make anything scientific or interesting, too tired and hungry for that. So only a quick snap in the living room, lit only by the TV screen. It was pretty dark, I could barely see the bear in the viewfinder, focused on his tie. AF assist light turned off, camera locked focus without hunting and reasonably quick in my opinion.

ISO6400, F1.6, 1/20s (out of camera JPG with NR off by the way)
Direct link to full size pic.
Thanks for what's the one useful answer in this thread.

EV is 0 and considering the image is underexposed by about one stop, lighting may have been -1 EV.

As you can read here in my blog, the K-7's limiting lighting was about 0.5 EV with a good contrast target. So, the K-5 AF seems to be improved by 1-2 stops or better.
11-05-2010, 09:20 AM   #14
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QuoteOriginally posted by simico Quote
Thanks! Actually I was wrong on the NR, just noticed that NR is at factory default med setting for ISO6400 - I turned off NR for all other ISO values, seems like somehow I missed this one.

I'm also a RAW shooter, but my raw developer app doesn't support K-5 yet (will send them lots of PEF and DNG this weekend), so at the moment I shoot in RAW+ mode and just use the jpegs.

Lens was Sigma 30mm f/1.4. Pic should have EXIF intact.

Hopefully I'll have some time to play with K-5 at the weekend, work really exhausts me on workdays and taking care of my little daughter takes up almost all of my free time in the evening.
Still, not bad at all!
By the way, why don't you use the Pentax Camera Utilities, provided on CD, with your camera when you bought it?
I have been using this RAW "converter" ever since I owned a K10D, then a K20D and now a K7, with good results.
I am told that the latest version is quite stable and efficient (v. 4.31?).

Sorry I missed on the lens via the EXIF data; this Sigma seems like a great lens and according to the reviews, great IQ.

Take it easy over the weekend .... health and family come first!

Cheers.

JP
11-29-2010, 04:08 AM   #15
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Hi all,
I took my k-5 to a birthdayparty with low light conditions. You could compare the light levels to a cozy restaurant at night.

My experience of the AF was horrible..
I used two different lenses: Pentax DA 16-50 and Pentax DA 50-135.

The Af got it right in about 40% of the shots. Sometimes it even indicated aqquired focus but the focus was totally off and blurry.

I tried both manual and fully auto "green mode".
I noticed a quite big improvement in AF accuracy if not using live view, but far from acceptable.

One really annoying thing was that with the lens hood on the 50-135, the AF-assist light was obscured and AF didn't work. This was also a problem with the 16-50, but not as big.

I had to use the lens hood as "protection" from childrens fingers.

Maybe I have a faulty K-5?
I will do some more tests as soon as i get some time.

Regards

RB
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