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08-09-2010, 06:18 PM   #1
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Question about focus speed and focusing on Pentax vs others

Hi guys, I'm new to DSLRs and the Pentax Kx is my first dslr. Up until now, I've stayed with bridge cameras like the Canon G9 and the Lumix LX3.

There's quite a few camera hobbyists here in the office, but I'm the sole Pentax owner. The rest have a Canon 50D, Canon 550D, and 1 Nikon D90. I've never been a brand person at all, and I didn't choose Pentax because I like its underdog status or such. I wasn't even thinking of getting a Pentax, but when I walked around in the store and actually holding each camera in my hand, the Kx and the K7 just felt so right in my hands. That pretty much sold it for me.

That being said, when we all brought our cams into the office to have a bit of fun, we all noticed that the Pentax seemed to have both the slowest autofocus out of the bunch and also missed focus a lot more often. Kind of a bummer, since I wanted to do Pentax proud. Just to note, it was with the Kx and the FA77 and also the DA35 Macro.

Am I just doing something wrong or is the AF just not up to par compared to Canon/Nikon? In a way, is lackluster AF being just a price to pay for all the other benefits we get with Pentax, like great primes, great ergonomics, etc?


Last edited by uchinakuri; 08-09-2010 at 06:27 PM.
08-09-2010, 06:45 PM   #2
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Unfortunately, Pentax AF just plain isn't quite as good as the competition.
However, their lenses are better, so it's a compromise that I am willing to live with.
08-09-2010, 06:47 PM   #3
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First welcome to the forum. Like you, I bought a Pentax because it felt right in my hands and the small size was an asset.

The K-x is an entry dSLR, and the comparison with the D90 or 50D (both semi-pro dSLRs) is not really fair. You need to compare apples and apples.

Second I may suggest to check that you have the latest firmware in your K-x. Pentax made some significant improvements in the latest firmwares (both K-x and K-7) and you do not want to miss these.

In terms of AF, what setup do you have? Many Pentaxians suggest to use center-focus and AF.S. This is my basic setup and it is quite fast.

Hope that the comment will help...
08-09-2010, 06:55 PM   #4
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pentax autofocus is slow. but focus confirmation works just fine.
if you can take a fraction of a second slow autofocus and not so great flash performance, everything else compares/works better with comparable cameras of other brand.

08-09-2010, 06:55 PM   #5
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Pentax is known for its slow AF system, which is why you do not see them on the sidelines at sporting events. They are still capable cameras, so don't let your Canikon friends tell you any different, and don't worry about it.
08-09-2010, 07:01 PM   #6
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Thanks for all the comments, guys. Just to note, the canon/nikon guys weren't putting Pentax down, we were all just collectively trying to learn stuff together. I figured that the 50D and D90 are a notch above the Kx, but the 550D is Canon's entry level. The 550D AF was clearly faster than the Kx...

I mostly use center-focus (and recompose) and AF.S as you mentioned...also, I checked for new firmware back in July, so I *think* I'm up to date! I'll have a check again tonight though!
08-09-2010, 08:03 PM   #7
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It's worth noting that you had two of the slooooowest AF lenses in the Pentax lineup...
08-09-2010, 08:45 PM   #8
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Lenses do make a big difference. My Sigma 50, 105 and Pentax DA 40 lenses seem to lock in fast while my DA55-300mm feels much slower (primes vs zoom). I was in a store one day playing with a D50 and could not believe how fast the AF was. I still would not give up my K-X though. Quite a few other features that make it the right camera for me.

08-09-2010, 08:53 PM   #9
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Don't lose heart.
AF speed is not everything (unless you're talking sports/action photography all day long).
As long as it does hit the focus reasonably quickly and accurately, you should get results that at least match those of your counterparts.

The FA 77 and DA 35, although having such long focus throws and thus slow AF, produce the sharpest and brilliant images around.
08-10-2010, 08:53 PM   #10
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I rather doubt your experiment was sufficiently well-controlled to allow you to draw conclusions about the camera "missing" focus - most cases of missed focus are user error (not specifiying a focus point, or trying to focus on a subject smaller than the range covered by the focus sensor).
08-14-2010, 10:46 PM   #11
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I've actually had some good successes with my K20D and various lenses when using the AF.C setting. Mind you, I've been outdoors with reasonably bright light. But I'll admit that I didn't put much faith into what would happen the first time I was going to try this because of what I had read on this forum. But after I tried I was very impressed, perhaps because my expectations were low in the first place. In other words, nearly every frame of action was tack-sharp. But mind you a person with not much experience with their SLR could expect the same.

As for indoors with dim lighting, that's what quick-shift focus is for. If AF doesn't nail the focus, then I just give that focus ring a little twist (if your lens has quick-shift) and look for the in-focus indicator in the viewfinder. I've found it to be pretty accurate as well. If my lens doesn't have quick-shift and the AF is giving me grief, I switch to MF, look again for the in-focus indicator, and hope for the best.

There's always a work-around, and practice ultimately will nail the focus more accurately with time.
08-14-2010, 11:08 PM   #12
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One trick I recently found on the K-x that really helps
when the autofocus constantly hunts and won't let you take your pic.
(especialy in difficult low-light, low contrast conditions)

You can set the AF / AE-L button to disable the autofocus,
so as soon as your confident that your subject is in focus,
press the button, the MF icon appears in the viewfinder,
and you don't loose your focus in between pics.

And yes the lens does make a difference,
my newly aquired Sigma 24-70mm f2.8 (non-HSM)
focuses faster than my similar Sigma 18-50mm f2.8

Last edited by mlatour; 08-14-2010 at 11:14 PM.
08-15-2010, 04:08 AM   #13
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If you have your kit lens, put it back on and try focus speed with it versus your primes. You will find that it is significantly faster. As fast as Canon/Nikon? I have no idea, but in decent light you probably wouldn't notice a difference. You are mainly seeing lens effects. The Da 35 in particular, but also the FA Limiteds tend to be a lot slower. The rest of the DA limiteds are pretty spry auto focus performers, but the fact that the DA 35 is a macro lens can really slow it down at times.
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