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11-05-2010, 09:56 AM   #1
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K-x Autofocus speed

Hi

I am evaluating buying k-x or trying to get a good deal on t2i.

I am sold on k-x and think that for $600 with two good lens 18-50 and 50-300 that it would be everything I need.

My only concern that I have read is that the autofocus on k-x is slow, that it takes 2-3 seconds to get it right. Also, that the 11-point focus does not have an indicator of where it is focused.

I am a begginner in the dslr world and have two small children. I don't mind using manual focus for the most part, but I am not sure if my wife will like to wait 2-3 seconds (which seems like forever when you have small children moving around and would not stand still).

Thoughts?

11-05-2010, 10:18 AM   #2
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The phase-detect AF (with the viewfinder) is pretty snappy actually. The 2-3s figure sounds more like the contrast based AF (with the LCD display) which is quite slow.

The k-x doesn't have the AF point indicators on the viewfinder. Personally, I don't really miss them much, mostly because using center point only and composing after locking focus gives more consistent results. When there is no time for that sort of thing I would suppose that there wouldn't be time for recomposing after seeing from the idicator points that focus has been locked to something else than intented. In a nutshell: nice to have, not essential.
11-05-2010, 10:47 AM   #3
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The AF speed on the K-x is probably better than you have heard.
2 to 3 seconds to get focus lock is not typical. If in doubt, try it out at a camera store somewhere.

You can choose various AF parameters with the K-x to tune the way the AF works - eg use spot AF metering, AFC to track moving targets etc. And the lack of illuminated AF points isn't anything you'll miss, especially if you prefer to use spot AF anyhow so that you always know exactly where the AF is working.

But no camera AF is magic. Like any feature of the camera, you have to learn how to get the best out of AF, just like you do with the exposure metering system, the shutter speed etc. If you have a room full of people and you want the camera to focus on one person in particular, the camera will have to be guided quite a lot by you to do that. It wouldn't be a fault of the camera if it focussed on Jim rather than Jane if you pointed it at Jim. It would also help if you made sure Jane wasn't sitting totally in the dark when you were hoping to get her in focus. And so on.

Often users also do other things that make things harder for the AF - eg put junk UV filters on their lenses that interfere with the brightness of the lense and the sensitivity of the AF. You'd want to avoid doing that.
11-05-2010, 10:52 AM   #4
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I used a Kx for about a year and took 15k shots with it (and a ton of them were pictures of my two kids), and the AF was plenty fast 99% of the time. It would be a very rare situation (with either very little light or a very low contrast target) that would cause the AF to take 2-3 seconds to lock with a Kx.

11-05-2010, 10:55 AM   #5
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I wish you would just go hold each camera in your hands before you deceide. The K-X feels like a pro camera the Canon t2i feels like a childs toy. I have a close friend that has one and when she handed it to me I couldn't believe how cheap it felt in my hands and it was awkward feeling also.
11-05-2010, 11:23 AM   #6
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QuoteOriginally posted by Fl_Gulfer Quote
I wish you would just go hold each camera in your hands before you deceide. The K-X feels like a pro camera the Canon t2i feels like a childs toy. I have a close friend that has one and when she handed it to me I couldn't believe how cheap it felt in my hands and it was awkward feeling also.

I tried doing this today, but Bestbuy did not carry in store the pentax and the canon was connected to their security system so the weight and feel were deceving.

Is t21 worth $200 or so more, is the question. I think picture wise they are on par, is the other stuff that I am evaluating. I do not think that 1080p makes much difference for me, but is the AF that is of a concern.
11-05-2010, 11:54 AM   #7
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i am in the exact same situation. i am worried about action shots with the kx, compared to a canon t1i. I suppose more of this depends on the lens, not the camera.

i am also wondering about the jpeg engine. i am coming from an Olympus slr. i have never taken shots in RAW, and would rather just use the camera's jpeg engine. How are the jpegs, straight out of the camera?
11-05-2010, 12:05 PM   #8
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You might want to read this: Pentax K-x Review: 1. Introduction: Digital Photography Review

executive summary: jpeg engine does a great job, no problem with AF speed

11-05-2010, 12:11 PM   #9
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" The K-x’s autofocus tested well, too, with very strong performance in brighter light. At EV 12 through EV 6, it was equal to or faster than the two competitors. Though its AF was slower than the Canon and Nikon in dimmer light, it remained within 0.6 seconds of them even at its worst"
Camera Test: Pentax K-x | Photography - PopPhoto.com Offers Camera Reviews and Exclusive Photo Tips

K-x


T1i:


K-x looks pretty bad here actually, heh, their non-AF numbers don't seem to match many experiences. My friend has a T2i but I much prefer my K-x. Does fine in sports for me (some pics in my flickr). I use AF more than him.

Last edited by Eruditass; 11-05-2010 at 12:35 PM.
11-05-2010, 05:15 PM   #10
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Depends on the lens. With the fabulous DA40 focus snaps into place like the crack of a whip.
11-05-2010, 07:06 PM   #11
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QuoteOriginally posted by keano016 Quote
Hi

My only concern that I have read is that the autofocus on k-x is slow, that it takes 2-3 seconds to get it right. Also, that the 11-point focus does not have an indicator of where it is focused.
I think you can safely conclude that if the K-x did typically take silly impractical times to lock in autofocus on a subject then the product would have been ridiculed off the market long ago.
You're right, your kids will have grown into teenagers in that time.

Yes it will "hunt", and my K-x certainly does in difficult light conditions or impossible focusing lengths, and esp with some lenses notorious for that, but what camera doesn't?

On the contrary, I find it amazingly fast actually, for a cheap-featured clunker using mostly in-body driven AF.

And naturally, when fitted with a lens such as a Sigma with HSM, it can be even faster and almost whisper quiet too.

K-x does have a when-focus-is-locked-in viewfinder indicator Btw, and as someone else pointed out the K-r has supposedly better.

If you can go the extra $$ I'd buy a K-r instead for extra goodies and if only because K-x is like reading last week's newspaper now.

.R.
11-06-2010, 12:01 AM   #12
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those with the k-x, would you consider the AF in low light bad?

I'm asking because I'm wondering how much the AF assist lamp in k-r will improve the low light AF over k-x..
11-06-2010, 12:08 AM   #13
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I've taken shots of my school dance in near pitch-dark and it locked on then admirably, and shooting a f5.6, it was more or less dead on accurate unless I was aiming the center point somewhere other than where I wanted it to be - I guess that's where illuminated af points would be pretty helpful. That said though, while it did lock accurately in those (horrible for AF) conditions, it sometimes did hunt or take several seconds. Do note however, that this was quite nearly pitch black and I could barely see with my own eyes, let alone through the viewfinder.

On the other hand, when I shot at a rock/metal concert, even in dark stage lighting (but I could see just fine) the AF never let me down.

Both of the above scenarios were shot with the DA40 ltd.
11-06-2010, 06:23 AM   #14
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QuoteOriginally posted by min.t Quote
those with the k-x, would you consider the AF in low light bad?

I'm asking because I'm wondering how much the AF assist lamp in k-r will improve the low light AF over k-x..
I've been happy with it. It seems that it keeps working until shutter times get inpractically slow for handheld shots. Then again I've mostly used it with people inside, there tends to be enough contrast for it. Also, I mostly use the Tamron 17-50 2.8 for these (or the M501.4, no AF with that), lens choice might affect this.

One thing to note here is that initial AF may take longer as the camera may end up going trough the entire focus range, but after that small fast adjustments usually work. I think the lens choice affects this in particular, the Tamron 17-50 2.8 is quite fast even for the initial AF, while the DA(L) 55-300 may take quite a bit of whirring around to find the adjustment. I suspect a lot of this is simply because of the much longer focus throw of the 55-300, then again it is not a low-light piece anyway.

The k-x can use the flash as an assist lamp (you just need to pop it up), but I haven't felt the need to use this, and would probably turn the k-r lamp off for the kind of shots referred to above so that I don't distract/annoy the people.
11-06-2010, 07:07 AM   #15
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its as fast as Nikon or Canon...in the same camera league. At some points I think the kx is faster than the Nikon d90...with the kit lenses on.
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