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11-29-2008, 10:37 PM   #1
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Autofocus? Why is it so slow?

Hi folks,

I recently picked up photography as a side hobby. I purchased a GX-1L, the Samsung branded *ist D about a year ago. I knew about the big two at the time, and that buying a body meant buying into the whole system. Either way, I ended up with a Pentax (well, Samsung), and it has been very well to me thus far.

However, recently, I have had a chance to actually try out my buddies' camera, namely being the D80 by Nikon and a Canon XTi. I was blown away by how fast the auto focus was! I had heard that AF was not Pentax's strong point, but just last night, toying with the XTi in low light room settings on his stock lens, gave nearly instantaneous AF speeds. Compared with my GX-1L with the 1.4/50mm (supposedly one of Pentax's fastest lens), it was a wait period of nearly two or more seconds, depending on the subject.

I know my class of camera is the lowest of even the consumer line, so I'd like to ask if would an upgrade to a k100d or k10d would grant me similar focus speeds, as they have more (11, i think) focus areas compared to the *ist D's five. But then, I thought, doesn't it depend more on the lens than the camera body itself? Or is that only true for Nikon/Canon lens??

I know shake reduction is definitely a plus if I do decide to upgrade, however if I up to the k10d I'm be dismayed at loosing the ability to use AA's! Anyhow, I'll probably learn to suck it up in a few weeks when I received a batch of MF lens (one Jupiter-9, might I add) that is on the way. But I really wish I had that fast AF ability (especially low light) that can actually be compared to Canon/Nikon.

Lastly, I even considered switching to Nikon (is talk of that blasphemy here? ) for that AF speed. Is there anything I've overlooked?

11-29-2008, 11:20 PM   #2
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My first question is what type of batteries are you using?

For a long time I used to use NiMH rechargables in my K100... I now use Lithium AAs, and I'll never go back. The autofocus is noticably faster. Is it as fast as an equivalent Canon or Nikon in poor light?

No, probably not, but it's not slow enough for me to call it a negative. As for the K10, I can't comment, but the K20 definitely focusses slightly faster than the K100.

Also, I should add that in poor light, the AF assist from an AF360 or AF540 flash works wonders.
11-30-2008, 01:49 AM   #3
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Original Poster
QuoteOriginally posted by cpopham Quote
My first question is what type of batteries are you using?

For a long time I used to use NiMH rechargables in my K100... I now use Lithium AAs, and I'll never go back. The autofocus is noticably faster. Is it as fast as an equivalent Canon or Nikon in poor light?

No, probably not, but it's not slow enough for me to call it a negative. As for the K10, I can't comment, but the K20 definitely focusses slightly faster than the K100.

Also, I should add that in poor light, the AF assist from an AF360 or AF540 flash works wonders.
I'm using Eneloops, I'll definitely look into Lithium AAs, what do you suggest? I'll also have to see if I can try out the K10d or K20d first hand to get an idea of the AF speed.

Thanks for the reply.
11-30-2008, 02:05 AM   #4
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I can't speak for Eneloops - I used to use Energizer 2500 mAh rechargables. What I do know is this - the very best NiMH battery is 1.2V, and Lithium AAs are 1.5V. When you add this up in a full set of batteries, it's quite a lot less voltage...

As far as Lithium AAs go, I've found Energizer e2 Ultimate batteries work pretty well.

One thing to consider if you're trying to compare the AF on two cameras - make sure you're testing at around the same depth of field. The FA 50, for example, will have a very narrow DOF, compared to, for example, a normal kit type zoom at f3.5, or f4.5 - this means that while the camera has more light available to focus, it also has to focus more precisely.

11-30-2008, 06:58 AM   #5
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In addition to what has already been said, the FA50/1.4 is one of the slowest-focusing Pentax lenses. It is the "fastest" in terms of aperture only (i.e. f/1.4).

That being said, your camera will never AF as fast as the D80 or XTi, especially as the light level dims. The Nikon and Canon are more recent cameras, and as you heard, AF performance is not Pentax's strong point.
11-30-2008, 07:25 AM   #6
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QuoteOriginally posted by systemA Quote
Hi folks,

I recently picked up photography as a side hobby. I purchased a GX-1L, the Samsung branded *ist D about a year ago. I knew about the big two at the time, and that buying a body meant buying into the whole system. Either way, I ended up with a Pentax (well, Samsung), and it has been very well to me thus far.

However, recently, I have had a chance to actually try out my buddies' camera, namely being the D80 by Nikon and a Canon XTi. I was blown away by how fast the auto focus was! I had heard that AF was not Pentax's strong point, but just last night, toying with the XTi in low light room settings on his stock lens, gave nearly instantaneous AF speeds. Compared with my GX-1L with the 1.4/50mm (supposedly one of Pentax's fastest lens), it was a wait period of nearly two or more seconds, depending on the subject.

I know my class of camera is the lowest of even the consumer line, so I'd like to ask if would an upgrade to a k100d or k10d would grant me similar focus speeds, as they have more (11, i think) focus areas compared to the *ist D's five. But then, I thought, doesn't it depend more on the lens than the camera body itself? Or is that only true for Nikon/Canon lens??

I know shake reduction is definitely a plus if I do decide to upgrade, however if I up to the k10d I'm be dismayed at loosing the ability to use AA's! Anyhow, I'll probably learn to suck it up in a few weeks when I received a batch of MF lens (one Jupiter-9, might I add) that is on the way. But I really wish I had that fast AF ability (especially low light) that can actually be compared to Canon/Nikon.

Lastly, I even considered switching to Nikon (is talk of that blasphemy here? ) for that AF speed. Is there anything I've overlooked?
You've overlooked that Pentax AF is the slowest of all the camera manufacturers.
If you need really fast AF, look elsewhere, though do look at the K20 first, just in case it is fast enough.
11-30-2008, 07:42 AM   #7
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If you really want to shoot in an environment that requires fast acurate focus you need to switch to a diferent brand like Nikon or Canon as the K10D is just as slow as a glacier melting in winter :0) Don't get me wrong here. I love my camera and have learned to work with this disability as best I can but when your in the woods and a Great Horned Owl is flying right at you it can be a very frustrating experience to end up with so many poorly focused shots.
Kenn
11-30-2008, 07:53 AM   #8
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QuoteOriginally posted by Wheatfield Quote
You've overlooked that Pentax AF is the slowest of all the camera manufacturers.
If you need really fast AF, look elsewhere, though do look at the K20 first, just in case it is fast enough.
AF is instantaneous with K20d with the 21 and the 70, slow with the 35/2.8 (presumably because of the macro mechanism's bulk). I don't use zooms, but I suspect the-cheaper-the-faster because of the lightweight plastics.

11-30-2008, 08:24 AM   #9
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QuoteOriginally posted by systemA Quote
I recently picked up photography as a side hobby. I purchased a GX-1L, the Samsung branded *ist D about a year ago. I knew about the big two at the time, and that buying a body meant buying into the whole system. Either way, I ended up with a Pentax (well, Samsung), and it has been very well to me thus far.

However, recently, I have had a chance to actually try out my buddies' camera, namely being the D80 by Nikon and a Canon XTi. I was blown away by how fast the auto focus was! I had heard that AF was not Pentax's strong point, but just last night, toying with the XTi in low light room settings on his stock lens, gave nearly instantaneous AF speeds. Compared with my GX-1L with the 1.4/50mm (supposedly one of Pentax's fastest lens), it was a wait period of nearly two or more seconds, depending on the subject.
The GX-1L is simply old. Its AF-system is noticeably slower, than current Pentax modell's. Also, it is really slower than Canon/Nikon. Battery voltage might be a contributing factor, too.

If, on the other hand, the camera served you well so far, AF might be not the most important single decision point for you.

QuoteOriginally posted by systemA Quote
I know my class of camera is the lowest of even the consumer line, so I'd like to ask if would an upgrade to a k100d or k10d would grant me similar focus speeds, as they have more (11, i think) focus areas compared to the *ist D's five. But then, I thought, doesn't it depend more on the lens than the camera body itself? Or is that only true for Nikon/Canon lens??
AF speed depends on the camera body as much as on the lens. The Pentax SAFOX system has been improved over the years and the K10 and K20 AF-systems are much faster, than the istDx series (I had a istDS). With some lenses, AF might be faster or slower, but you will find, that the K10/K20 simply focus faster, because they have (to my knowledge) more powerful AF-motors inside. This is ofcourse not a topic if you use the new SDM lenses, which have the motor inside the lens.

QuoteOriginally posted by systemA Quote
I know shake reduction is definitely a plus if I do decide to upgrade, however if I up to the k10d I'm be dismayed at loosing the ability to use AA's! Anyhow, I'll probably learn to suck it up in a few weeks when I received a batch of MF lens (one Jupiter-9, might I add) that is on the way. But I really wish I had that fast AF ability (especially low light) that can actually be compared to Canon/Nikon.
You will find the battery life of the K10's special batteries so much better, than AAs, that you will not look back. The LiIon battery are small and lightweight and you can always carry a backup easily. It is much better, than AAs - that is at least my experience.

AF speed is still not as fast as Canon or Nikon, but very useable in most situations. Further to that, the Pentax AF is very reliable.

QuoteOriginally posted by systemA Quote
Lastly, I even considered switching to Nikon (is talk of that blasphemy here? ) for that AF speed. Is there anything I've overlooked?
If AF-speed is your one most important buying factor, because you need the fastest AF, than you should switch to Canon. If it is only one of the additional points, with things like image quality, handling and lens quality being more important, you should think about upgrading the a K10/K200/K20 or other current Pentax modell.

regards
Ben
11-30-2008, 09:39 AM   #10
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I believe the D80 has a focus-assist lamp built in to the camera, which helps it focus faster in low light. I think the XTi is more like the Pentax cameras, using the flash as a focus-assist. With Pentax, that only happens if you've still got your flash in "auto popup" mode, but I imagine most people probably turn that off, so you're not getting that. Not sure if your Canon friend had also turned off his focus assist, but if not, and his flash popped up to assist the focusing, that would explain most of the discrepancy right there. With no focus assist, the low light focusing would be more like the good light focusing - which is to say, Penax a little slower, but the difference would be nothing to write home about.
11-30-2008, 10:35 AM   #11
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QuoteOriginally posted by RBellavance Quote
That being said, your camera will never AF as fast as the D80 or XTi, especially as the light level dims. The Nikon and Canon are more recent cameras, and as you heard, AF performance is not Pentax's strong point.
I think this is partially myth. Pentax's autofocus is very weak at tracking moving objects, particularly ones moving towards you. However, it isn't really a slouch overall. Based on hands-on experience, my K10D with the DA 40mm f/2.8 Limited is astoundingly faster than my friend's Canon 10D with Canon's 50mm f/1.4 in low light, and still better than his 30D with the same lens and conditions. I'm sure the 40D is improved some, but the point is it's not like Pentax is out of the game. And several tests have demonstrated that it's slower but more accurate than the competition in low light.

I think mostly the tracking issue has contributed to a "Pentax AF = slow" meme which is hard to shake.
11-30-2008, 12:36 PM   #12
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QuoteOriginally posted by systemA Quote
GX-1L, the Samsung branded *ist D
However, recently, I have had a chance to actually try out my buddies' camera, namely being the D80 by Nikon and a Canon XTi. I was blown away by how fast the auto focus was! I had heard that AF was not Pentax's strong point, but just last night, toying with the XTi in low light room settings on his stock lens, gave nearly instantaneous AF speeds. Compared with my GX-1L with the 1.4/50mm (supposedly one of Pentax's fastest lens), it was a wait period of nearly two or more seconds, depending on the subject.
According to Popular Photography - there was a good improvement in AF speed at about the K100D -

" More noticeable was the K100D's improved AF performance across the board, and especially in very low light—possibly another benefit of the improved processor in the K100D. Even in very bright light of EV 12–8, the K100D showed a 0.2 sec improvement over the AF on the *ist DS2, which it maintained all the way down to EV 2. At EV 1 and EV 0 there was a dramatic improvement to 1.51–1.81 sec compared with 1.71–2.2 sec on the *ist DS2. Best news? The K100D now focuses down to EV –1, although rather sluggishly in 2.5 sec. "

Here are the respective AF speeds from the PopPhoto tests -
Pentax K100D at PopPhoto
Nikon D80 at PopPhoto
Pentax K20D at PopPhoto



Pentax K10D were tested at:
AF Speed
EV 11_EV 10_EV 8_EV 6_ EV 4_EV 2_EV 1_EV 0_ EV -1
0.37 _ 0.44 _0.43_0.54_0.97_1.17_1.22_1.67_2.33
(note the horiziontal (light level) axis/scale on the K20D chart is misaligned - it should be the same as the other 2 charts)

One can see that the Nikon D80 is faster when the light level drops below about +4EV whereas surpisingly the K20D is faster at bright light levels.

I use the K100D a lot for music concert photography - although it is not really low light (stage lights are bright) I am often dealing with marginal handholdablity - so that means ISO1600 @ about 1/15th sec probably around f/4 - (that's the equivalent to ISO100 f/4 at 1sec) = +4EV right on the margin of AF starting to be slow - taking about 1 sec to focus.

Using the PopPhoto charts the K20D would also take about 1 sec - whereas the Nikon D80 would take 0.6 sec - faster but not that much......

I can't find the Canon XTi PopPhoto review - but this is what they said in a comparison shootout about the XTi -
" Autofocus was equal in sensitivity to the Nikon D80, and at least as fast as the Nikon at all light levels. Only the Sony's AF was faster, and only at EV -1 to 3. "

Obviously as others have pointed out AF speed is also dependent on the lens used.

see also this recent thread - Focusing speed comparison K200D vs. K20D

However it is my habit to pre-focus - so although "slow" might seem frustrating - I don't miss that many shots, since when I actually shoot - the camera is already pre-focussed and the only lag is the actual shutter lag (after pre-focus) which is in the ballpark of about 0.1 sec - faster than any AF.

Last edited by UnknownVT; 11-30-2008 at 12:59 PM.
11-30-2008, 02:10 PM   #13
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QuoteOriginally posted by mattdm Quote
I think this is partially myth. Pentax's autofocus is very weak at tracking moving objects, particularly ones moving towards you. However, it isn't really a slouch overall. Based on hands-on experience, my K10D with the DA 40mm f/2.8 Limited is astoundingly faster than my friend's Canon 10D with Canon's 50mm f/1.4 in low light, and still better than his 30D with the same lens and conditions. I'm sure the 40D is improved some, but the point is it's not like Pentax is out of the game. And several tests have demonstrated that it's slower but more accurate than the competition in low light.

I think mostly the tracking issue has contributed to a "Pentax AF = slow" meme which is hard to shake.
Good point. Poor AF performance was the argument why I didn't first didn't consider Pentax when buying my first own DSLR. I used Canon and Nikon on several occasions, but luckily enough my local store convinced me to try Pentax for a weekend before making up my mind. It is true that tracking mode on the K20 was a real disappointment compared to what I knew from other brands, but I was really surprised at the good and reliable AF behaviour overall. So if action and sport shootings are not your daily occupation, then upgrading to a newer Pentax model might be a satisfying solution.
11-30-2008, 02:17 PM   #14
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QuoteOriginally posted by systemA Quote
...Anyhow, I'll probably learn to suck it up in a few weeks when I received a batch of MF lens (one Jupiter-9, might I add) that is on the way. But I really wish I had that fast AF ability (especially low light) that can actually be compared to Canon/Nikon.
I guess you said a mouthful here. A couple of points:
  • Relevance of AF with your new MF lenses
  • How well your MF glass would work on either Canon or Nikon.

As noted in a couple of posts above, you really have to ask yourself how important AF is to your style of photography. If it is paramount (you do sports or wildlife), then you might be with the wrong system.

One last thing...Be sure that the other systems are really faster and/or more accurate. As I noted on another thread about two month ago, I was doing some landscape shots at a popular viewpoint near my home and a fellow with a mid-range Canon (40D, I think) walked up next to me to take a couple of shots. Now it was about 1/2 hour before sunset and a little hazy, but he tried for about a minute to acquire focus and finally switched to manual. Meanwhile, I continued to shoot with my K10D with no problems whatsoever. We were both shooting the same subject at about 200 yards distance with the rest of the scene at infinity. Maybe it was a difficult subject for the Canon system, but to be honest, it was just the classic tourist snapshot in full daylight. It was about that time that I figured that while there are advantages to the different AF systems, none are perfect.

Steve
11-30-2008, 02:41 PM   #15
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A few more quotes, this time from DPReview:

RE: K20D...
QuoteQuote:
...The autofocus, while never breathtakingly fast, is also never intrusively slow for general shooting. Using enthusiast-level lenses (16-45mm f/4 or 35mm f/2.8 Macro), its performance, even in low light, has been at least comparable with similarly-priced cameras, if not quite up to the standards of the more expensive, similarly-specified cameras from other brands...
RE: K10D...
QuoteQuote:
...Accurate and fast auto-focus...
Steve

Note: These review comments should be taken in light of the technology at the time of review (when each camera was released).
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