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Forum: Troubleshooting and Beginner Help
04-04-2014, 04:32 PM
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Hi, I am not referring to the AF speed part of imaging resources test (which I agree does not give a full picture as its only one component of the real AF lag). The part I am referring from that website is more the "Prefocused lag", i.e. you first acquire focus, then you are waiting for something to happen (for example a face that is looking back to tunraround), and then the moment you perceive it in the viewfinder, you'll press the shutter button, and then there is a slight lag between the moment of pressing the button, and the shutter actually moving and taking the shot
Anyway as you mention the 1/20 s pre-focused lag difference will not matter to everyone, only for certain shooting style, but this lag (along with viewfinder blackout lag) is usually one of the features distinguishing performance oriented model and normal model (e.g. difference between 7D/70D and 700D, or nikon D7100 vs D3xxxx), and interestingly, actually an area modern mirrorless camera and performance compact sometimes outdo the DSLR (as they have no mirror to move, they can have a lag at the level of 10 -20 ms, though in return they have the EVF/LCD lag which adds around 30 ms, but its still very fast).
It's something pentax could improve for the next generation models.. but again look at all the goodies we have on Pentax - complete feature set, the great build/compact size, the great color rendering, the great image quality, and best of the class dynamic range (and far away from canon APS sensors in this regard), it's hard to not like it (and yes AF is getting better and better with each new model)
I think i'll always keep at least one pentax DSLR due to those aspect of pentax
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Forum: Troubleshooting and Beginner Help
04-04-2014, 07:40 AM
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you can try this website, in my opinion, they are very reliable when it comes to pre-focus AF speed as its easy to measure (but a bit miss leading when it comes to real AF speed measurement)... otherwise you can try the two camera side by side and 50 ms difference is more than noticeable if you are paying attention.
Pentax K-3 Review: Now Shooting! - Performance
Canon 70D Review - Performance
Nikon D7100 Review - Performance
But again, it depends a lot on the shooting style, if your shots are rarely pre-focused, this doesn't matter (it does for me, as majority of my shot is focused in advance, and i am just watching for a particular expression before i fire)
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Forum: Troubleshooting and Beginner Help
04-03-2014, 11:01 PM
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Hi Dan
i did not make any comment on tracking ability as I think that was not the subject of interest for Chris (and indeedI was considering to switch to K-3 precisely for the fact that it can properly track).
In fact, If you have a look at my earlier comments, i am basically trying to explain to Chris that under single-shot AF (not C-AF), the larger determining factor is the lens, not the body... and the lenses tend to be faster on canon bodies than pentax (by a fairly large margin) as he was surprised on old entry rebel could be faster than the latest flagship pentax model.
I'm a little surprised that there is a tendency of criticism between the different replies, everyone has their perspective based on their personal experience, and on slightly different scope (C-AF and S-AF is a totally different subejct) which may or may not be relevent to others, and its just a sharing of opinions.
In my personal opinion, pentax is a very good system, and only got better with K-3 (and i have been using pentax as my main system for almost the last 10 years), but still, i would love to have a lens like canon's 17-55 or 24-70 in the pentax lineup (in terms of AF speed), and I would have loved (and probably would have decided to upgrade) if K-3 had the same degree of pre-focused shutter lag as the upper canon/nikon bodies (shutter lag of 50-60 ms vs 100 ms for the K-3)
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Forum: Troubleshooting and Beginner Help
04-03-2014, 04:41 PM
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Yes, on bodies that can do proper focus tracking, it will not be a matter of AF speed, but AF tacking precision/granularity (and K-5 has none). However, the photo was more to illustrate that during daylight moderately fast objects moving towards you at moderate apertures will stay in focus even with a K-5 + 18-135 (at least that was my experience). It will be a different story if it is more at the tele part of the reach, or lowlight condition..
Sorry for saying the same thing again, but if i had one wish, it would be pentax to start to develop fast standard zoom AF. It would be a logical choice, afterall in K-3 they invested in the AF system. Until then, on my side i decided to try and re-purchase canon bodies for situation that is more demanding on the shot timing (the other drawback of Pentax is that pre-focus lag is about twice as long as canon or nikon mid-level bodies... 100 ms vs 50 ms, for me this is the most annoying part as kids change their expression or turnaround very quickly...)
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Forum: Troubleshooting and Beginner Help
04-03-2014, 04:26 PM
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what about battery ? i sometimes experienced this when using third party battery or old battery
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Forum: Troubleshooting and Beginner Help
04-03-2014, 07:34 AM
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From what i gathered (i did not use it directly), it is not as fast as 17-50 F2.8, I did hear good comments about its IQ, and has also the benefit of smaller size. With pentax, if speed matters even a little bit, you need to use the fastest possible AF lens, and even then you are basically at the level of a mediocre zoom in canon in terms of single shot AF.
However i would also say that canon is exemplary in terms of AF speed, try a entry level nikon (D5xxx, D3xxx) with its kit lens, it is NOT faster than a pentax and is quite a bit slower than canon... Nowadays fast mirrorless cameras and premium compacts are actually sometimes even better than mediocre DSLR PDAF systems (i have a EM5 and, RX100 and they aren't slower than my K-5...)
I attach a couple of photos i took with 18-135 and K-5 where my kid was running towards me at full speed (he was trying to throw the snowball at K-5, and succeeded..), in broad daylight and at not too demanding situation like this (18-135 doesn't have fast aperture, so there is more tolerence to missed focus), its still OKish...
All in all, I think there is some sort of satisfaction in the color rendering, the overall functionality (small but well built, well customizable), the small sized lens (where else can you get a 18-135 whose size is only 7cm in length), the slient shutter sound ... which makes it hard to decide whether we should go for other systems that are much better on some areas (such as AF speed, lens lineup), but does not have those goodies.... On my side, I plan to repurchase a canon body (such as 50D) for the part that demands AF speed
CJ
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Forum: Troubleshooting and Beginner Help
04-02-2014, 08:21 PM
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Hi Chris
Pentax SDM are slow (not faster than pentax screw drive lens), so they are slow to make the micro adjustment, and it will not improve the situation compared to 18-135 (in fact worse)....
Most of the canon USM lenses are very very fast (try using a 24-70L or 17-55) and the micro adjsutment is done extremely quickly. Recent sigma lenses are still better than Pentax, which is why i suggested you try Sigma's 17-50 F2.8 which is one of the best standard zoom lens for Pentax systems (both in terms of IQ and AF speed)
Pentax AF system was lousy in the past, it has improved recently (since K-5), but it will never improve enough unless the lens is upgraded. What i am trying to say is that the bottleneck is more the lens than the body (it used to be both before K-5), the body AF responsiveness of K-3 (or even K-5) is not worse than a rebel (about the same which is not good btw as rebel is an entry), and as lens lineup do not change in a matter of months, the problem is here to stay unless pentax invest the next few years introducing very fast AF lenses (or sigma improves further their AF speed)
The only quick solution is to try to borrow a sigma 17-50 to see if it improves the situation. Otherwise a modern canon model like 70D combined with any decent canon lens will simply blow away if the critical criteria is stopping the action at the moment you see it in the view finder....(to do that you need a lag of around 100 ms)
And yes you are absolutely right, the reviews never focus enough on the auto focus aspect. They are usually very brief, and in my opinion very carelessly analyzed, and as of today there is not a lot of thorough review avaliable on websites regarding AF speed. For example, very few people will know that the lag between Canon and Nikon mid-range system can be quite significant (due to mid-tier lenses on nikon being quite a bitslower than canon in terms of AF speed + AF confirmation speed of the body also being worse in Nikon)
Then there is also the aspect of tracking (AF-C), which is a whole new story which i dont' think is your focus so I won't go there... With a pentax system you have to do a bit of anticipating shooting to get the right moment (e.g. shoot 0.1-0.2 s before your anticipated moment)... sad isn't it ??
Rgds
CJ
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Forum: Troubleshooting and Beginner Help
03-31-2014, 05:37 PM
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hi
its a little sad to hear that my reply is not helpful, i did read all your previous posts, and i actually created my forum membership because i wanted to reply to this thread - as i have been struggling with the same question for the last few years !
i will re-clarify : an old rebel body does not perform closed loop focus so it is normal there is no hesitation. I am sure K-3 does a closed loop algorithm. Recent canon entry models perform closed loop algorithm
But again, it is the lens which is the real culprit, because makng micro adjustment 2-3 times before settling in will be very noticeable with screw lenses, while with a fast USM (eg canon), you wont hear a thing or feel any vibration
i have shot tamron 17-50 with both my pentax k-5 and canon bodies, the focus speed is basically the same.
same on the canon side, if u use lens like 50mm f1.4 or old 35mm f2 (which is not super quiet) you will notice its very obviously doing some last second back/forth before settling down the AF (you dont feel this with lens like 24-70, 17-55, 17-85, 15-85)
so again, what i am trying to tell you is that
1. it is normal that an autofocus algorithm does not finish with a single calculation/move (open loop), and does a few more moves. this additional move is more visible on camera that does closed loop AF, and has screw drive lens which is unable to make quick and undiscernable micro movements, though on some cases its actually quite fast (35mm f2.4), but just noisy
2. The problem of speed of single shot AF responsiveness of Pentax is not in the body (it peforma on par with canon if using the same third party lens), so future model is unlikely to address this issue, but introducing a new lens lineup whose focusing motor is comparable with canon will address this issue (unlikely to happen). As of today, the fastest focus on pentax is sigma 17-50 / 70-200 lineup where the speed is slightly slower than most canon USM zoom, but faster than pentax zoom
3. Pentax is not the right system to shoot where the limiting factor for getting the shot is AF speed. it is adequate for normal day to day situation, but is very difficult to use on situation where things are moving, there is a reason why action shooters mostly use higherend canon/nikon.
I personally think the best would be to try another lens (sigma 17-50) and if thats also a problem, to switch to canon
CJ
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Forum: Troubleshooting and Beginner Help
03-24-2014, 10:28 PM
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Hi again,
The AF slowness of current lineup of Pentax DSLR is not linked to the body, but linked to the lens. You can experiment by focusing on one point, and trying to focus again on exactly that point. It will be less than 0.2 sec. Now focus the lens at infinity and then focus at something close.... Depending on the lens thats going to be from 0.2 S (fastest canon lenses) to over 1S (slower pentax lens like 55-300), for 18-135 it should be quite fast at the wide end (0.2-0.3 s) and at tele end it should be quite a bit slower than canon lenses (close to 1S)
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Forum: Troubleshooting and Beginner Help
02-28-2014, 05:05 PM
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and to add one more comment, within a zoom lens the AF performance variance is worse in pentax between wide / tele end (though 18-135 is not super serious on this regards). make the test on the wider angle end or middle part of the zoom of 18-135 and the gap should be smaller. Though it doesn't solve the fact that focusing on tele end of zoom is a struggle for pentax systems.....
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Forum: Troubleshooting and Beginner Help
02-28-2014, 04:57 PM
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Hi Chris
I've been reading this thread with interest, as one day I may change my body (K-5) to a K-3 or an equivalent canon body... While I have not shot every single DSLR in the world, I have experienced both pentax and canon DSLR to a fair extent since 2006, and AF was something that i have been thinking a lot during the last few years. I will try to focus my comments purely on the aspect of AF speed on single shot mode without flash.
I think part of your frustration might be solved by starting to gather data from test sites that have been done in a controlled way (not all test site results are "useful"). I think imaging-resources, will give you valuable information on A) the speed of the camera algortihm to determine focus, and B) the pre-focus shutter-lag .... it exists in its "performance" tab. Then if you go to a website called lenstip.com, it gives you some useful information on the C) speed of the lens itself.
After going through those test data (+ reflecting with my actual experience with various pentax/canon cameras), I have made some reflections to my understanding of the two systems in terms of AF performance
(A) AF module performance : First of all, within CANON cameras, somewhere in 2009 the AF algorithm seems to have changed (and this is also seen in a few articles in the web), so that canon is performing what we call "closed loop" AF check in newer camera. I also suspect that this is only applied on the single shot AF of CANON and not on AI servo. This means that on single shot mode, the older CANON cameras may actually be faster than the newer models (though likely less accurate). On pentax side, i noticed a subtle change happening between K-5 model and models after K-30 (where it actually became a little slower since K-30), i don't know if it is linked to applying a stronger closed loop process, but K-5 had a lot of complaints on AF accuracy which was solved from K-30 and i think they are linked. Let me give you some figures....
Pentax models before K-5 : around 0.1 s (only AF module lag)
Pentax models after K-5 : around 0.1 - 0.2 s (K-3 should be around 0.15 s)
Canon earlier entry models : 0.1-0.2s
Canon recent entry models : 0.2-0.3s
Canon performance models : 0.1s (eg. 7D, 50D, 70D)
(B) Pre focus lag : This obviously applies only on situation where you have already aquired focus, but i wanted to hilight there are some meaningful performance difference on prefocus lag between pentax and canon/nikon. Pentax model are more like 0.1s, canon/nikon entry is 0.1s, but the higherend models (d7000, 70d) are more like 0.05s, this difference for me was subtly annoying on some subjects (such as kids facial expression changing quickly)
(C) Lens speed : 18-135 is one of the faster lens Pentax has, it should rack from close to infinity in around 0.7 sec (some pentax and nikon lens can take 1s). What we call relatively fast AF lens (e.g. sigma 17-50, or canon 24-105) should be able to do this in 0.5 sec. Super fast lens (e.g. canon 15-85, 85.8, 17-55, 24-70, 70-200) can do this in 0.2-0.3 sec. All in all, most of the lens that are mountable in Pentax are on average quite a bit slower than Canon lens, including not so advanced lens like 17-85, 28-135
So between K-3 + 18-135 and 300D + 28-80 (i don't know this lens), the AF performance should be faster in 300D (not by a margin of 1 sec, but maybe 0.5 sec if we are moving the whole length of the focus range). This gap will be much smaller if you have already prefocused on a similar distance (which i do all the time for pentax), and K-3 should theoreticlally be much more accurate if you have calibrated your AF microadjust.
I personally used mostly a 450D a lot during 2008-2010 with various lenses and I know it is quite a bit faster (a little with kit lens, and significantly with good lens) than K-5 for example (which i also used extensively during the last few years). The gap widens slightly further with more advanced canon models.
I think though in real-life your problem experienced might be more linked to the flash performance of Pentax system. And on daylight conditions with 18-135, i have had no problems to nail focus on fast moving kids (but i couldn't do this with slower pentax lens like 43.9 or 55-300).
My conclusion is the AF wise, canon is just quite a bit ahead of pentax. Pentax is usable but you have to adapt (e.g. prefocus frequently to nearby distance) and make sure you use above average performing lenses (not in terms of optics but in terms of AF speed). On the otherhand nothing to do with AF, but while the keeper rate is lower in pentax on the AF part, i throw away more images from canon (even 5d mk ii) on lowlight than K-5 because K-5 has a very good shadow recovery on post process (and i don't like dark pictures and i tend to lift the shadows in my PP), so the overall keeper for me is complex to determine =)
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