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02-20-2020, 08:31 PM   #1
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AF on K-1 and K-3?

I just got a K-1 and K-3 and love most everything about them except, the AF. I'm using the 55mm 1.4, and older Tamron 90mm 2.8 macro the 70mm 2.4 and an 18-50 Sigma 2.8 for now. I seem to be missing focus on some pics and not really sharp and they are pretty slow to focus. Is it the lenses or is Pentax AF really this bad? Do I need the new Pentax lenses for decent, accurate AF? I dumped most of my Sony E gear because I hate everything about Sony BUT the AF. Any insight would be greatly appreciated, I'm not a newbie photog so it's not technique, meaning I had a focus point right on a persons eye. I'm really surprised at how slow focus is in good light

02-20-2020, 08:41 PM   #2
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may be you need to make focus fine adjustments for the specific lens
02-20-2020, 09:26 PM - 1 Like   #3
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QuoteOriginally posted by ddinmpls Quote
I'm using the 55mm 1.4, and older Tamron 90mm 2.8 macro the 70mm 2.4 and an 18-50 Sigma 2.8 for now....
I dumped most of my Sony E gear because I hate everything about Sony BUT the AF. ...
I think we have users shoot both Pentax and Sony mirrorless here. You should get more satisfy answer (than my answer) soon.

I am using a K3 and I have the 55 1.4 (if you mean DA*55). It is one of the best auto-focus lens on my K3 (in term of accuracy not the speed) when shoot at night. Its f1.4 helps on accuracy but the lens slow auto focus is a well know issue.
I have shot with many Sony shooters, mostly a7 II and III at night. Their Auto focus leave me (K3 + DA*55) in the dust. I hope you don’t expect K3+55* to be anywhere close to what you used to have with Sony. When I want to use auto focus at night, using face detection or tracking in combination with Live view can help a lot.
02-20-2020, 09:29 PM   #4
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I my experience accurate and/or fast focus with the K-3 and K-1 is probably more to do with the lenses than the cameras.
I use a K-1 and K-3 II with a DFA 150-450 and focus is fast and accurate.
I also use a Sigma 24-70 and a Sigma 85 with these bodies, and whilst the focus is very fast with both bodies, they can sometimes lock onto a point where I didn't want it to. This behaviour seems to be a bit of Sigma trait.
I use single point focus, usually AF-C, and back button focussing.
Technique can make a big difference, but lenses can be quite variable.
I should add that AF camera settings can have quite an effect. Check your operator manual and maybe experiment with AF settings.
Cheers,
Terry


Last edited by tduell; 02-20-2020 at 09:58 PM. Reason: Additional info
02-20-2020, 09:47 PM   #5
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QuoteOriginally posted by tokyoscape Quote
I think we have users shoot both Pentax and Sony mirrorless here. You should get more satisfy answer (than my answer) soon.

I am using a K3 and I have the 55 1.4 (if you mean DA*55). It is one of the best auto-focus lens on my K3 (in term of accuracy not the speed) when shoot at night. Its f1.4 helps on accuracy but the lens slow auto focus is a well know issue.
I have shot with many Sony shooters, mostly a7 II and III at night. Their Auto focus leave me (K3 + DA*55) in the dust. I hope you don’t expect K3+55* to be anywhere close to what you used to have with Sony. When I want to use auto focus at night, using face detection or tracking in combination with Live view can help a lot.
Thanks for the insight

---------- Post added 02-20-20 at 10:49 PM ----------

QuoteOriginally posted by tduell Quote
I my experience accurate and/or fast focus with the K-3 and K-1 is probably more to do with the lenses than the cameras.
I use a K-1 and K-3 II with a DFA 150-450 and focus is fast and accurate.
I also use a Sigma 24-70 and a Sigma 85 with these bodies, and whilst the focus is very fast with both bodies, they can sometimes lock onto a point where I didn't want it to. This behaviour seems to be a bit of Sigma trait.
I use single point focus, usually AF-C, and back button focussing.
Technique can make a big difference, but lenses can be quite variable.

Cheers,
Terry
Thanks,Terry. I may rent a couple of the new DFA's and see
02-21-2020, 12:11 AM   #6
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Evening, Just in case, let me go back to the beginning on focusing. DSLRs have two separate focusing systems - one through the viewfinder and one with liveview (which is essentially the same approach as mirrorless cameras utilize). I'm going to assume that you are finding that the bulk of the problems is using the viewfinder.
  • Viewfinder - The light comes in through the lens, bounces off the mirror and up through the prism viewfinder to your eye. When you autofocus, there is a hole in the mirror, that takes part of the light and ricochets it down to the bottom of the camera where there is some AF circuits that figures out if the image is in focus, and if not, commands the lens to adjust the focus (out or in) to bring it into what it thinks as "in focus", then it takes the picture.
  • LiveView - Again the light comes into through the lens, and since the mirror is up (preventing the use of the optical viewfinder), the light goes directly to the sensor, where the sensor detects focus, commands the lens to adjust focus, then captures the image.
The difference between the two is that liveview is right off the sensor, so the image is AF on to the sensor, and the focus should be perfect. With the optical viewfinder, the AF circuits residing on the bottom of the camera need to be aligned / calibrated so that when the AF circuits believes the image is in focus, it will really be in focus on the sensor. If not, the camera (K1, K3, etc.) has a fine tuning calibration process that you can do for each lens. The camera body has the ability to store these calibration data for 20 individual lenses.

A simple test would be to put the camera on a tripod or flat surface, AF with the viewfinder, take the picture. Then with out touching a thing, put the camera into LiveView, AF and take the picture. Then on your PC view each image - where the liveview image should be in perfect focus, and the viewfinder focused image may be a tad off. This is refereed to as either front focusing or back focusing. With front focusing, the area in front of where you actually focused is in sharp focus and the rest of the image is off. With back focusing, some of the area behind where you actually focused is in sharp focus, while where you actually focused is off.Third party lenses can have AF problems. The Sigma 18-3/f1.8 lens optically is a great lens, but individual copies are notorious for having AF problems (across Canon, Nikon and Pentax). The third parties have to reverse engineer each AF lens system for each camera brand. This usually works well, but sometimes - it doesn't work as well as intended.


Last edited by interested_observer; 02-21-2020 at 12:18 AM.
02-21-2020, 12:22 AM   #7
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QuoteOriginally posted by ddinmpls Quote
I just got a K-1 and K-3 and love most everything about them except, the AF. I'm using the 55mm 1.4, and older Tamron 90mm 2.8 macro the 70mm 2.4 and an 18-50 Sigma 2.8 for now. I seem to be missing focus on some pics and not really sharp and they are pretty slow to focus. Is it the lenses or is Pentax AF really this bad? Do I need the new Pentax lenses for decent, accurate AF? I dumped most of my Sony E gear because I hate everything about Sony BUT the AF. Any insight would be greatly appreciated, I'm not a newbie photog so it's not technique, meaning I had a focus point right on a persons eye. I'm really surprised at how slow focus is in good light
Some of both I guess. The Sony AF is better. Looking at your lenses, the 55mm and 90mm are both rather slow in focusing. You should still get good results on non moving objects (people are not) with both of the lenses. The 70mm is relativly fast for a screewdrive lens. I do not know about the Sigma 18-50, never used it.

You will get a higher keeper rate after getting used to it. In the end, you need to compensate some af issues with your technique. Your af keeper rate propably wont hit the rate you can produce with the Sonys, but maybe in other terms like composition it is the opposite.

You should however look for systematical errors, in other words, if the lenses need calibration.


Last edited by WorksAsIntended; 02-21-2020 at 12:29 AM.
02-21-2020, 04:08 AM   #8
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A couple considerations, speaking for the K-1:
•As some members have said, perform AF fine adjustment; it should help a lot.
•What AF mode are you using? Spot AF (center point only) works best* - Auto-33 is as good as useless in many cases unfortunately.
•All of the lenses you mention are either screwdrive or older SDM in-lens motor. Their performance will not be exactly as good as a modern lens with a high-end motor, but they should do the trick. Expect some inaccuracies if you go for shallow DOF near infinity (say, trying to use your 90mm at f/2.8 to focus on a person 17 meters away but grabbing the person immediately behind them), but adjustment and proper technique will make up for most of the AF woes.
02-21-2020, 04:28 AM   #9
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I guess my comment would be that at least a couple of your lenses are pretty slow to focus. Macro lenses have a really long focus throw and often can take awhile to "get there" and the DA *55 has a super slow SDM that means that you have time to make yourself a cup of coffee and drink it before it actually locks focus.

That said, if you are taking photos of something that holds still, you should be able to get decent focus with any of your lenses. I would definitely do some focus calibration. I tend to use live view to calibrate things and it seems to work pretty well...

Camera AF Microadjustment - for free Canon, Nikon, Sony - any camera with adjustment
02-21-2020, 04:33 AM - 1 Like   #10
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Calibration should not be done in livefiew, as it does not consider a pretty much always present slight decalibration of the af module.
It is not the same focus system and therefore you cannot calibrate it this way.
Edit: of course this is only true if not mainly using livefiew for shooting.
02-21-2020, 04:55 AM   #11
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I wonder if this also could be having an effect on " accurate focus "

I was researching IBIS to answer another thread and found this video - it indicates that it may take time to have the IBIS take effect and failure to allow that time could cause problems
QuoteQuote:
Pentax Shake Reduction Tutorial
A guide on how to get the most out of in-camera stabilization
By PF Staff in Tutorial Videos on May 12, 2013
Pentax Shake Reduction Tutorial
All modern Pentax DSLRs include Shake Reduction, a mechanism which stabilizes the sensor to reduce camera shake regardless of the lens being used. This means that no matter what lens you put on your Pentax, you'll enjoy image stabilization. The SR system's compensation thus enables you to capture sharp hand-held shots at 2-5 stops slower than normal. For example, a photo shot at 1/15s with SR enabled will likely be just as sharp as one shot at 1/60s or 1/120s with SR off. The latest Pentax bodies even include 5-axis stabilization!

However, in order to get the most out of the SR mechanism, there are a few things you should note. For instance, you cannot assume that SR is always on; you have to arm it by half-pressing the shutter button before actually taking the photo. We talk about this and much more in our latest video tutorial.
Enjoy!
Read more at: Pentax Shake Reduction Tutorial - Tutorial Videos | PentaxForums.com

now the article is from 2013 and perhaps Pentax IBIS has been improved ??
02-21-2020, 04:59 AM   #12
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QuoteOriginally posted by aslyfox Quote
I wonder if this also could be having an effect on " accurate focus "

I was researching IBIS to answer another thread and found this video - it indicates that it may take time to have the IBIS take effect and failure to allow that time could cause problems


Read more at: Pentax Shake Reduction Tutorial - Tutorial Videos | PentaxForums.com

now the article is from 2013 and perhaps Pentax IBIS has been improved ??
Interesting point. As I never shoot any pictures without half pressing first I never encountered this.
02-21-2020, 05:07 AM   #13
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QuoteOriginally posted by WorksAsIntended Quote
Interesting point. As I never shoot any pictures without half pressing first I never encountered this.
I use " back button " AF and am not sure if I press the shutter smoothly or pause at half shutter

I will now be pausing unless I learn that the SR system has been improved

I started a new thread to try to find out from our knowledgeable members

Question about properly using Pentax IBIS - has it improved ? - PentaxForums.com
02-21-2020, 05:39 AM   #14
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QuoteOriginally posted by ddinmpls Quote
I just got a K-1 and K-3 and love most everything about them except, the AF. I'm using the 55mm 1.4, and older Tamron 90mm 2.8 macro the 70mm 2.4 and an 18-50 Sigma 2.8 for now. I seem to be missing focus on some pics and not really sharp and they are pretty slow to focus. Is it the lenses or is Pentax AF really this bad? Do I need the new Pentax lenses for decent, accurate AF? I dumped most of my Sony E gear because I hate everything about Sony BUT the AF. Any insight would be greatly appreciated, I'm not a newbie photog so it's not technique, meaning I had a focus point right on a persons eye. I'm really surprised at how slow focus is in good light
For me as a Pentaxian it is a bit of a wild goose chase if you do not specify with which lens you miss the focus. Perhaps you bought both second hand and the last owner changed the settings for AF. The settings might then apply to the lenses he of she used and not yours. Slow focusing is something I do not recognize with Pentax. So there are a number of reasons for missing focus. I do know that some third party lenses, especially Sigma, make it a bit harder for a Pentax camera to focus. So miss focusing is either the camera's fault or the lenses. But as the DA* 55mm is also at fault I guess that someone has fiddled with the settings for AF.
02-21-2020, 05:44 AM   #15
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even with SR, how you use the camera can make a difference

I try to follow the techniques describe in this article any time I use large lenses:
QuoteQuote:
Introduction
Recently, a member over in the DPReview Pentax SLR Forum was expressing his frustration with vibration control. That's when it occurred to me: there are no tutorials out there that really give an in-depth explanation as to how to improve your photography technique for those inevitably blurry long-exposures. I'm not saying said member has terrible technique, but there really isn't anything out there to address it, especially for us newbies that are just starting.

Granted, he was referring to 1/8s shutter speeds on a medium telephoto (70-200 in 35mm format), however I have had success at 1/4s with my 55-300 (80-450 in 35mm format) at the long end (yes, with Shake Reduction enabled). Does it make for a Nat Geo worthy photo? No, of course not, let's not be ridiculous. However when you magically find yourself in the Vatican with no tripod during Christmas Mass and you are only allowed to creep up to the Pulpit so much before you are removed by the Swiss Guard after being told to stay back for the third time (true story), you have to be prepared to use the equipment you have despite its limitations. I was able to obtain some keepers of the Pope that I would never have otherwise, had I not followed the steps I am about to talk about. Allow me to offer a military approach to camera shooting that I can attribute only to extensive marksmanship training.

I am by no measures a "pro," but I understand my fundamentals very well, and this specific set has been drilled into my head so many times that it is now second-nature. I am going to teach you how to "shoot" your camera like a high end rifle because at the end of the day, the fundamentals stay the same in every aspect. If you are an avid shooter (of the projectile type), then you do all of this probably without even thinking about it, especially if you are like some of my friends that exited the womb wielding a 30 Aught Six (7.62mm for those of you unfamiliar with American calibers).

Or, if you are like me and never touched a weapon until your adult life by way of raising your right hand, your Drill Sergeants provided that intimate, patient instruction and guidance that makes you think of warm country evenings at home with grandma: Steady Position, Breathing Control, Aiming and Sight Picture, and Trigger (Shutter) Squeeze.


Now let's break it down...


Read more at: Making the Most of Long Exposure Handhelds - Introduction - In-Depth Articles
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