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07-02-2012, 10:22 AM   #1
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I'm getting sick and tired of unreliable AF (rant)

Bought K-5 about 2 months ago. It suffered from front focus issue in low light. Got it repaired and while the low light issue was solved, it now back focused under normal light - to a degree that too many pics were unusable.

(2012.06.12 - Zafar Iqbal's Photos | SmugMug - primarily pics taken by my K-5 after I got it back from repairs)

Tried a demo model at the shop. Same issue. They opened a brand new K-5 box. Same issue. They were willing to make a swap if had been satisfactory, but it wasn't, so my cam went back in for repairs. The shop was kind enough to find a K-r I could use. AF issues again. Huge misses in overcast type lighting. It seems to miss the focus in both normal and low light.

Can't find much about normal/bright light focusing issues. So it's either something new, or I'm expecting too much? If I'm expecting too much then the (Pentax) Phase Detection AF is utter crap.

Been a very happy owner of the K-x. Sure, it misses focus now and then but mostly in extreme cases - super brights or very dark subjects/light - or stuff that confuses the AF such as tons of branches in front of a face or whatever - it's also clear the CDAF gives up quicker than PDAF - but it's way more reliable! I don't expect any cam to work perfectly under those circumstances, but the K-5 and K-r are a complete joke. The K-r is much better, but random. When I think it should nail the focus it doesn't. When I don't think it will focus properly, it does.. it's very. Can't compensate enough with with Micro Adjustment.

Tried with 3 lenses:
Pentax 70mm Limited
Tamron 90mm Macro
Sigma 70-200mm APO

All at widest aperture.

Hate to say this, but when I get my K-5 back and it shows still has unacceptable issues, I'll ask for my money back and look for some other brand :/


Last edited by Zafar Iqbal; 10-29-2013 at 02:02 PM.
07-02-2012, 10:30 AM   #2
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There are more then enough threads about this here, good luck searching.
07-02-2012, 10:46 AM   #3
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QuoteOriginally posted by Zafar Iqbal Quote
Hate to say this, but when I get my K-5 back and it shows still has unacceptable issues, I'll ask for my money back and look for some other brand :/

Good luck with that, I'm sure you'll find something that suits you eventually.
My K-x experience is similar to yours, but personally I mostly preffer MF.
07-02-2012, 10:55 AM   #4
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From the photos I looked at in that gallery you posted, it doesn't appear to be that the camera is back/front focusing at all. It is selecting what is dead-center in the frame as the focus point.


This is not back focus, it just picked up the building behind the light as the focal point and this would have been evident in the viewfinder. Back/front focus is typically a matter of inches off, not hundreds of feet.
Try setting the camera to use multi-point AF for a while and see what results you get.

And stop down; f/2.4 @ 1/1600s is a lot less forgiving than f/9 @ 1/200s. There's no need to shoot wide open all the time.

07-02-2012, 10:56 AM   #5
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QuoteOriginally posted by Anvh Quote
There are more then enough threads about this here, good luck searching.

And there needs to be many more IMO.

I say keep the issue of crappy AF at the forefront until pentax turns out a camera that actually benefits from the use of autofocus.
07-02-2012, 11:18 AM   #6
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Did you use the in-camera AF adjust to set up your camera/lenses?
07-02-2012, 11:18 AM   #7
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There was a thread recently about the actual AF sensors being a lot bigger than most people expect, and therefore less precise. I wonder if that is the true issue here, not FF/BF.
07-02-2012, 12:03 PM   #8
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QuoteOriginally posted by Venturi Quote
This is not back focus, it just picked up the building behind the light as the focal point and this would have been evident in the viewfinder. Back/front focus is typically a matter of inches off, not hundreds of feet.
Try setting the camera to use multi-point AF for a while and see what results you get.
I aimed for the green light 3 times - missed every time. A larger focus point may or may not make focusing with the K-5 more tricky, but I have other examples with street signs covering a much larger area, yet the focus is way off.

Besides, my 70mm Limited isn't *that* soft even if it did focus on whatever is right in the middle - which it didn't. I recomposed as mentioned in the description of the photos.

QuoteOriginally posted by Venturi Quote
And stop down; f/2.4 @ 1/1600s is a lot less forgiving than f/9 @ 1/200s. There's no need to shoot wide open all the time.
I didn't purchase fast lenses to stop them down. All shots are wide open in that particular album because I noticed this problem. It's easier to see vs. f9.

QuoteOriginally posted by JohnX Quote
Did you use the in-camera AF adjust to set up your camera/lenses?
Yes, I had it maxed out but it still wasn't sufficient. I think I used values at 0, -10 and +10 in photo 6, 7 and 8. None of the values got me spot on or even lead to front focusing, which would be an indication ofgoing too far with the values.

QuoteOriginally posted by ihasa Quote
There was a thread recently about the actual AF sensors being a lot bigger than most people expect, and therefore less precise. I wonder if that is the true issue here, not FF/BF.
I'm aware of focus point having a size big enough to conflict with what I want in focus. I learned this with my K-x - this is why I have 3 photos of the street light. I tried again and again to have the camera lock on to it, but it never could.

I should have mentioned my images scale depending on whatever browser size you have. Bigger/Original sizes can be seen if you hover the mouse over the displayed image, and chose a size from the popup.

07-02-2012, 12:11 PM   #9
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I guess I would send the camera in if you are certain there is no user error. I have no trouble focusing with my K5s, except with wide angle lenses where my subject is positioned pretty close to the back ground. I find the center auto focus point is the one that struggles the most -- it is just bigger and tends to grab onto whatever is closest and most contrasty in the general area. Edge points are smaller and seem not to focus on extraneous stuff as much.
07-02-2012, 12:35 PM   #10
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QuoteOriginally posted by SALUKIS97 Quote
And there needs to be many more IMO.

I say keep the issue of crappy AF at the forefront until pentax turns out a camera that actually benefits from the use of autofocus.
I think we would all get sick of it if some start one weekly instead of monthly.

But seeing the photo this an other issue all together.
It looks like it's focusing on something else then intended to so it's not a front or back focusing issue at all.

So sorry for my mistake.

It's strange the camera didn't get it, did it actual search for the focus point often you need to help it a bit, most likely your focus was closer to the wall then the light so it focused on that.

Last edited by Anvh; 07-02-2012 at 12:43 PM.
07-02-2012, 01:17 PM   #11
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QuoteOriginally posted by Rondec Quote
I guess I would send the camera in if you are certain there is no user error. I have no trouble focusing with my K5s, except with wide angle lenses where my subject is positioned pretty close to the back ground. I find the center auto focus point is the one that struggles the most -- it is just bigger and tends to grab onto whatever is closest and most contrasty in the general area. Edge points are smaller and seem not to focus on extraneous stuff as much.
There is always a chance of user error and I wont deny it - but I will deny the chance of user error in *all* of the photos. I was convinced there was an issue and had therefor the cam sent back to repairs again. One of the shop keepers also had his with different K-5 and turned to the same conclusion as me.

QuoteOriginally posted by Anvh Quote
But seeing the photo this an other issue all together.
It looks like it's focusing on something else then intended to so it's not a front or back focusing issue at all.

So sorry for my mistake.

It's strange the camera didn't get it, did it actual search for the focus point often you need to help it a bit, most likely your focus was closer to the wall then the light so it focused on that.
the focus must be some where and since it consistantly back focused, it's easier to think the camera may have been confused and focused on a wrong area. I had a 1 long work from pre-under and post sunset and noticed how the focus got closer and closer to where it needed to be as the light level went lower and lower. This adds to the indication that something is off.

Re the streetlight: Perhaps, but it is still just a single scenario out of many.

I just uploaded pics taken by the K-r - front focus this time:
2012.07.02 - Zafar Iqbal's Photos | SmugMug

All of the pics may not be valid issue examples. I'm no AF testing expert. All I know, is that my K-x is far more reliable. With the K-r I had many more (vs. K-5) properly focused photos, but as mentioned originally, the K-r seems to be unreliable and random to a higher degree wheres the K-5 was just off most of the time - the K-r mostly front focuses yet there are few shots with back focus going on (like the window frame shots).

Photo# 12 was shot @ f9.5 and the off focus is still very clear.

Ps. if you cant see the new pics then its because they are still being processed by the server.

Last edited by Zafar Iqbal; 10-29-2013 at 02:02 PM.
07-02-2012, 01:26 PM   #12
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QuoteOriginally posted by Anvh Quote
It's strange the camera didn't get it, did it actual search for the focus point often you need to help it a bit, most likely your focus was closer to the wall then the light so it focused on that.
I get more focus hunting on my K-x than K-5 or K-r. With those focus just snaps. Just not necessarily the right place.

I remember thinking its as if multi point AF was enabled even though it wasn't.
07-02-2012, 02:04 PM   #13
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What AF mode are you using (AF-S, AF-C)? Are you using Auto, Center, Single point (might be more on K-5)?
07-02-2012, 02:19 PM   #14
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I don't know if you can retry the shot?
I suggest you first focus close manual, just give it a quick turn so that the focus is roughly there and then enable the autofucos see if that helps.

Also which mode is the camera on just make sure it isnt on the green mode, it might put that AF on multi-select by default.


Anyway it's strange it front and back focus all over the place, it's known that the K5 backfocus under tungsten light but never heard of problems during daylight thats why i doubt the problems are related to that.

Last edited by Anvh; 07-02-2012 at 02:25 PM.
07-02-2012, 02:28 PM   #15
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AF-S and Single (center) Point for the majority of the shots, although I suspect *all* uploaded photos were shot like that.

Just been shooting in a small shop. The K-r is much more reliable and accurate now (midnight in 30 mins). I didn't change any setting on the cam since the last shots.

There were few flukes here and there, but nothing that would get me too worried. Odd thing was though, that sometimes it locks "in the air" seemingly no matter what I did. LED lights also through the focus way off. Can't remember how my K-x is on that area. But overall: 95% (or more) successfully focused pics. Theres tons of small stuff here. Things/areas I can look though etc. AF had little problem (had to guide it, but I'm used to that from my K-x as well) with stuff much much smaller that the type of things I've been aiming in the daylight photos.

It never refused to lock focus. Only when I thought of it and then aimed the camera at a black shirt, hanging in a shadow

So, during the day: A wild beast that refuses to be tamed.
night time: A sweet teddybear.

My K-5 was pretty much like that as well. First during low light. Then, after the first round of repairs, during normal light
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