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12-23-2011, 06:37 PM   #1
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Pentax K-5 AF accuracy

Is there any way of improving the AF accuracy or consistency?

Because I am bored on Christmas Eve and it's raining outside, I have been cleaning my cameras and playing around.

Ever since I bought a Sony NEX-5N, I have been impressed by how much more accurate it's AF is compared to Pentax - I seem to nail in focus photos much more often than on the K-5.

So I played around with K-5 and the FA43 Limited (okay it's low light, given off by a single energy saver bulb) and I noticed the AF is just not very consistent. Sometimes it will get the focus right, but more often than not it's slightly front focusing.

In comparison, focusing using Live View nails the focus each and every time.

I have a Katz eye focusing screen, and I noticed that whenever using AF, often the resultant focus lock is slightly "off". If I manually correct it, I get better results.

I tried to correct the front focus using the AF fine adjustment, but the problem is because the AF focus is inconsistent, there is no single adjustment setting that will improve focusing.

Should I send the K-5 for repair? Will that improve AF consistency?

By the way, out of curiosity, I repeated the test on my K10D. And it has exactly the same problem - AF is just not very consistent, and often the focus is slightly "off." Based on this I am wondering whether this is a common characteristic for Pentax bodies.

12-23-2011, 07:23 PM   #2
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hahah...

One day near the future I will buy a canon or a nikon - and I bet you I will be an expert photographer immediately.

2 days ago i went to a family shoot with my K5 and Metz 58. Set the metz to slave, set it off camera, set it to EV -3, and took several test shots. Everything on manual. Great exposure. Decided to put my AF58 on the camera as a master. WHAM. Everything went overexposed, the Metz 58 fired full power..or the AF58 fired too (which shouldnt have happened, because it was set only to control).
Took the AF58 out - and used the onboard flash again to control the Metz. Something must have broke, because now the Metz fires full power all the time. For no reason.
Finally had to do the shot without flash, because I couldnt get the Metz to fire lower anymore.

Then yesterday, did live view for focus on a different shooting, this time model shoot. It was on focus selection. Held the button, select where i want to focus....live view...good. Take a shot. Then another. Then another. Reposition model. Another shot. then...suddenly the manual focusing went awry. No matter what I did, it was autofocusing. Turned it back off. Then back on. Switch the selector to 3 different focus mode, then back to focus selection mode. Nothing. Took another shot. But i fumbled for a bit, then started taking shots manually without live view. Took it off the tripod and hand held the camera. Whatever, then suddenly it worked again.

I dont know. Maybe i will read the manual again. I used to think I just dont know how to use this. Now i am thinking the software is buggy. Sometimes it breaks..can't duplicate it to complain, but it will happen when i need it. I have never complained about front focus, back focus, etc...i just pick up the camera, and adjust focus. I am comfy shooting manual, setting manual. I love my camera. I do not like it when it does funny things on me when I am doing a shoot though - i want it to reliably do something it was doing minutes ago, continuously. Still looking for a Pentax FF.

I am not sending my camera in for repair unless it dies on me. As far as I can tell things just kind of go awry when I start getting fancy. Today shoot wedding ..one setting. Tomorrow shoot indoor small room - bring 3 different flash brands - and try and fire them off each other...things gets hairy. I should have brought radio trigger so I can set the power manually. Then the next day do studio shooting with yet different lights and different focusing and metering. Things gets funny.
Hijacking your thread, apparently . But i dont think you'd get much out of sending the camera for repair. If its truly broken, then maybe they can adjust it. As far as i can tell about these problems, every unique camera combination needs a different adjustment with different unique lenses..even if they are all the same model. So you need to send in your body and all your lenses and they will fix ("calibrate") it for you. I would think these kind of personalized fix would then be problematic if you buy another lens. LOL. gotta send it back in.

I dont think yours is truly broken - as you never had problem using it by itself. Its just that now you compare it to a completely different camera, you feel its performance is sub-par.

Hijacked your thread to complain! Now back to working on pictures.
12-23-2011, 07:41 PM   #3
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QuoteOriginally posted by Christine Tham Quote
Based on this I am wondering whether this is a common characteristic for Pentax bodies.
I don't know whether Pentax truly suffers more than other bodies from this (although from reading many threads here and elsewhere I get the feeling that AF accuracy is not counted among the brand's advantages over other brands, to say the least) but it seems to me what you're observing is a common characteristic for phase detection AF in general.

I noticed also that the AF is much more accurate with my LX-5 point and shoot (even allowing for the much greater depth of field) than with my K-7 and K-5 -- however, it's also slower, and hunts more.
Personally I prefer accuracy to speed, and I don't care as much as many do about hunting and noise and so on -- I just don't see the point of fast AF if the camera isn't focusing correctly so much of the time -- it's like me declaring myself to be a fast, smooth hurdle jumper -- by just running parallel to the hurdles and never over them! I simply hate phase detection and wish we could have the more accurate contrast detection that LV uses, in the viewfinder. Maybe there's some other advantage to phase detection that I'm unaware of; perhaps the knowledgeable members of this forum will enlighten us.

I've basically resigned myself to stopping down often more than I want to, and manually focusing as often as is practicable (I'm totally dependent on quick shift.)
I drove myself nuts with focus adjustments for the K-7; with the K-5, I've decided to just assume that AF is not my friend, and work around it; life is too short to be obsessing over focus charts.
12-23-2011, 07:47 PM   #4
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Just a minor unrelated point - it's actually more like a fast smooth hurdle jumper who runs through the hurdles.

Point finished, carry on~

12-23-2011, 08:02 PM   #5
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Christine,
In March 2011, you reported:

QuoteQuote:
Wow! The K-5 has AMAZING focus accuracy in low yellowish light!
Pictures of our possums in our backyard (they keep us as pets).

This is taken after 8pm at night (completely dark except for a single yellowish light bulb illuminating the
courtyard at the back of our house)

It was so dark the K-5 hunted around a fair bit, and occasionally turned on the AF assist light, before locking focus.

But every time it locked focus, it got it right.

Here's a shot showing the K-5 correctly focusing on the possum (rather than the branches or the leaves in
front of it)
So were your right back in March or are you right now?

There was a German study this year that showed the K5 outperformed in static AF over Nikon, Canon and Sony.

So perhaps your question has to do with CDAF vice phaseAF.

Noone is going to be able to definitely answer your question until you send both your lens and camera back to Pentax, IMO.
12-23-2011, 08:25 PM   #6
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QuoteOriginally posted by philbaum Quote
So were your right back in March or are you right now?
Well, I thought the K-5 was amazing compared to the K10D (which couldn't really focus all that well in low light, neither could the Canon 1D Mk III)

But then I discovered my NEX-5N could do this, in virtual darkness (there is so little light, I could not even see properly):


So I guess my real question is, is there any way of getting the K-5 to match the AF accuracy of the NEX-5N in anything other than Live View?

Another possibility is that somehow the AF accuracy of the K-5 has deteriorated with age. Because I do seem to recall I was fairly impressed with K-5 accuracy when I first bought it.
12-23-2011, 08:32 PM   #7
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Okay, the rain has stopped, so I managed to take my K-5 outside to take a few shots.

And the annoying imprecision in the AF is STILL THERE, even in relatively good light.

I definitely don't recall the K-5 being this imprecise a few months ago, so I guess the AF accuracy has deteriorated with age. That's not really a good sign. The K-5 now seems to be not much better at focusing compared to the K10D, and I definitely do recall it being significantly better than the K10D when new.

I guess I could send it in to get it fixed, but I'm kind of disappointed. And the cost of repairing it could probably buy me another NEX-5N body.
12-23-2011, 08:43 PM   #8
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Repeat the test in sunlight...the color of light bulbs can affect focus.

Or just use liveview....uses the same contrast detection technique as the NEX5 and P&S's...

12-23-2011, 08:59 PM   #9
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Looks like 2 tungsten to me, 12 and 2 o'clock
12-24-2011, 01:23 AM - 1 Like   #10
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QuoteOriginally posted by Christine Tham Quote
Okay, the rain has stopped, so I managed to take my K-5 outside to take a few shots.

And the annoying imprecision in the AF is STILL THERE, even in relatively good light.

I definitely don't recall the K-5 being this imprecise a few months ago, so I guess the AF accuracy has deteriorated with age. That's not really a good sign. The K-5 now seems to be not much better at focusing compared to the K10D, and I definitely do recall it being significantly better than the K10D when new.

I guess I could send it in to get it fixed, but I'm kind of disappointed. And the cost of repairing it could probably buy me another NEX-5N body.
I don't think there is a problem with AF accuracy deteriorating with age. I've had my K5 since Feb 2011, use it every coupla days, and i'm not seeing any deterioration of the AF accuracy. I also have not noticed AF deterioration with my K10 or K20.

Try this, disable SR and put your K5 on a tripod using a 2 second timer. Put it on an f8 and see if it can take a sharp picture given all these advantages. I define sharpness to be sharp looking edges at 8x enlargement on the lcd screen. If you can't get there, then there is something wrong with the camera. If you can get a sharp edge at f8 but not at f2.8 then you may have front or back focusing.

Call up and tell Pentax servicing what you're seeing and get an estimate. I don't think you're talking a lot of money for this kind of clean and calibration action - but you'd have to ask them.

In any case, its good to hear that the NEX does that well wtih contrast focusing.

good luck, phil
12-24-2011, 02:38 AM   #11
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QuoteOriginally posted by philbaum Quote
I don't think there is a problem with AF accuracy deteriorating with age. I've had my K5 since Feb 2011, use it every coupla days, and i'm not seeing any deterioration of the AF accuracy. I also have not noticed AF deterioration with my K10 or K20.
What's your shutter count on your cameras? Mine is well over 20k on the K-5, and well over 30k on the K10D.

I'm asking because I suspect the deterioration is based on usage, rather than age of the camera. I've had my K-5 since Feb too.
12-24-2011, 03:27 AM   #12
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My K5 is so much off that I will have to send it in for adjustment. 5 month old, no abuse..., it is not age, it is what Pentax sells to you. Test shots on a perfect balck and white target for focus micro adjustment showed that the AF was right on only 70% of the time - on a perfect target...
Did you get the shim kit for the Katzeye screen? It is gonna take for ever adjusting the AF first and then the screen position. I am more likely to sell the K5 and try another one. If that does not work out, I will try a new brand.

A new Pentax camera could use a automatic 21 shot program to test focus micro adjustment and 3/5 shot focus bracketing program (Contax had something like that, long time ago).
12-24-2011, 03:49 AM - 1 Like   #13
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Big time deja vu, didn't we have this conversation almost a year ago? Except you where one of those stating that there wasn't a low light AF problem? (I could be wrong though as there where a lot of people involved in the low light AF incident. )
12-24-2011, 05:54 AM   #14
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Could it not be the Katz eye causing the focus issues?
12-24-2011, 06:13 AM   #15
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No, its not used during AF.
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