K-5 AF Problems

I have had my K-5 for a couple of months now and I am far from happy with its focusing especially in low light.

I have heard that some K-5s have an issue with this and users have returned their cameras for exchange. Is there a test that I can do to see if my camera has that problem, or whether it is just the poor focusing of the K-5 in general?

Also - are the Pentax lenses that have the focus motor built into them better at focusing than the other type. I don't mean quicker, I just mean will they overcome the low light focus problem?

Thanks, Jay.

It would be helpful if you could post an example image where there's been difficulty?

I don't usually take the photo John as the blooming thing won't lock on, there are some where I have taken the pic and they are still off focus even though I got the 'beep' and red light. I will post one shortly.

Have you updated your firmware to the latest version?

I do a lot of low light photography and have had no problems focusing with my K5. All cameras need a certain amount of light to achieve a focus lock, so if it's to dark the focus will hunt on any brand or make of camera.

"whether it is just the poor focusing of the K-5 in general? You either have a duff K5 or are doing something wrong in my opinion. what lenses are you using, have you tried?

As to lenses screw drive or motor drive, focusing is focusing, which ever method is used the focus should not be a problem. Low light focusing has nothing to do with motor or screw drive.

The test you could do, would be to get another brand of camera and test against the K5 in the same lighting conditions at the same time, you may find that both cameras have the same issue if there is not enough light for a focus lock.

Hi Fletcher8, thanks for your reply, I was referring to other posts on here where users have stated that they have had to return their K-5s due to an AF problem. One guy said he was on his 4th K-5 before it was fixed. I have updated my firmware when I bought the camera, about 2 months ago.

One problem I have is if the background is bright but the subject is dark such as in this photo below. I have the focus point on the model on a point it would normally focus on but it just goes from one extreme to the other on the focus motor without ever looking like locking on. In this case I was using a fill flash so the model was darker than you see here - but why if it was too dark didn't the focus adjust light kick in? Is it because the camera thinks than the scene is bright because of the background? The focus light comes on if all the scene is dark, yet not if the bit I am trying to focus on is dark and the rest bright. In the end I had to manually focus this shot.





The image below is the most frustrating - it wasn't even that dark, there is no flash on this image, just the constant lighting that was being used for the video shoot. This is one of the only images I got that was sharp, I was very disappointed with the K-5 in this instance.

I would use centre point only focus and focus on the eyes. I can't see any particular problem that I would anticipate with that, sop are you using Pentax lenses or something else? Is it the camera or the lens that is at fault?

John, it was set on centre point, or rather single point, it may have been on one of the other focus points but the camera was definitely on single point.

On the day I was using a Sigma 17-50mm 2.8 which I have had mixed results with and also a Tamron 70-300mm f4, which I know isn't a great lens but I am holding off on investing in a replacement in that range until I decide if I am sticking with Pentax or not. I had similar problems with both lenses.

Actually don't use centre point because you need to recompose and that actually will cause the focus to move backwards.
Use selective focus and make sure the focus point is on the eyes, that's the best way.

As for the focus error, i've no problem with mine but i've calibrated the AF have you?

I would try a Pentax lens to see what the difference is before assuming the camera is at fault. Depending on where you are, if you haven't got a Pentax lens then maybe a local shop will let you try one out.

It does sound like there's not enough light on the model for the AF to lock on, but the bright background is fooling the camera into thinking the AF light isn't needed. Have you tried throwing more light onto the model to assist focussing? Have you checked for front/back focussing on your lenses and adjuested accordingly? I know live view focussing is a bit cumbersome for this type of photography, but as a last resort, you can at least rely on contrast-detect AF to be 100% reliable.

I have Pentax and Sigma lenses including one SDM pentax lens (50-135). My First K-5 was terrible AF in low light problems, which installing FW1.03 didn't fix. I had to get it replaced.

My 2nd and 3rd K-5s were fixed by FW1.03. but when I say fixed they are still inconistant in light levels of EV2 and below


Assuming you've upgraded to FX1.03 and have then calibrated the AF of your lenses in good light then any low light AF problems will be down to the K-5's phase AF system. Trying a Pentax lens isn't going to tell you whether the camera is at fault or not as lenses from any brand can be calibrated in good light.


If you want accurate AF then use Lvie view and Contrast AF. Shouldn't be too much hassle in a Studio/model situation where you've got more time.

What is the exposure value for the non-flash pic you have posted aboce?

Awaiting exposure value to be sure, but it looks like there should be plenty enough light for the phase AF in the pic.

Might just be a duff K-5. I Hope not though.

Tried the sigma 100-300 f/4 indoors and it didn't locked on because of the low light but the DA*50-135 f/2.8 locked on without an hitch not sure it's the f-number or the focus speed that makes the difference, probably both.

Without sounding stupid, what is the K5 like in day light out side? Can I ask what mode you are shooting in, have you tried any other modes? Finally, is the diopter set correctly? Clutching at straws here i know, but just trying to think of what may be causing you an issue. Very difficult to be 100% but your K5 may be a duff one. Perhaps it's worth getting it checked out before your warranty expires!

Hope you get it sorted out!

Gareth

The exposure on the 2nd (non-flash photo) according to Lightroom data was 1/160th sec at f4.0 and ISO 1600

The lens was the Tamron 17-50mm f2.8 (not the Sigma as I mistakenly stated earlier)