[Designosophy]

There was another thread regarding autofocus with one particular lens (Tamron 70-200 f/2.8), but I have this problem with multiple lenses. I wanted to see if anyone else has similar experiences with autofocus failure when using specific lenses on their K-01. Please post your list of successes and failures. Here's mine.

Problem lenses

Tamron SP 70-200 f/2.8. Complete failure at all focal lengths and distances. The camera goes through the focusing process and acts as if it's locked focus, but all photos are badly out of focus. Focus is accurate with this lens on my K-5 in both PD and CD AF modes.

Tamron SP 24-135 f/3.5-5.6. Complete failure at all focal lengths and distances. The camera goes through the focusing process and acts as if it's locked focus, but all photos are badly out of focus. Focus is accurate with this lens on my K-5 in PD AF mode, but not in CD AF mode.

Sigma 170-500 f/4-6.3. Complete failure at long distances at all focal lengths. The camera goes through the focusing process and acts as if it's locked focus, but all photos at distances larger than 15 feet are out of focus. At close range, focus is very close, but not perfect. This lens tends to front focus on my K-5 in PD mode. I haven't found a lens correction setting that resolves the problem. I haven't used it in CD mode on the K-5.

Good lenses

Pentax DA-L 55-300. Accurately locks focus, even in fairly dim light.

Pentax-F 50 f/1.7. Accurately locks focus, even in dim light.

Pentax-FA 50 f/1.4. Accurately locks focus, even in dim light.

Pentax-FA 77 f/1.8. Accurately locks focus, even in fairly dim light. This lens tends to back focus on my K-5 in tungsten-temperature light.

Tamron SP 28-75 f/2.8. Accurately locks focus, even in dim light.

Sigma EX 30 f/1.4. Accurately locks focus, even in dim light.

Sigma EX 50 f/1.4. Accurately locks focus, even in fairly dim light. Can occasionally have trouble in dim light and high-contrast situations.

Note: K-01 firmware is 1.01. I had the same problem with firmware 1.0, however. Focus lock zoom is turned off in all cases. It makes no difference whether it's on or off, but some have reported that turning it off solves the problem. Not so for me.

[Doundounba]

There have been at least two threads about this (one, two), but I think both were prior to firmware 1.01.

FWIW, my Sigma 17-70mm F/2.8-4.5 usually focuses quickly and accurately, even in pretty low light (shooting at 17mm, F2.8, 3200 iso and around 1/15s for example), but occasionally hunts. When it happens it feels like the lens was decently close to focus, but the AF system "guesses" in the wrong direction and will go all the way to the end of the focus range, then come back and lock. Of course, if you point it at something that doesn't have any contrast (eg a uniform wall), then it tends to hunt quite a bit. I'm also running firmware 1.01.

[Steinback]

I installed the new firmware right after getting my body. My experience with a friend's Sigma 50mm f/1.4 HSM was different than yours, it just zips from one end of its focus throw to the other extremely quickly without ever locking on anything.

The other fast lenses I have tried were fine, including the F28mm f/2.8, screwdrive converted DA* 16-50mm f/2.8 and Sigma 24-70mm EX DG Macro. Slower lenses like the F 35-70 f/3.5-4.5 and DA 55-300 focus accurately but take somewhat longer to focus.

[Neil MacG]

I have only one lens that has SDM/HSM - the Sigma 120-400mm F4-5.6 APO HSM. The SDM/HSM does not work and as there is no Screw Drive AF on this lens it becomes manual only on the K-01.

All my other lenses with AF work just as well if not better than they ever did on my Samsung GX-10 (K10D clone) these include:

Pentax DA 18-55mm (Original K100D Kit lens)
Pentax DA 50-200mm (Original K100D Kit Lens)
Pentax DA 35 F2.4 (Really fast to focus)
Pentax SMC FA 28-80 F3.5-5.6 (Really fast to Focus)

Sigma EX DG 105mm F2.8 Macro
Sigma 28-105mm F2.8-F4
Sigma 18-200mm F3.5-6.3

Tamron 18-250mm F3.5-6.3
Sigma 28-90mm F3.5-5.6 Macro

Except where indicated I wouldn't say they AF really fast - but they are quite acceptable.

The only really slow to focus AF lens that I have on the K-01 is the Sigma 100-300mm F4.5-6.7.

Neil

[vonBaloney]

The other day my K-01 suddenly decided to stop the lens down to like f/8 and hold it there when for no reason whatsoever and so the screen was quite dark -- it was a manual focus 'A' lens, but if it did that on a AF lens it would surely fail focus. Had to restart the camera to have it snap out of it. The K-01 is unusual compared to the Pentax SLRs in that it does not open the lens up until you turn the camera on, whereas any of the SLRs hold the lens wide-open as soon as you mount it. Since I noticed this, I have caught it doing that one other time, and then caught my K-5 doing the same thing in live view. So this seems to be a quirk of the firmware or bad contact or something -- make sure your lens is actually wide-open when it is trying to focus...

[VaderSS]

The Sigma 8-16mm focuses properly, almost every time, but often the camera won't release the shutter. I set it to release the shutter without a focus lock and it works fine.

EXIF data doesnt show the focal length below 10MM. It just shows 0 below 10.

[Designosophy]

There have been at least two threads about this (one, two), but I think both were prior to firmware 1.01.

FWIW, my Sigma 17-70mm F/2.8-4.5 usually focuses quickly and accurately, even in pretty low light (shooting at 17mm, F2.8, 3200 iso and around 1/15s for example), but occasionally hunts. When it happens it feels like the lens was decently close to focus, but the AF system "guesses" in the wrong direction and will go all the way to the end of the focus range, then come back and lock. Of course, if you point it at something that doesn't have any contrast (eg a uniform wall), then it tends to hunt quite a bit. I'm also running firmware 1.01.

I did about 5 searches and couldn't find other threads quite like this, but thanks for posting those links.

The other day my K-01 suddenly decided to stop the lens down to like f/8 and hold it there when for no reason whatsoever and so the screen was quite dark -- it was a manual focus 'A' lens, but if it did that on a AF lens it would surely fail focus. Had to restart the camera to have it snap out of it. The K-01 is unusual compared to the Pentax SLRs in that it does not open the lens up until you turn the camera on, whereas any of the SLRs hold the lens wide-open as soon as you mount it. Since I noticed this, I have caught it doing that one other time, and then caught my K-5 doing the same thing in live view. So this seems to be a quirk of the firmware or bad contact or something -- make sure your lens is actually wide-open when it is trying to focus...

The K-01 partially closes the iris in really bright situations to protect the sensor. I imagine yours got stuck in that partially closed state. Since it happened on both your K-01 and your K-5, I'd suggest that maybe it's the lens. You might check the aperture lever to make sure it's not slightly bent or something.

The Sigma 8-16mm focuses properly, almost every time, but often the camera won't release the shutter. I set it to release the shutter without a focus lock and it works fine.

EXIF data doesnt show the focal length below 10MM. It just shows 0 below 10.

I don't know about the shutter release issue, since I always keep mine in release priority mode, but I've heard that same EXIF issue with the 8-16 on other bodies.

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Last edited by Designosophy; 01-28-2013 at 06:31 AM.

[Na Horuk]

Pentax primes AF great, almost as fast as on a DSLR (on static objects), with the added bonus that you are not confined to AF points.
DA L 50-200mm:
I had some problems with my DA L 50-200mm, but the firmware update improved it a lot, went from "almost unusable" to "I can live with that."
DA L 18-55mm: works well, even in dim light.

I don't think the DA 40mm XS and DA 35mm f2.4 even need to be mentioned - they focus fast and accurately.
I can't contribute much more than that, I tend to use manual primes on the K-01.

[vonBaloney]

The K-01 partially closes the iris in really bright situations to protect the sensor. I imagine yours got stuck in that partially closed state. Since it happened on both your K-01 and your K-5, I'd suggest that maybe it's the lens. You might check the aperture lever to make sure it's not slightly bent or something.

Aha. It was different lenses. Have only seen this (that I noticed) when doing some tabletop photography -- I could have been shining the light right into the lens at some point. But it did definitely get stuck (as I was able to point the camera at my face away from the light and clearly see the aperture stopped down) after I was trying to focus and I noticed the screen was very noisy and the gain seemed pumped way up. I will keep an eye on it.

[BigMike]

So is it correct that all Sigma lenses with HSM will not auto focus with the K01?

[dualie]

I have only one lens that has SDM/HSM - the Sigma 120-400mm F4-5.6 APO HSM. The SDM/HSM does not work and as there is no Screw Drive AF on this lens it becomes manual only on the K-01.
Neil

So is it confirm that SDM lens will revert to screw drive on a K01?

[post_eos]

So is it correct that all Sigma lenses with HSM will not auto focus with the K01?

No. Mine focuses just fine, but with the occasional hunting mentioned by others above. No worse than with my K10D.

[Designosophy]

So is it correct that all Sigma lenses with HSM will not auto focus with the K01?

My Sigma 50 f/1.4 has HSM and it focuses quite well on the K-01.

[vonBaloney]

My Sigma 8-16 focuses on the K-01, but often wrongly, but it does the same on the K-5 in either PD or CD mode. Just the nature of an extreme wide-angle, I think -- depends on the details of the thing I'm pointing at. It does ok on my other lenses unless they get up to f/6.3 or greater on the long end of a zoom -- then it is hit or miss. I mostly manual focus with it, though.

[Medium FormatPro]

s it correct that all Sigma lenses with HSM will not auto focus with the K01

Incorrect