Pentax DA* 60-250mm autofocus: an exercise in frustration

bwDraco · 02-12-2017, 04:27 PM - **1 Like**

Originally posted by xinu

I seem to be having a similar if not the same problem as the OP with my 60-250 mounted to a K1.

When first mounted after some time off camera, I can't turn the focus ring and the K1 won't operate the SDM. Switching the lens to MF doesn't free the focus ring. When I take the lens off the camera the focus ring will turn freely. Off camera, if I move the focus to infinity and remount, the SDM will slowly step the ring to minimum focus and remain in that state. This is very strange behaviour since the SDM is functioning but only in one direction. After several mount/unmount attempts the focus starts to function, SDM operates normally and the quick shift works. I'm trying to find the secret sauce sequence to get this lens to work without the frustration of continuous mounting and cursing.

Does the camera need focus lock to enable quick shift? And/or does the camera somehow sense a SDM focus problem and for some reason won't release the clutch on the screw drive to manually focus?

Unfortunately I don't have my K7 with me to test it on that.

Yes, it is the same issue.

Apparently, a bit of tension on the screwdrive AF coupler will cause the focus ring to lock as if it was screwdrive focusing. This lock normally exists only to prevent movement of the focus ring from interfering with screwdrive AF, and is necessary to ensure that the focus ring does not rotate during AF operation. It is intended that this lock disengages when AF is complete. However, on modern bodies with SDM support, this lock can jam the SDM as well, causing autofocus to fail. This mechanism can also cause sluggish SDM performance by unnecessarily adding friction.

Draco

xinu · 02-12-2017, 04:55 PM

So this not a SDM problem but some type of deficiency with the body's screw drive coupler control that is preventing SDM to operate?

bwDraco · 02-12-2017, 05:04 PM

Originally posted by xinu

So this not a SDM problem but some type of deficiency with the body's screw drive coupler control that is preventing SDM to operate?

I'd probably say it's a combination of factors, but the camera body should not be one of them. I'm getting the impression that poor lubrication in the focusing helicoid is a factor as well; excessive friction will degrade AF performance and make the focus ring harder to turn than it should be. This is in addition to the problems the hybrid screwdrive/SDM mechanism has. (I'd say the latter is the main issue, though.)

Draco

**UncleVanya** · 02-13-2017, 06:36 PM

Are you back button af users by any chance?

bwDraco · 02-13-2017, 10:10 PM

I've been shooting with back-button AF for quite a while now. I'm not sure how this would be related to the issue, though...

Draco

**UncleVanya** · 02-13-2017, 10:54 PM

Originally posted by bwDraco

I've been shooting with back-button AF for quite a while now. I'm not sure how this would be related to the issue, though...

Draco

I'm not and perhaps due to the way I hold my camera I don't move the focus ring while autofocus is engaged. I'm trying to determine differences that may explain why your experience is vastly different from everyone I know personally. I have tried back button af and on the k3 I haven't loved it ergonomically. It feels more awkward and I found myself supporting the long lenses differently.

It is just a question that came to mind because of this. .

xinu · 02-14-2017, 09:08 AM

I'm a back button focus type but I can't see how that would be related to the problem we're having. The 60-250 lens will not focus period. Not manually or SDM driven auto focus. The focus ring on the lens will not move when mounted on the camera.

I'd like to know if anyone has any troubleshooting ideas. It's a terrific lens and I'd like to fix or at least find reasonable work around for the problem.

**SunValley** · 03-20-2017, 06:26 PM

This is too weird! I just ran into the same problem but with my DA* 16-50! When I mount my 16-50 on my K-30 with body AF switch in either AF.S or C the focus ring with only focus in one direction and get stuck at closest focus. If I flip the body AF switch to manual I have manual focus alright, if I switch back to AF.S or C, AF works fine! So far I haven't been able to reproduce this with my K-5, AF works fine with it.

Really don't know what to make of it, I guess I'll call Sun Camera Service in Toronto and see if they have seen anything of that sort. If I learn anything I'll post it here.

xinu · 03-26-2017, 03:20 PM

Originally posted by SunValley

This is too weird! I just ran into the same problem but with my DA* 16-50! When I mount my 16-50 on my K-30 with body AF switch in either AF.S or C the focus ring with only focus in one direction and get stuck at closest focus. If I flip the body AF switch to manual I have manual focus alright, if I switch back to AF.S or C, AF works fine! So far I haven't been able to reproduce this with my K-5, AF works fine with it.

Really don't know what to make of it, I guess I'll call Sun Camera Service in Toronto and see if they have seen anything of that sort. If I learn anything I'll post it here.

What you're describing seems to be a different problem than I have with my 60-250mm. When the lens is mounted to body the focus ring will not turn manually (by hand). No change in behaviour when flipping AFS/C or lens AF/MF switches. I can sometimes get the lens's focus ring to operate by vigorously twisting the focus ring to infinity and back for a minute or so before mounting to the camera. Unfortunately I can't rely on it to always auto focus after the warmup. It will eventually get stuck again and into the bag it goes. To bad. It's relatively light with great image quality.

**SunValley** · 03-26-2017, 06:59 PM

Originally posted by xinu

What you're describing seems to be a different problem than I have with my 60-250mm

Indeed, but the similarities make me think they're somewhat related. Maybe mine will worsen into what you have. Have you tried the lens with a different body? My K-30 is at 46300 clicks and it seems to be part of the problem as the lens works fine on my K-5 and on a brand new K-50. The tech guy at Sun Camera wouldn't risk an explanation without seeing the lens. Understandable.

frogfoot · 03-27-2017, 12:39 AM

Originally posted by bwDraco

Too bad there's no way to disable the SDM and fall back on screwdrive focusing...

There is a way. Mine is converted to screwdrive only.

**UncleVanya** · 03-27-2017, 06:29 AM

Originally posted by frogfoot

There is a way. Mine is converted to screwdrive only.

Please explain how it was converted. I have several people who want me to convert their 60-250's and I have found zero evidence anywhere of a songle successful conversion. One person claimed a conversion but later recanted and admitted they were mistaken and the lens was erratic and not reliable in the converted mode.

frogfoot · 03-27-2017, 06:37 AM

Unfortunately I don't know how to do it. When SDM in my 60-250 died, I went to repair service, and they offered me two options: to replace the motor for about $300 or convert it do screwdrive only for about $50. I chose the latter.

normhead · 03-27-2017, 06:39 AM

I'm going on five years with mine, it's been dragged and banged over portages in pelican cases and back packs, dropped 5 times, the last time resulting in a visit to the service centre and replacing 3 of the seals. It never stopped working. Even when it was hard to turn the zoom ring after the last drop, it still worked flawlessly. I'm just not a person who babies his gear. So personally, I'm mystified,

If you've had 5 units, my guess is, you just wear things out. You must use it a lot more than I do. How many exposures do you use the lens for before these kinds of things start happening? Mine has gone from being bought as a telephoto to becoming a favourite landscape and walk around lens on the K-1.

The AF isn't fast enough for a basketball game. I don't think any SDM lenses are.

**UncleVanya** · 03-27-2017, 06:40 AM

Originally posted by frogfoot

Unfortunately I don't know how to do it. When SDM in my 60-250 died, I went to repair service, and they offered me two options: to replace the motor for about $300 or convert it do screwdrive only for about $50. I chose the latter.

Can you tell us who serviced it?

03-27-2017, 06:39 AM	#29
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	I'm going on five years with mine, it's been dragged and banged over portages in pelican cases and back packs, dropped 5 times, the last time resulting in a visit to the service centre and replacing 3 of the seals. It never stopped working. Even when it was hard to turn the zoom ring after the last drop, it still worked flawlessly. I'm just not a person who babies his gear. So personally, I'm mystified, If you've had 5 units, my guess is, you just wear things out. You must use it a lot more than I do. How many exposures do you use the lens for before these kinds of things start happening? Mine has gone from being bought as a telephoto to becoming a favourite landscape and walk around lens on the K-1. The AF isn't fast enough for a basketball game. I don't think any SDM lenses are. Last edited by normhead; 03-27-2017 at 06:45 AM.

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02-12-2017, 04:27 PM - 1 Like	#16
bwDraco Veteran Member Join Date: Jul 2010 Location: New York Photos: Albums Posts: 1,071 Original Poster	Originally posted by xinu I seem to be having a similar if not the same problem as the OP with my 60-250 mounted to a K1. When first mounted after some time off camera, I can't turn the focus ring and the K1 won't operate the SDM. Switching the lens to MF doesn't free the focus ring. When I take the lens off the camera the focus ring will turn freely. Off camera, if I move the focus to infinity and remount, the SDM will slowly step the ring to minimum focus and remain in that state. This is very strange behaviour since the SDM is functioning but only in one direction. After several mount/unmount attempts the focus starts to function, SDM operates normally and the quick shift works. I'm trying to find the secret sauce sequence to get this lens to work without the frustration of continuous mounting and cursing. Does the camera need focus lock to enable quick shift? And/or does the camera somehow sense a SDM focus problem and for some reason won't release the clutch on the screw drive to manually focus? Unfortunately I don't have my K7 with me to test it on that. Yes, it is the same issue. Apparently, a bit of tension on the screwdrive AF coupler will cause the focus ring to lock as if it was screwdrive focusing. This lock normally exists only to prevent movement of the focus ring from interfering with screwdrive AF, and is necessary to ensure that the focus ring does not rotate during AF operation. It is intended that this lock disengages when AF is complete. However, on modern bodies with SDM support, this lock can jam the SDM as well, causing autofocus to fail. This mechanism can also cause sluggish SDM performance by unnecessarily adding friction. Draco

02-12-2017, 04:55 PM	#17
xinu Junior Member Join Date: Oct 2009 Location: Eastern Ontario Posts: 34	So this not a SDM problem but some type of deficiency with the body's screw drive coupler control that is preventing SDM to operate?

02-12-2017, 05:04 PM	#18
bwDraco Veteran Member Join Date: Jul 2010 Location: New York Photos: Albums Posts: 1,071 Original Poster	Originally posted by xinu So this not a SDM problem but some type of deficiency with the body's screw drive coupler control that is preventing SDM to operate? I'd probably say it's a combination of factors, but the camera body should not be one of them. I'm getting the impression that poor lubrication in the focusing helicoid is a factor as well; excessive friction will degrade AF performance and make the focus ring harder to turn than it should be. This is in addition to the problems the hybrid screwdrive/SDM mechanism has. (I'd say the latter is the main issue, though.) Draco

02-13-2017, 06:36 PM	#19
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Are you back button af users by any chance?

02-13-2017, 10:10 PM	#20
bwDraco Veteran Member Join Date: Jul 2010 Location: New York Photos: Albums Posts: 1,071 Original Poster	I've been shooting with back-button AF for quite a while now. I'm not sure how this would be related to the issue, though... Draco

02-13-2017, 10:54 PM	#21
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by bwDraco I've been shooting with back-button AF for quite a while now. I'm not sure how this would be related to the issue, though... Draco I'm not and perhaps due to the way I hold my camera I don't move the focus ring while autofocus is engaged. I'm trying to determine differences that may explain why your experience is vastly different from everyone I know personally. I have tried back button af and on the k3 I haven't loved it ergonomically. It feels more awkward and I found myself supporting the long lenses differently. It is just a question that came to mind because of this. .

02-14-2017, 09:08 AM	#22
xinu Junior Member Join Date: Oct 2009 Location: Eastern Ontario Posts: 34	I'm a back button focus type but I can't see how that would be related to the problem we're having. The 60-250 lens will not focus period. Not manually or SDM driven auto focus. The focus ring on the lens will not move when mounted on the camera. I'd like to know if anyone has any troubleshooting ideas. It's a terrific lens and I'd like to fix or at least find reasonable work around for the problem.

03-20-2017, 06:26 PM	#23
SunValley Site Supporter Join Date: Jun 2013 Location: Montreal, Canada Photos: Gallery \| Albums Posts: 573	This is too weird! I just ran into the same problem but with my DA* 16-50! When I mount my 16-50 on my K-30 with body AF switch in either AF.S or C the focus ring with only focus in one direction and get stuck at closest focus. If I flip the body AF switch to manual I have manual focus alright, if I switch back to AF.S or C, AF works fine! So far I haven't been able to reproduce this with my K-5, AF works fine with it. Really don't know what to make of it, I guess I'll call Sun Camera Service in Toronto and see if they have seen anything of that sort. If I learn anything I'll post it here.

03-26-2017, 03:20 PM	#24
xinu Junior Member Join Date: Oct 2009 Location: Eastern Ontario Posts: 34	Originally posted by SunValley This is too weird! I just ran into the same problem but with my DA* 16-50! When I mount my 16-50 on my K-30 with body AF switch in either AF.S or C the focus ring with only focus in one direction and get stuck at closest focus. If I flip the body AF switch to manual I have manual focus alright, if I switch back to AF.S or C, AF works fine! So far I haven't been able to reproduce this with my K-5, AF works fine with it. Really don't know what to make of it, I guess I'll call Sun Camera Service in Toronto and see if they have seen anything of that sort. If I learn anything I'll post it here. What you're describing seems to be a different problem than I have with my 60-250mm. When the lens is mounted to body the focus ring will not turn manually (by hand). No change in behaviour when flipping AFS/C or lens AF/MF switches. I can sometimes get the lens's focus ring to operate by vigorously twisting the focus ring to infinity and back for a minute or so before mounting to the camera. Unfortunately I can't rely on it to always auto focus after the warmup. It will eventually get stuck again and into the bag it goes. To bad. It's relatively light with great image quality.

03-26-2017, 06:59 PM	#25
SunValley Site Supporter Join Date: Jun 2013 Location: Montreal, Canada Photos: Gallery \| Albums Posts: 573	Originally posted by xinu What you're describing seems to be a different problem than I have with my 60-250mm Indeed, but the similarities make me think they're somewhat related. Maybe mine will worsen into what you have. Have you tried the lens with a different body? My K-30 is at 46300 clicks and it seems to be part of the problem as the lens works fine on my K-5 and on a brand new K-50. The tech guy at Sun Camera wouldn't risk an explanation without seeing the lens. Understandable.

03-27-2017, 12:39 AM	#26
frogfoot Forum Member Join Date: Apr 2011 Location: Moscow Posts: 70	Originally posted by bwDraco Too bad there's no way to disable the SDM and fall back on screwdrive focusing... There is a way. Mine is converted to screwdrive only.

03-27-2017, 06:29 AM	#27
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by frogfoot There is a way. Mine is converted to screwdrive only. Please explain how it was converted. I have several people who want me to convert their 60-250's and I have found zero evidence anywhere of a songle successful conversion. One person claimed a conversion but later recanted and admitted they were mistaken and the lens was erratic and not reliable in the converted mode.

03-27-2017, 06:37 AM	#28
frogfoot Forum Member Join Date: Apr 2011 Location: Moscow Posts: 70	Unfortunately I don't know how to do it. When SDM in my 60-250 died, I went to repair service, and they offered me two options: to replace the motor for about $300 or convert it do screwdrive only for about $50. I chose the latter.

03-27-2017, 06:40 AM	#30
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,404	Originally posted by frogfoot Unfortunately I don't know how to do it. When SDM in my 60-250 died, I went to repair service, and they offered me two options: to replace the motor for about $300 or convert it do screwdrive only for about $50. I chose the latter. Can you tell us who serviced it?