Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
10-05-2019, 07:56 PM   #16
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
QuoteOriginally posted by JimJohnson Quote
It's really fast and easy. Move the switch on the lower left side of the mirror box to the MF position.

Partly I'm posting to be educated. Why would you want to disable SDM driven AF?
Because there are 5 lenses that have both SDM and screw drive. When SDM fails on these they don't automatically use screw drive, you have to trick the camera into thinking the lens lacks SDM by reprogramming the lens rom.

10-06-2019, 05:03 AM   #17
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,771
QuoteOriginally posted by UncleVanya Quote
Because there are 5 lenses that have both SDM and screw drive. When SDM fails on these they don't automatically use screw drive, you have to trick the camera into thinking the lens lacks SDM by reprogramming the lens rom.
Okay, got it. "When" not "If". And twigging the software is cheaper than repairing or replacing the lens. I'm sure somebody has an answer to this, but why not just dab a little insulating lacquer on the SDM contacts on the lens? I think this is the power and one of the data pins. With no power/data connection to the body, wouldn't the lens automatically use the screw drive? (become a KAF mount rather than a KAF2)
10-06-2019, 09:28 AM - 1 Like   #18
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
QuoteOriginally posted by JimJohnson Quote
Okay, got it. "When" not "If". And twigging the software is cheaper than repairing or replacing the lens. I'm sure somebody has an answer to this, but why not just dab a little insulating lacquer on the SDM contacts on the lens? I think this is the power and one of the data pins. With no power/data connection to the body, wouldn't the lens automatically use the screw drive? (become a KAF mount rather than a KAF2)
Disabling the power has no effect on the camera using screw drive. That "fix" was first tried many years ago with zero effect.

---------- Post added 10-06-19 at 12:35 PM ----------

Also to be fair, quite a few SDM lenses work fine and never die in normal use. It isn't clear what percentage of the lenses fail or how frequently. Some of the examples of these lenses however have failed more than twice... .
10-06-2019, 10:48 AM   #19
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,771
It looks like the KA2 mount has one more data pin near the edge of the flange than the KA mount. I'm not surprised that power only doesn't do it. But bet insulating that extra pin would. On the other hand, it might turn the lens into a non-AF KA lens too.

10-06-2019, 10:51 AM   #20
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
QuoteOriginally posted by JimJohnson Quote
It looks like the KA2 mount has one more data pin near the edge of the flange than the KA mount. I'm not surprised that power only doesn't do it. But bet insulating that extra pin would. On the other hand, it might turn the lens into a non-AF KA lens too.
You are hashing old ground. I suspect the detailed discussions are still on the forum but I think you are correct in thinking that disabling the data pin simply renders the lens like an M series. Not a solution I would want to use.
10-06-2019, 12:22 PM   #21
Loyal Site Supporter
Loyal Site Supporter
JimJohnson's Avatar

Join Date: Jan 2012
Location: Summer:Lake Superior - Michigan Winter:Texas Hill Country
Photos: Gallery
Posts: 2,771
You would have to insulate ALL the data pins to turn a lens into a K (M) mount. A number of the pins communicate the lens' aperture range to the body for the 'A' setting. I was suggesting insulating only the additional data pin that appeared with the KA2 mount along with the power contacts.

None the less, point taken. This topic has likely been beat to a dead horse elsewhere in the Forum.
10-06-2019, 02:46 PM   #22
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
QuoteOriginally posted by JimJohnson Quote
You would have to insulate ALL the data pins to turn a lens into a K (M) mount. A number of the pins communicate the lens' aperture range to the body for the 'A' setting. I was suggesting insulating only the additional data pin that appeared with the KA2 mount along with the power contacts.

None the less, point taken. This topic has likely been beat to a dead horse elsewhere in the Forum.
The other pins are not "data" driven in that they only encode the static aperture information in a way that is passively read by which are shorted and un-shorted. There is no active communication over any of the pins other than the 1 pin in question. Without the 1 pin, no af and no focal length info etc. The lens could be considered a KA rather than a K or M lens I guess. I forget this because I have had some modern FA lenses that died in a such a way they became M series (A type automation no longer read and no AF).

10-06-2019, 04:05 PM   #23
Veteran Member




Join Date: Jan 2012
Location: United States
Posts: 793
QuoteOriginally posted by JimJohnson Quote
It's really fast and easy. Move the switch on the lower left side of the mirror box to the MF position.

Partly I'm posting to be educated. Why would you want to disable SDM driven AF?
Some times the SDM motor completely fails, which leaves a dead lens, converting to screw drive means you can still use the lens.

Other times like my 50-135 SDM, it would take 3-6 mins to start focusing (which is a lifetime in the middle of a photoshoot), and I was tired of the song and dance I had to do to get it to awaken.


Finally, some people felt that screw drive is also slightly faster than the SDM focusing.
10-06-2019, 05:54 PM   #24
Site Supporter
Site Supporter
Ex Finn.'s Avatar

Join Date: Nov 2007
Location: Southern Maryland. Espoo. Kouvola.
Photos: Gallery | Albums
Posts: 7,960
QuoteOriginally posted by y0chang Quote
Finally, some people felt that screw drive is also slightly faster than the SDM focusing.
I might be in that camp also.
10-06-2019, 08:55 PM   #25
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
QuoteOriginally posted by Ex Finn. Quote
I might be in that camp also.
Having converted a lot of lenses... Some working at least partially I'm not so sure. My own working lenses were my first conversions. I never found them to be faster focusing but that's when the lenses were working as expected. As sdms age, then they seem to slow down and start focus hunting which makes them look slower than when they are working at their best.
11-15-2019, 10:01 AM   #26
New Member




Join Date: Nov 2018
Location: Singapore
Photos: Albums
Posts: 11
QuoteOriginally posted by y0chang Quote
Some times the SDM motor completely fails, which leaves a dead lens, converting to screw drive means you can still use the lens.

Other times like my 50-135 SDM, it would take 3-6 mins to start focusing (which is a lifetime in the middle of a photoshoot), and I was tired of the song and dance I had to do to get it to awaken.


Finally, some people felt that screw drive is also slightly faster than the SDM focusing.
My 16-50 sdm died after using less than 3 years & I didn't use it for 2 years. Then one guy in our local Pentax forum said he can disable the sdm & he used my K20 to do it. My 16-50 came back to life & I have been using it for the last 4 years
11-17-2019, 08:54 PM   #27
mlt
Site Supporter
Site Supporter




Join Date: Dec 2007
Posts: 1,159
QuoteOriginally posted by JimJohnson Quote
It's really fast and easy. Move the switch on the lower left side of the mirror box to the MF position.

Partly I'm posting to be educated. Why would you want to disable SDM driven AF?
To change the lens to screw drive AF when the SDM motor fails. Some have reported the screw drive Af s faster.
11-25-2019, 04:25 AM   #28
Veteran Member
dcpropilot's Avatar

Join Date: Mar 2010
Location: Vermont
Photos: Gallery | Albums
Posts: 941
Original Poster
Anyone know the newest camera that can be used to convert to screw drive? K-5 or K-7?
11-25-2019, 07:11 AM   #29
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 28,178
I know the k-5 works per thread reports. I'm not sure if it works without the use of pktether. I don't recall anyone ever mentioning converting using a k-7.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
drive, dslr, effect, k-3, k3, lens, lenses, pentax k-3, power, screw, sdm
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Anyone been able to find some more 16-85mm reviews/info? Conqueror Pentax SLR Lens Discussion 0 12-14-2014 09:47 AM
How to disable SDM on the lens ? lotech Troubleshooting and Beginner Help 9 05-24-2014 04:33 PM
The Pentax K-01 has been found to cure any unusual feelings in pants. crewl1 Pentax K-01 6 01-08-2014 11:40 AM
Has It Been Confirmed That The K-3 Will Accept UHS-I...? tabl10s Pentax K-3 & K-3 II 11 10-20-2013 12:21 PM
The K-3 finally has what I've been looking for in a DSLR. tigrebleu Pentax K-3 & K-3 II 34 10-09-2013 10:56 PM



All times are GMT -7. The time now is 05:19 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top