How to deactivate SDM and allow for screw drive autofocus with DA* 16-50mm f/2.8


clover

Link Posted 02/01/2013 - 10:35
I already post this in pentaxforums.com, but it seems that it is helpfull to post here :

For the 16-50mm

http://www.pentaxiste.org/pratique/depannage/article/how-to-deactivate-sdm-and-a...

For the 50-135mm

http://www.pentaxiste.org/pratique/depannage/article/how-to-deactivate-sdm-and-a...
Last Edited by clover on 02/01/2013 - 10:52

cabstar

Link Posted 02/01/2013 - 12:28
Why???

All those lenses will work with screw drive only bodies, if its to get around a broken SDM lens then repairs with the newer parts can be done fairly reasonably.

I don't see the point of this...
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Currently on a Pentax hiatus until an FF Pentax is released

Mike-P

Link Posted 02/01/2013 - 12:36
cabstar wrote:
Why???

All those lenses will work with screw drive only bodies, if its to get around a broken SDM lens then repairs with the newer parts can be done fairly reasonably.

I don't see the point of this...

You are still looking at well over £100 for an SDM repair?
If you haven't got the money then this at least gives you af capability. I believe that screw drive on these 2 lenses is also quite a bit faster than SDM ... I might even consider the 50-135mm again (and sell the Sigma 50-150mm) if I could bypass SDM.
No equipment list here but thanks for taking an interest. My Flickr

cabstar

Link Posted 02/01/2013 - 14:09
Last quote I had was around £125 and that was with the new upgraded parts

When I compared my 50-135 on an old k110d (screwdrive) to my GX20 focus speed there was very little difference in AF speed. I think the noise of screwdrive creates an impression of speed.

Here are some shaky videos I made at the time

Screwdrive

SDM
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

Mike-P

Link Posted 02/01/2013 - 14:17
cabstar wrote:
Last quote I had was around £125 and that was with the new upgraded parts

When I compared my 50-135 on an old k110d (screwdrive) to my GX20 focus speed there was very little difference in AF speed. I think the noise of screwdrive creates an impression of speed.

Here are some shaky videos I made at the time

Screwdrive

SDM

£125 is a lot to some people so screw drive is still better than manual focus. Also AF speed was "supposedly" much improved with the K-7/K-5 .. I know some of my screw drive lenses were/are faster on those 2 bodies when compared with the K10D.
No equipment list here but thanks for taking an interest. My Flickr
Last Edited by Mike-P on 02/01/2013 - 14:18

cabstar

Link Posted 02/01/2013 - 14:21
Didn't SDM speed also improve on the k-7 / k-5 too???
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

clover

Link Posted 02/01/2013 - 14:53
cabstar wrote:
Why???

All those lenses will work with screw drive only bodies, if its to get around a broken SDM lens then repairs with the newer parts can be done fairly reasonably.

I don't see the point of this...

I do understand your point of view. It is obvious That the Best choice is to repair the Lens, but there are many situations where you might consider bot using sdm .
For example, the cost of reparing, using a converter, the lack of time to sens the Lens for repair it, an already failed sdm, etc...

In thèse cases, thé double af possibilities of thé Lens might be usefull

Mike-P

Link Posted 02/01/2013 - 15:06
cabstar wrote:
Didn't SDM speed also improve on the k-7 / k-5 too???

If it did I never noticed it on the 50-135mm.
As I understand it the limiting factor (with regard to AF speed) of SDM lenses is the lens motor itself, hence why the 18-135mm (DC motor) is much faster
No equipment list here but thanks for taking an interest. My Flickr

clover

Link Posted 02/01/2013 - 15:22
As I noticed that very first producted 16-50mm have a slower but smoother SDM than latter ones. ( I had a very first 16-50mm avaible in France and since, I broke it, exchange for a second with SDM failure, repaired and I tried more than 5 16-50mm during a sale I made by spliting K20, 50-135 and 16-50mm before the price increasing tiume)

cabstar

Link Posted 02/01/2013 - 16:28
Mike-P wrote:
cabstar wrote:
Didn't SDM speed also improve on the k-7 / k-5 too???

If it did I never noticed it on the 50-135mm.
As I understand it the limiting factor (with regard to AF speed) of SDM lenses is the lens motor itself, hence why the 18-135mm (DC motor) is much faster

Is there a different motor in the 18-135 then???
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

cabstar

Link Posted 02/01/2013 - 16:31
clover wrote:
cabstar wrote:
Why???

All those lenses will work with screw drive only bodies, if its to get around a broken SDM lens then repairs with the newer parts can be done fairly reasonably.

I don't see the point of this...

I do understand your point of view. It is obvious That the Best choice is to repair the Lens, but there are many situations where you might consider bot using sdm .
For example, the cost of reparing, using a converter, the lack of time to sens the Lens for repair it, an already failed sdm, etc...

In thèse cases, thé double af possibilities of thé Lens might be usefull

Hmm the use of a teleconverter is a good idea for longer glass maybe the 300mm f/4
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

johnriley

Link Posted 02/01/2013 - 16:49
Quote:
Is there a different motor in the 18-135 then???

Yes, it uses a different DC motor.
Best regards, John

clover

Link Posted 02/01/2013 - 17:23
cabstar wrote:
clover wrote:
Quote:
Why???

All those lenses will work with screw drive only bodies, if its to get around a broken SDM lens then repairs with the newer parts can be done fairly reasonably.

I don't see the point of this...

I do understand your point of view. It is obvious That the Best choice is to repair the Lens, but there are many situations where you might consider bot using sdm .
For example, the cost of reparing, using a converter, the lack of time to sens the Lens for repair it, an already failed sdm, etc...

In thèse cases, thé double af possibilities of thé Lens might be usefull

Hmm the use of a teleconverter is a good idea for longer glass maybe the 300mm f/4

I sold my 300mm DA for a 300mm FA 4.5 so I can use AF with a converter.

I will try to get the lens rom from a 300mm as soon as I can

cabstar

Link Posted 02/01/2013 - 18:46
johnriley wrote:
Quote:
Is there a different motor in the 18-135 then???

Yes, it uses a different DC motor.

Is that unique to that lens John?
PPG Wedding photography Flickr
Concert photography

Currently on a Pentax hiatus until an FF Pentax is released

johnriley

Link Posted 02/01/2013 - 18:56
cabstar wrote:
johnriley wrote:
Quote:
Is there a different motor in the 18-135 then???

Yes, it uses a different DC motor.

Is that unique to that lens John?

Yes, I think so. I was actually expecting the new 18-270mm to be a DC motor as well, but that one is marked up as SDM.
Best regards, John
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