Turn off SDM on K-7

I searched the Forum but couldn't find the answer - at least not a complete one. I found a 16-50/2.8 Pentax lens for a very good price - but it has an issu with the SDM motor from time to time (known issue, the lens is 4 years old). So my question is: is there any chance to turn off the SDM on the K7 or K5 and use it only with the slot driven motor? Aparently there are some hacks but I do not really want to experiment with this. Thanks, Jiri

By preference, I would have the SDM fixed and then there's no problem. I don't think you can do this, but you could use manual focus. Alternatively, use an older body or a K10D without the 1.03 firmware upgrade.

I did a quick search in the K-7 manual (pdf) and it doens't mention it.
I'd say tweet someone in Pentax (dont' know whom though).
And try pentaxforums dot com (presume it's okay to mention another website).

I have always thought it would be a good idea for Pentax to include such a feature in a firmware upgrade but was told that if they were to do so then that would be more or less the same as admitting there is a problem with SDM on the 16-50mm and 50-135mm ... which they have never done despite there being plenty of people saying otherwise.

When inventing SDM why should anybody switch back to normal AF? No wonder that Pentax states nothing about this in the manual.

Thanks for the answers. I asked about the price of reparation and it would cost me about the same as the price of the camera (250 ChF) or even more so I let go. I'll perhaps wait for the Tamron equivalent without SDM (and its problems).

Btw on the pentaxforum there was a person that seemed to know something about disabling the SDM. He seemed to known quite a lot about the firmwares in general but unfortunately there was no simple guide as how to disable the SDM.

That said, I'm looking forward to a sunny weekend with all the autumn colours in the forest!

The answer is in your original post. If/when the SDM mechanism breaks, you ought to be able to use the alternative focussing method. For whatever reason, Pentax have decided not to make this a choice for us users. A bad choice in my opinion.

You can disable the SDM focussing by regressing to an older firmware version which is pre-sdm if your camera was made during the transitional period and it has a pre-sdm version of firmware, but it's not very easy to do.

Also I think the SDM lenses would probably focus a LOT quicker under screw drive. Infact if I could use screw drive with the 50-135mm I would sell my Sigma 50-150mm and buy another Pentax lens.

Well I just meant that Pentax wouldn't want their users to come back to normal AF, once the SDM was implemented. And of course they cannot admit they have problems with the SDM - well they can but don't want to. Which yields the same result, probably even worse than if they'd admit it.

Why should screw driven SDM lens focus faster than a non-SDM lens? Is the internal mechanics so different (less friction or whatever)?

can't you just put some electrical tape over the SDM contacts to make it default to screw drive?

No (You must enter a comment of at least 5 characters.)

It's highly likely that you could fool the body by insulating the 'data' pin, but I think that might just turn the lens into a MF one.