[GLXLR]

As an experiment, can you put a piece of electrical tape over the SDM contact if there is such a thing? Then the body should think it's not an SDM lens?

Hmm. i might go try that!

*Edit*

I actually just found out this doesn't work for some reason. The lens simply refuses to focus when the SDM contacts are covered.

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Last edited by GLXLR; 07-24-2009 at 11:46 PM.

[Harry]

I've the 16-50 and 50-135 (both SDM) and the 70-200 and the 120-400 (both HSM). I really can't say there is a lot of difference in AF speed and/or lock. Most of it, as always, depend on the situation of the shot...

[krypticide]

My 16-50 is way faster at focusing than the Sigma 70-200mm. I wonder how the 70-200mm compares to the 50-135mm; perhaps it's similar, since people seem to gripe about AF speed. It definitely does take a while to go from minimum to infinity.

I had issues focusing the 16-50mm on my K20D during a recent shoot, but I was shooting almost into the sun with some heavy flaring. However, I suspect focus is more an issue of camera than lens motor (except for speed of ring movement).

[simico]

I don't have experience with Sigma HSM, but Pentax SDM disappoints me. I thought it would be not only quiet/silent, but also faster than screwdrive AF. Well, it's not! My kit lenses with screwdrive AF focus much faster than my 17-70 F4 SDM lens! With the kit lenses it's a very short (and loud) 'eeek', with the 17-70 it's a long (and quiet) 'tik tik tik tik' even for the slightest focus adjustment. Honestly, the kit lenses turn their focusing rings from minimum focus distance to inifinity (180 degree turn) faster than the 17-70 (only 45 degree turn!! btw that makes manual focusing nearly impossible and focusing ring/quick-shift system totally useless on this lens). I'm thinking about selling this lens and I'll avoid other SDM lenses for sure.

[Jonson PL]

i've been looking into sigma hsm lenses and so far i've seen announcements of them for the pentax mount but no 1st-hand reviews whatsoever of released lenses.

this is the one i am interested in:
Sigma - Lenses

Sigma's Note: "For Pentax mount, if the camera body does not support HSM, auto focus will not be available." so it will definitely uses HSM...

Thanks

I have two SDM lenses (16-50 and 50-135) and I tried the Sigma HSM 150-500 (due to their sponsoring and loaning lenses to the East-Coast Gathering put on by BrendanPK at the Blackwater wlp - thanks Sigma!). It wasn't a very good comparison really due to the shear size differences in the lenses. I have to say that the Sigma was buttery smooth and silent in it's focusing but was rather slow compared to my SDM lenses. But it's a huge lens and size alone could account for the difference. I was also using it on a K10D.

Now I have to say that my SDM lenses on my K-7 are soooo much faster, and when I shoot both cameras in the same shoot, both with SDM lenses, the one on the K10D feels very slow. So I'm itching to try that 150-500 on my K-7 now to see how much faster to focus it might be. I really really liked that lens. I want to buy one.

And good to hear that SDM speed, has also improved on K7

[netuser]

There were several of us on another thread discussing SDM and this odd behaviour it will sometimes show. It just hangings up and won't focus. The contrast is good and the light fine. The lens just refuses to focus. I'm not the only one that has had this issue. It doesn't happen often and there's no rythm to it. Ring motors certainly are more powerful and that may be the difference. As for the 4 bodies I have and good selection of lenses. The cameras have no issue with all my other glass.

Interestingly the *istD is screw drive only and the DA*16-50mm never hangs up on that body. Only on my other SDM enabled bodies.

Can you point me to this thread ?

I got a new DA*300 last week.
I mounted the lens on k20d and everything was perfect.
Today was checking the gear for some shooting tomorrow and when powered up DA*300 stoped working with SDM and only works with screw on k20d.

I take the lens out, clean contacts and same damn

[Peter Zack]

I can't remember the thread. it was unrelated but over 5-6 posts a couple of us were just saying that SDM seems to have a mind of it's own. Sorry I should have linked the thread. But there was nothing earth shattering there or solutions. Just that a few of us, me included, can't really figure these lenses out. My DA*16-50mm will lock on reasonablly fast in near darkness and then at 4 in the afternoon outside with a scene that has decent contrast, it just f**ks around as if it was pointed at a white wall. But on the *istD which is screw Drive only, it works just fine.

There seems to be no reason for this odd behavior and it's not consistant. One user did say that using the quick shift "wakes" his lens up and it then works normally.

Netuser, I'd send that 300mm back ASAP.

[netuser]

I can't remember the thread. it was unrelated but over 5-6 posts a couple of us were just saying that SDM seems to have a mind of it's own. Sorry I should have linked the thread. But there was nothing earth shattering there or solutions. Just that a few of us, me included, can't really figure these lenses out. My DA*16-50mm will lock on reasonablly fast in near darkness and then at 4 in the afternoon outside with a scene that has decent contrast, it just f**ks around as if it was pointed at a white wall. But on the *istD which is screw Drive only, it works just fine.

There seems to be no reason for this odd behavior and it's not consistant. One user did say that using the quick shift "wakes" his lens up and it then works normally.

Netuser, I'd send that 300mm back ASAP.

Hi

This morning I tried again on k20d and same thing, only screw.
Change the lens to k200d and I get SDM.

I made this changes a couple of time and sdm "only failed" one time on k200d.

Very odd.

I can't figure out what is happening.

Edit: And on screw this lens really sucks on k20d so much hunting and AF-C is not fast at all. On the k200d with sdm working everything is smooth and fast.

[Douglas_of_Sweden]

As an experiment, can you put a piece of electrical tape over the SDM contact if there is such a thing? Then the body should think it's not an SDM lens?

Doesn't work, unfortunately. Probably the SDM lens tell the camera "Hey, I'm a SDM lens" through the 7th A-contact. If the body has SDM it then deactivate the screw drive gear, so you get no AF at all. If it is a non-SDM body it doesn't care and use its only option, the screw drive.
If you try to get around this by covering both the SDM contacts and the 7th A-contact, the body will belive that it is a A-generation lens (only has the six contacts that codes min and max apperture), and since non of those lenses has any autofocus the camera dissengage both AF options.
It would be nice if Pentax gave a software option to select screw drive AF ahead of SDM...

[netuser]

Does any of you uses any SDM lens as screwdriven and it's working properly "as it should"?

Edit: Damn, why didn't I get Sigma 100-300mm APO EX DG F/4

[Big G]

I think the feeling of the focus speed will be dependent on what you're shooting.

I have the 17-70mm SDM and the focussing is fine, it's not overly quick but given that I use my 17-70mm as a walkabout and landscaping lens (which I manual focus anyway) then I am never aware of it not being that fast. However, I too have found that even in perfectly acceptable conditions (bright light and good constrast) that it won't lock focus at 17mm. I'm not sure why, but it has happened. However, when on holiday in France it was perfectly quick in the field and I never found it slow.

(here is my France set - France - a set on Flickr )

Now, what I will say is that I observe the same as the others on this forums - screw driven non-SDM lenses always seem pretty quick. My old kit lens and indeed my 10-17mm fish-eye both feel quite a bit nippier and lock focus much more quickly.

I haven't tried Sigma HSM, but I have a non-HSM lens (Sigma 100-300mm) and the focus speed is incredibly quick. A K-7 + Sigma 100-300mm would be a fantastic sports / wildlife combo.

[Jonson PL]

Hi

This morning I tried again on k20d and same thing, only screw.
Change the lens to k200d and I get SDM.

I made this changes a couple of time and sdm "only failed" one time on k200d.

Very odd.

I can't figure out what is happening.

Edit: And on screw this lens really sucks on k20d so much hunting and AF-C is not fast at all. On the k200d with sdm working everything is smooth and fast.

Sounds like it might be your K20 that is acting up. (Even if it turned to screw drive, then it should still have acceptable AF).

Have it checked out. You got one of the great STAR lenses, and is coupling it to a really good Pentax body. These things should simply work. It shouldn't be that you wish you had gotten the Sigma instead.

Does any of you uses any SDM lens as screwdriven and it's working properly "as it should"?

Edit: Damn, why didn't I get Sigma 100-300mm APO EX DG F/4

[danielchtong]

I got a new DA*300 last week.
I mounted the lens on k20d and everything was perfect.
Today was checking the gear for some shooting tomorrow and when powered up DA*300 stoped working with SDM and only works with screw on k20d.

I take the lens out, clean contacts and same damn

Even though off topic I have to thank you for your info'
I am the type that I hate lens with electroncis. There should be none and that contributes a lot to the longitivity of lenses. Tell me about the M* & A* lenses anyway.
I have DA200mm and I have been trying to find if one day my SDM is screwed, will be pop back to the screw drive . You just answer that .
Hope you can straighten out the SDM issue. Bud judging from those NiCan camps, the SDM is more like the first one to fail in a lens. Maybe we are used to foolproof screw drive AF lens. And my FA135mm still focuses faster than my DA200mm
Thanks for the info'

Daniel

[gawan]

There were several of us on another thread discussing SDM and this odd behaviour it will sometimes show. It just hangings up and won't focus. The contrast is good and the light fine. The lens just refuses to focus. I'm not the only one that has had this issue. It doesn't happen often and there's no rythm to it. Ring motors certainly are more powerful and that may be the difference. As for the 4 bodies I have and good selection of lenses. The cameras have no issue with all my other glass.

Interestingly the *istD is screw drive only and the DA*16-50mm never hangs up on that body. Only on my other SDM enabled bodies.

I have experienced this behaviour too with my 16-50, more often now than before. It is really annoying and happen more often in the long end, even in every second time, but without any consistent rule, as you mentioned!

I really consider reliability more important than small differences in speed!

[philbaum]

Hi

This morning I tried again on k20d and same thing, only screw.
Change the lens to k200d and I get SDM.

I made this changes a couple of time and sdm "only failed" one time on k200d.

Very odd.

I can't figure out what is happening.

Edit: And on screw this lens really sucks on k20d so much hunting and AF-C is not fast at all. On the k200d with sdm working everything is smooth and fast.

netuser,
That's really odd. I assume that when you put other autofocus lenses on the K20d, they work fine. Which sort of says that the AF circuit on the K20d is fine???

Have you installed the lastest ver 1.3 firmware on the camera?

Do you have different batteries in K200 vice the K20 (of course, i just remembered the K200D has aa batteries) This kind of implies that battery voltage is making a difference. Try a freshly recharged battery in your K20D, or perhaps a different one.

Also, in an old thread on dpreview, there was a discussion on the DA 50-135/16-50 about how a coupla guys fixed their SDM problems by just cycling their AF circuits by focusing on something close, then something far away, and then repeating it several times. Apparently the problem got less and less and then went away.

Regards my only SDM lens, the DA*300, i've not had any problems wtih the SDM AF. It was bought in 2008 in the fall and is working fine. No hangups ever. I just focused on a brick wall in shade inside my house but sunny outside. It focused fine and locked all the way to aperture F22 at 0.7" shutter in AV, AFS. I tried at each aperture