Sigma HSM K7 vs. K20D?

kenyee · 07-15-2009, 08:15 PM

Has anyone compared focus speed and lock reliability of Sigma HSM lenses (e.g., the 70-200/2.8 and 24-70/2.8) on the K7 vs K20D?

I know DA lenses are limited by the micromotor speed so there's no speed difference but screwdrive is a lot faster on the K7. Just wondering if there's any difference in speed w/ Sigma's real ring motors...

kenyee · 07-16-2009, 02:49 PM

No one w/ a K7 has a Sigma HSM lens? :-)

*GLXLR* · 07-16-2009, 03:27 PM

Originally Posted by kenyee

No one w/ a K7 has a Sigma HSM lens? :-)

Well it is a Pentax camera. What'd you expect?

I am sure though that SDM performance would mean the same for HSM.

*brecklundin* · 07-16-2009, 03:36 PM

actually HSM is a much more mature tech and is quite fast. I know it is maybe an order of magnitude (exaggerating...

) faster than my 50-135mm but I don't care as the IQ with that beastie is just supurb. I can worry about a faster focus drive lens once I buy a K7.

kenyee · 07-18-2009, 07:45 PM

FYI, Sigma HSM seems to have issues w/ Liveview contrast-detect AF on the K7:
K-7 CD-AF and Sigma 70-200mm HSM II: Pentax SLR Talk Forum: Digital Photography Review

ManuH · 07-18-2009, 08:16 PM

Originally Posted by kenyee

Has anyone compared focus speed and lock reliability of Sigma HSM lenses (e.g., the 70-200/2.8 and 24-70/2.8) on the K7 vs K20D?

I know DA lenses are limited by the micromotor speed so there's no speed difference but screwdrive is a lot faster on the K7. Just wondering if there's any difference in speed w/ Sigma's real ring motors...

The Sigma 70-200 f/2.8 II that I have now is working very fast. I'd say noticeably faster than the 50-135. The HSM can accelerate but SDM is mostly linear just like screw-driven AF. It also seems to be able to change direction faster.

For reliability I cannot say a lot, my copy is front focusing and even the AF correction is not strong enough on the K-7 (I'd wish they would allow for -20 to +20, I don't understand why they limit it to +/- 10). It's only an issue at f/2.8 and as a result at this aperture the pictures look softer than they should be. Otherwise the focusing seems consistent but a few times the K-7 would lock on a completely blurry picture (happens sometimes too with SDM BTW).

The only visible bug is that Liveview CD-AF doesn't work at all with this lens.

BTW I think SDM is also faster on the K-7 vs the K20D.

*brecklundin* · 07-18-2009, 08:23 PM

yup...and read this thread from post #148 unless of course you haven't read the whole thread just yet.
K7 busted sensor strikes production body

From reading the DPReview thread and here, is it possible that Pentax actually altered their end of the AF interface enough to induce issues with HSM lenses where no previously existed. Not intentionally but just the might have done a tad too much tweaking and broke compatibility. I sense a pattern between the sensor issue and this...I also sense there may be more than six K7's heading back to retailers soon. I think it is inherent upon Pentax to not break compatibility with 3rd party lenses and focusing systems. And if they did they need to make it plain and be up front. Face it, they are symbiotic.

kenyee · 07-19-2009, 10:11 AM

Originally Posted by brecklundin

I sense a pattern between the sensor issue and this

I'm puzzled. What pattern do you mean?
The horizontal/vertical line thing looks like a sensor readout bug to me...nothing related to HSM...

krypticide · 07-19-2009, 12:50 PM

Originally Posted by ManuH

The Sigma 70-200 f/2.8 II that I have now is working very fast. I'd say noticeably faster than the 50-135. The HSM can accelerate but SDM is mostly linear just like screw-driven AF. It also seems to be able to change direction faster.

Awesome, finally, someone can comment on the relative speeds of the 70-200mm HSM and the 50-135mm. The 70-200mm isn't particularly fast (to me), so I guess the 50-135mm is even slower than I'd want.

kenyee · 07-19-2009, 07:49 PM

Originally Posted by ManuH

The only visible bug is that Liveview CD-AF doesn't work at all with this lens.

Forgot to ask...did you let Sigma know about this issue? Seems like it's an HSM bug because someone else on DPR had the same problem...

*brecklundin* · 07-20-2009, 08:03 AM

Originally Posted by kenyee

I'm puzzled. What pattern do you mean?
The horizontal/vertical line thing looks like a sensor readout bug to me...nothing related to HSM...

Sorry I know I was not all that concise in my comment. I was on the edge of sleep when the idea hit me. What sort of came to me, is I doubt Pentax would break HSM compatibility as the 3rd party lenses help sell bodies and eventually Pentax lenses. I doubt Sigma changed anything on their end, though of the two I could see them deciding to drop Pentax mounts should there need to be a firmware upgrade/update to all current pentax mount. I mean if that it really was the goal of Pentax to break compatibility 'accidentally on purpose".

But what I really sense is with the, admitted by Pentax, heat related issue on the new sensor in the K7, is it not so much a flaw in the sensor but rather a heat issue in the body. Heating of components can cause inconsistent behavior or even failure in random fashion. What of the heat issue was affecting the AF signal by inducing noise in one of the circuits which control the AF. Yet at the same time, I sense that Pentax SDM lenses would suffer the same as Sigma HSM...but without any evidence of more widespread issues we won't know.

Sigma reverse engineers their interface for all their lenses and I have long suspected the newer versions can contain vastly different firmware from early copies but consumers will never know. but this would be where breaking the compatibility will require Sigma to either go back to the boards and mode their firmware for just one camera or they can just give up. Many Sigma lenses represent a price point threat to HoyaTax lenses, if eliminated from the equation someone somewhere might consider that a good idea...I doubt it is the case but it came to mine...so I was just 'typing out loud' but wasn't terribly complete.

And nope not a tinfoil hat sorta guy, I just never trust the visible motivation by corporations anymore. Especially those who have a well know reputation for attempting to not quite price fix but rather enforce minimum advertised prices as Hoya has done not long ago. This resulted in a rather confrontational situation with one of their vendors. And along the way the Hoya folks pretty much admitted the goal was to ensure all sellers were going to get the same price and not need to compete on price. It is an end around on existing regs as laws. And even might be illegal in a few states and probably all others in short order thanks to a Maryland Supreme court ruling that such agreements were illegal not just within the state of Maryland but also for web based companies doing business with buyer in Maryland...hence I have a jaundiced eye toward HoyaTax but that all needs to shake out...and also why I even considered the accidentally intentional break in compatibility should this spread to more lenses or just the lenses which compete with current Pentax models.

Sooo, maybe I do need a tinfoil hat and a bucket of Abilify after all hehehehe...or maybe it is just an unexpected issue with one, or a few, lens(es)...it happens...

ManuH · 07-20-2009, 08:14 AM

Originally Posted by kenyee

Forgot to ask...did you let Sigma know about this issue? Seems like it's an HSM bug because someone else on DPR had the same problem...

No, I'm returning the lens because I need the money anyway. That bug doesn't exist with Pentax lenses (SDM included). I guess Sigma will fix this issue at some point but I'm not really interested, this is not exactly the kind of lens for which I would use CD-AF anyway. I only tried CD-AF to compare the focusing accuracy with phase detect which was obviously off.

Originally Posted by krypticide

Awesome, finally, someone can comment on the relative speeds of the 70-200mm HSM and the 50-135mm. The 70-200mm isn't particularly fast (to me), so I guess the 50-135mm is even slower than I'd want.

Yes the 50-135 has never been an AF speed demon. That's also why I was interested by the Sigma in the first place.

kenyee · 07-20-2009, 12:32 PM

Originally Posted by brecklundin

What of the heat issue was affecting the AF signal by inducing noise in one of the circuits which control the AF. Yet at the same time, I sense that Pentax SDM lenses would suffer the same as Sigma HSM...but without any evidence of more widespread issues we won't know.

Yep...and exactly why it shouldn't be related...

I have no idea why Sigma HSM doesn't work w/ the K7's contrast detect AF, but I'm curious enough to email Sigma for an official response since Manu returned his lens. I'm thinking of getting a 24-70 next year, so it'd be nice to know that it does work properly on a K7...

*brecklundin* · 07-20-2009, 02:07 PM

Originally Posted by kenyee

Yep...and exactly why it shouldn't be related...

I have no idea why Sigma HSM doesn't work w/ the K7's contrast detect AF, but I'm curious enough to email Sigma for an official response since Manu returned his lens. I'm thinking of getting a 24-70 next year, so it'd be nice to know that it does work properly on a K7...

right...I agree completely. Just one of those things that runs through the brain (?) when a new device has issues in one area. Especially when that issue has already been officially, admitted as a heat issue by Pentax.

Kinda cool to have a company just come out and say "...oops, this is not right...we're gonna fix it soonest..." very refreshing actually.

He is hoping maybe you might just have an issue with the contacts on the lens. Something along those lines would be an easy fix...or even a fast trip to Sigma for a re-chip or firmware update.

It sure would be nice if Sigma had a way to update firmware on the user end. One day...after I'm dust they just might.

eagle · 07-21-2009, 05:42 AM

I use a Sigma HSM 50 -150mm f/2.8 lens. It focuses fast and accurate with regular phase detection AF (on the K-7), which I use.

Does not focus with contrast AF in Live View, which I don't use.

In the end, I'm happy. Although, I do like my Sigma, and would hope to see them continue to support the Pentax mount.