[Lowell Goudge]

A lot of these recent Sigma's (incl. HSM's) are said to be compatible with their existing TC's. I didn't think they would work because they lacked the HSM contact, but, again, that is the claim. Unless it's just Pentax that doesn't work for some reason.

It's impossible unless it also supports screw drive

[Class A]

I'm hoping to do a comprehensive comparison of the in-camera SR versus the in-lens OS (there's two settings for it).

I'm very interested to see these.
If you are hand-holding, you'll need to make lots of shots to get a chance of producing the same range of shake for each system. At the long end, a hand-holding replacement like a cushion or a super-cheap tripod might work. Such supports do not really reduce all vibrations from pressing the shutter release button, the mirror and the shutter, so they should still allow shake to occur that needs to be 'removed'.

Also, has sigma released an HSM TC for the pentax line yet, because the real interest I have would be to get to either 450F4 or 600F5.6 with this lens.

To the best of my knowledge there is no such HSM TC yet, but any TC with all contacts (including SDM/Power zoom) should do the trick, shouldn't it?

The camera will be fooled about the real focal length, but there are only so many contacts on a K-mount and if they are all passed through by a TC (there are such Kenko models, for example) then I don't see why it wouldn't work.

As third-hand information, I've heard that such TCs sometimes work with an HSM lens but sometimes cause problems. Unless the respective TCs are defect, I could only imagine that their conductivity might not be optimal for digital signals, but this is serious speculation.

[mel]

I'm very interested to see these.
If you are hand-holding, you'll need to make lots of shots to get a chance of producing the same range of shake for each system. At the long end, a hand-holding replacement like a cushion or a super-cheap tripod might work. Such supports do not really reduce all vibrations from pressing the shutter release button, the mirror and the shutter, so they should still allow shake to occur that needs to be 'removed'.

Um. Of course it'll be hand held. What's the point of an SR/OS system otherwise?

[DogLover]

That's silly: it's not like it's that hard to put a K-mount on a lens that costs more than some cars. "I would like to give you several thousand dollars if you'll do a little more engineering and machining."

"OK."

Silly or not, that's been their M.O. until very recently. I don't think they offered anything more than about $1500 in K-mount. It's probably not so much about physically attaching a different mount, it's more about inventory and distribution concerns.

[Class A]

Of course it'll be hand held. What's the point of an SR/OS system otherwise?

There is a difference between using the systems and testing them.

I was assuming that you don't have access to a professional shaking apparatus. You could use the latter to run through precisely defined vibration profiles which provide repeatable test conditions. With such an apparatus you wouldn't need heaps and heaps of shots.

When you hand-hold, conditions are anything but repeatable. So you'll need a lot more shots to handle the large variability such a test involves. If you only take a few shots, you might shake less on average with one system than with the other, have a big outlier with one system but not the other, etc. You'll make observations that say nothing about the systems but everything about the differences in how you happened to use them.

That's why I suggested you might want to look into something that is a bit more controlled than hand-holding. Your test results could then actually say something about the differences between the systems.

I'm not saying I have a recipe for simulating hand-holding in a more controlled manner -- you'll have to ask falconeye about this -- but I remembered his "weak tripod" and "cushion" tests from his "shutter blur" analysis.

Yes, you can also get a significant comparison of the two system by using hand-holding, but you'll have to take more shots than you are probably interested into taking, analyse the blur quantitatively for each shot (e.g., with FocusMagic), and compare the resulting distributions. I thought you were probably not embarking on something like this.

[mel]

Okay then let me rephrase my original statement: I'm hoping to give the OS system a good "checking out" to see how it compares to the in-body SR, for me in my shooting ability, while hand-holding at various focal lengths and apertures.

There. Now I'm off the hook.

[Class A]

Now I'm off the hook.

You think...
No, no, all good.

Have fun with the lens. I wish I could play with such an interesting piece of glass as well.

[Lowell Goudge]

To the best of my knowledge there is no such HSM TC yet, but any TC with all contacts (including SDM/Power zoom) should do the trick, shouldn't it?

The camera will be fooled about the real focal length, but there are only so many contacts on a K-mount and if they are all passed through by a TC (there are such Kenko models, for example) then I don't see why it wouldn't work.

Note that reading direct info through the TC (as the present sigma TC's do, results in SR being set to the wrong Focal length.

Additionally, and this has been found on the K10D and K20D, the feed through of lens aperture without correction in the TC leads to exposure issues, the K10D with an F2.8 lens and 2x TC constantly over exposes by 1.3 stops.

It would be ideal to have a TC that corrects for focal length and aperture or have in camera support for such.

Lastly, while I am sure some of the old TCs from the power zoom days are reasonable quality, I would prefer th use a TC designed to work with sigma's longer lenses exclusively

[DogLover]

On DPReview's posting of the release of the new 50-150, the last bullet point listed says "compatible with Sigma EX DG APO Tele-Converters". This is an HSM (and OS) lens. On Sigma's own website the info page for the new 120-300 has as the last line of the paragraph "the addition of the optional APO tele converter produces an ultra telephoto zoom lens with AF". Now, I am aware of Sigma spreading mis-information in the past, but this is at least some evidence of compatibility. Unless there is something that prevents only Pentax from sharing this compatibility and they are forgetting about us again, which they have also done before. I know in the past, the TC's didn't work with HSM lenses, so have they changed something on these new lenses? Am I just missing something? I am genuinely asking. I have called Sigma on issues before and have always gotten the sense that the person who answers the phone (and the people she goes to ask) don't have much of a clue.

[jolepp]

The REAL new bigma: Sigma 120-300 f/2.8 APO EX DG OS HSM f/PNTX 136109 B&H Photo ...

Ouch ... seeing the price was like a kick in the groin except the pain still lingers in the general purse area

[thirdofthree]

On Sigma's own website the info page for the new 120-300 has as the last line of the paragraph "the addition of the optional APO tele converter produces an ultra telephoto zoom lens with AF".

This may help: Sigma TC compatibility chart.

[DogLover]

This may help: Sigma TC compatibility chart.

Thanks for the link but that is an old chart that doesn't include any of the new versions of these lenses. I suspect that it is again a case of Pentaxians being left out, just as in the past.

[Lowell Goudge]

On DPReview's posting of the release of the new 50-150, the last bullet point listed says "compatible with Sigma EX DG APO Tele-Converters". This is an HSM (and OS) lens. On Sigma's own website the info page for the new 120-300 has as the last line of the paragraph "the addition of the optional APO tele converter produces an ultra telephoto zoom lens with AF". Now, I am aware of Sigma spreading mis-information in the past, but this is at least some evidence of compatibility. Unless there is something that prevents only Pentax from sharing this compatibility and they are forgetting about us again, which they have also done before. I know in the past, the TC's didn't work with HSM lenses, so have they changed something on these new lenses? Am I just missing something? I am genuinely asking. I have called Sigma on issues before and have always gotten the sense that the person who answers the phone (and the people she goes to ask) don't have much of a clue.

I think it is a case of pentax supporting HSM much later than canikon, who have had it for some time now and the TCs for those mounts may have been compatible already.

[Jodokast96]

Note that reading direct info through the TC (as the present sigma TC's do, results in SR being set to the wrong Focal length.

Additionally, and this has been found on the K10D and K20D, the feed through of lens aperture without correction in the TC leads to exposure issues, the K10D with an F2.8 lens and 2x TC constantly over exposes by 1.3 stops.

It would be ideal to have a TC that corrects for focal length and aperture or have in camera support for such.

Lastly, while I am sure some of the old TCs from the power zoom days are reasonable quality, I would prefer th use a TC designed to work with sigma's longer lenses exclusively

Lowell, for the record I'm not trying to argue with you or say you are wrong. But I will offer an opposing viewpoint and let Mel (or anyone else) figure out for themselves, that I have never seen this overexposure you claim exists when using a TC. No need to go posting your chart, because like I said, I'm not here to argue about it and am not going to take the time to post real world pics, etc. I just don't feel it's anywhere near the issue you make it out to be.

[mel]

I don't have a TC but with just a few cursory snaps, chimping in camera, it seems that it overexposes with just the lens itself compared to what I am used to seeing using Pentax lenses. Or even my 70-200 (Sigma) for that matter. But again, this is just cursory. I have yet to have time to load the images into my computer to really look at them. They just look overly light unless I use the EV at minus about a full stop. But it's hard to tell on the back lcd and not pulling up the histogram (I really need to find some time here . . . ).

As an aside, my 18 year old son has dubbed the beast "Overcompensation."