C100: Is the Sigma 50-150 2.8 HSM OS Parfocal?

I wouldn't call it sloppy construction so much as being a case of not being worth the effort for AF lenses. The tolerances are extremely tight. Tight enough that a change in air temperature would throw off the back focus. I shimmed my 70-200 II with about 0.2mm to get it to being close to being parfocal. I got my 24-70L to be parfocal by just slightly turning the back screws on the mount. Sometimes, it is just impossible. My 16-35 II is parfocal at the far and widest ends but not in the middle due to the way the front elements shift while zooming.
 
Tim Nitsch said:
Mine was always pretty smooth, not cine-lens smooth obviously, but smooth enough to easily pull focus with out needing a follow focus, definitely not what your experencing.
In terms of stiffness, It was pretty stiff when I first got it, but has since loosened up and while it's still a little stiffer than my 24-105, I'm having no issues with it at all.
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Well yeah, my standards are pretty high. My issue with it is that I can't really focus with two fingers. Recently tried the old Sigma 50mm 1.4 and that was the same - they feel like they have a bit of texture to them, which generates friction. On the other hand, I tried a Sigma 70-200 at a store, a lens with exactly the same housing, and that was fine.

Looks about the same as what this guy is experiencing at about 1:15: https://www.youtube.com/watch?v=f2Z4Z5OGX-8
You can see him having to apply some pressure and hear the friction.
 
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I had a Sigma 18-35 that had a very tight feeling focus ring. My older version of the 50-150 and 30 f/1.4 were also somewhat tight feeling versus Canon lenses. I think it is just Sigma's design of their MF/AF clutch.
 
My own 18-35 is fine in comparison to the 50-150. It's not the best, but certainly a lot more manageable - easy to focus with two fingers from below. Probably because the ring is wider.
 
mhood said:
Until you put that lens on a different camera. We used to swap ENG lenses at will and after a short back focus procedure, they were totally parfocal.
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With a PL or Panavision mount, you can swap lenses to different cameras all day long (and we do) and not have any issues.

ENG cameras and lenses use an inferior mount and sloppy/cheap (comparatively) construction, and that is the problem.
 
Bubble said:
is it AF ? for those of you having the Dual Pixel AF.
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Yes, it does work using DP AF but only at f/2.8. Like most (if not all) non Canon lenses, as soon as you stop down AF doesn't work.

With that said, it does work pretty darn well. But a possibly issue is that the AF motor is kind of noisy and the mic can pick it up.
 
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