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09-24-2012, 09:15 AM   #16
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QuoteOriginally posted by panoguy Quote
Just crazy good stuff. Sadly, I fully expect Sigma's "new" 120-300mm/2.8 with this function (also weather-sealed, with HSM & OS) will be just like the previous models and never be made with a K-mount on the back... We're just a small (and shrinking) marketshare, and I'm sure Sigma sees "no compelling business case" for Pentax users to buy a full-frame lens like that one. (And before you jump in - yes, I see the reasons to buy a lens like this for APS-C!)

I was at photokina yesterday and asked the guy at the Sigma booth, whether the 120-300mm will come in K-mount. He told me, that it indeed will come for Pentax! I repeated my question, pointing out, that in the past some lenses were said to come in K-mount but actually never showed up. He was aware of that, but assured me, that the new 120-300mm will come with Pentax mount. Of course, the Canon/Nikon/Sigma versions will be the first to be maufactured, but he was very sure about the Pentax version. I have no idea if the guy was really in the know, but that's what he told me.

09-25-2012, 02:24 AM   #17
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QuoteOriginally posted by lytrytyr Quote
With current bodies, it will be a challenge to determine the focus adjust needed at infinity.
A LensAlign or Lenscal won't be much use for that.

What would be really nice would be some focus adjust assistance in the firmware.
You have your camera and lens set up on a tripod,
with the center spot aimed at a contrasty target.
Enter "focus adjust assistance" in the menu.
The camera compares phase-detect and contrast-detect focus for the target,
and tells you what adjustment is needed.
Maybe it would be best using manual focus in LV, and when you think focus is spot on you just tell the camera to enter that value into the calibration database in the camera. If need it should be possible to manually override the value inb the database, but it will probably be needed 3-4 entries for each focal lenght range as calibration might differ depending on distance to target and focal length.

Not sure if it's a good thing to have micro adjustments available in the lens as it is difficult to know if it's the camera or lens that is badly calibrated. It's a risk it will create a big mess if using lenses on more than one camera. And it might also make it difficult to test used lenses when bying them. IMO it's better to only have micro adjustments available in the camera, but micro adjustment in the camera need to be more advanced than it has been so far.
09-25-2012, 02:45 AM   #18
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QuoteOriginally posted by Fogel70 Quote
Not sure if it's a good thing to have micro adjustments available in the lens as it is difficult to know if it's the camera or lens that is badly calibrated. It's a risk it will create a big mess if using lenses on more than one camera. And it might also make it difficult to test used lenses when bying them.
Good point.
Hopefully the lens software includes an "escape" option,
to reset everything to zero adjustment.
09-25-2012, 04:53 AM   #19
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QuoteOriginally posted by Fogel70 Quote
Not sure if it's a good thing to have micro adjustments available in the lens as it is difficult to know if it's the camera or lens that is badly calibrated.
Typically both camera and lens are out a bit (sometimes compensating each other, sometimes adding up to a noticeable proble).

That's why it is good to being able to calibrate camera and lenses individually. If you get it right, you can then exchange lenses between cameras without requiring individual lens settings on each camera.

The current camera-based "per lens" adjustments are a feeble substitute for what the Sigma lens-based system offers (and has no advantages whatsoever).

I believe that when you send in a lens for calibration then the service technicians do nothing else but software calibrate the lens (typically w.r.t. an individual camera which you are required to send in as well). In other words, the Sigma system empowers the user to do what has been hitherto reserved to service centers. That's just awesome!

No one is forced to use the system and I'd bet my bottom dollar that the software will have "reset to default values" option. As a matter of fact, there is a "Reset Adjustment" button visible in the screenshot panoguy provided.


Last edited by Class A; 09-25-2012 at 04:59 AM.
09-25-2012, 06:19 AM   #20
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QuoteOriginally posted by Class A Quote
Typically both camera and lens are out a bit (sometimes compensating each other, sometimes adding up to a noticeable proble).

That's why it is good to being able to calibrate camera and lenses individually. If you get it right, you can then exchange lenses between cameras without requiring individual lens settings on each camera.

The current camera-based "per lens" adjustments are a feeble substitute for what the Sigma lens-based system offers (and has no advantages whatsoever).

I believe that when you send in a lens for calibration then the service technicians do nothing else but software calibrate the lens (typically w.r.t. an individual camera which you are required to send in as well). In other words, the Sigma system empowers the user to do what has been hitherto reserved to service centers. That's just awesome!

No one is forced to use the system and I'd bet my bottom dollar that the software will have "reset to default values" option. As a matter of fact, there is a "Reset Adjustment" button visible in the screenshot panoguy provided.
The problem is that end users has not the same advanced tools to do the calibration. We can't separate focus errors from lens and camera, which most service centers can, as they have some reference tools to calibrate against.

Not sure how Sigma service centers do, but if sending in both Pentax body and lens to Pentax service center I would expect both to be calibrated separately, not only the lens.
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