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01-10-2015, 04:13 PM   #61
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QuoteOriginally posted by MadMathMind Quote
I don't think it can come directly from the lens. If it does, then the Pentax engineers had remarkable prophetic vision in to 1980s to include a parameter in lenses for something that wouldn't be developed for 20 years. More likely, the camera assembles this value from some collection of information provided by the lens.

It doesn't simply match with the actual focal length if the parameter is missing. I have different values for my F series 70-210 lens, which shouldn't be providing any SR parameter since it's 25 years old. The camera has to be creating this value from some combination of focal length, focusing distance, etc.
The F series lenses were the first ones to use the KAF mount with digital data transmission to the camera body,

01-10-2015, 05:07 PM   #62
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QuoteOriginally posted by kh1234567890 Quote
The F series lenses were the first ones to use the KAF mount with digital data transmission to the camera body,
Yes. But if you're saying the lens sends these numbers...
focal length
aperture
...
SR focal length

I don't believe it because why in 1985 or whatever would there be a parameter called SR focal length? And actually, this SR focal length cannot come from the lens. I just checked it on a 200mm lens M series lens. I had input 200mm as the focal length into the camera. It lists the SR focal length as...204mm. Now where did it get that if the lens transmits absolutely no information? There's no option for 204mm. And 200mm is a possibility because I've gotten that with my Sigma 70-200 before.

So, I conclude that the SR focal length parameter is calculated by the camera from the actual focal length and....something else. But what? Clearly, the lens itself doesn't play a role in the process because if it did, we should get the same number for an M lens that the camera was told--or we'd get nothing at all and stabilization wouldn't work for pre-F series lenses. But it does work. So...what on earth does the camera do to get this parameter?
01-10-2015, 06:03 PM   #63
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QuoteOriginally posted by MadMathMind Quote
Yes. But if you're saying the lens sends these numbers...
focal length
aperture
...
SR focal length

I don't believe it because why in 1985 or whatever would there be a parameter called SR focal length? And actually, this SR focal length cannot come from the lens. I just checked it on a 200mm lens M series lens. I had input 200mm as the focal length into the camera. It lists the SR focal length as...204mm. Now where did it get that if the lens transmits absolutely no information? There's no option for 204mm. And 200mm is a possibility because I've gotten that with my Sigma 70-200 before.

So, I conclude that the SR focal length parameter is calculated by the camera from the actual focal length and....something else. But what? Clearly, the lens itself doesn't play a role in the process because if it did, we should get the same number for an M lens that the camera was told--or we'd get nothing at all and stabilization wouldn't work for pre-F series lenses. But it does work. So...what on earth does the camera do to get this parameter?
What you see in the MakerNotes of the EXIF is whatever the decoding program makers had decided that a particular byte or sequence of bytes that the camera put there means. There is no easy way of knowing what gets transmitted between the lens and the camera body through the data pin (it is a two way serial one wire comms), although the various patents do provide some clues. KAF and subsequent mount type lenses (F series onwards) use sliding contacts inside the lens barrel to read the focal length (for zooms) and the focus distance zone. The SR processor then uses this (again as described in the various patents) as input parameters (amongst others). If the lens does not send this information then the camera uses the manually set FL (as for lenses prior to the F series).

Sigma had to reverse engineer the lens-camera communication protocol, with limited success, as is always the danger with reverse engineering
01-10-2015, 07:23 PM   #64
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QuoteOriginally posted by kh1234567890 Quote
The SR processor then uses this (again as described in the various patents) as input parameters (amongst others). If the lens does not send this information then the camera uses the manually set FL (as for lenses prior to the F series).
But we know that's not quite it either because my M lens, which transmits nothing through its missing electrical contacts, gave me a SR focal length of 204. That's not even an input option (I told it 200mm). I can't believe the camera is measuring the focal length of the lens--if it could do that, then we'd never need to input any FL to being with.

It only seems to be this lens. And then only certain ranges of focal length. My Sigma 18-35 has its SR parameters correct, as does the Sigma 70-200 II I have.

01-11-2015, 09:20 AM   #65
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Well it appears to be feeding an incorrect parameter, whichever it is. Hopefully Sigma will look into this and will be able to quickly isolate the issue. I'm assuming that an update to the firmware can correct it as the optics are not the problem or we would experience the issue whether SR is on or off
01-14-2015, 02:54 AM   #66
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QuoteOriginally posted by sTi Quote
My E-Mail to info@sigma-foto.de (the official contact information on their homepage!) has been returned as "undeliverable" this morning, although it was sent more than a day ago... . I've now tried again from my E-Mail account at work, I hope it gets through this time...
I received a reply from Sigma - they have forwarded the issue to Japan where it will be investigated and will notify me of the results.
01-14-2015, 04:26 AM   #67
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I have been a little disappointed with the wide performance of this otherwise good lens, so read this post with interest. However, I've gone back through my catalogue and picked out a number of shots mainly at slowish shutter speed and 17mm, and all of them have show the SR focal length as 17mm too. This is on a K30 with v1.0 firmware. I haven't been able to find an image that reproduced the problem at all.

01-14-2015, 06:10 AM   #68
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QuoteOriginally posted by MadMathMind Quote
Yes. But if you're saying the lens sends these numbers...
focal length
aperture
...
SR focal length

I don't believe it because why in 1985 or whatever would there be a parameter called SR focal length? And actually, this SR focal length cannot come from the lens. I just checked it on a 200mm lens M series lens. I had input 200mm as the focal length into the camera. It lists the SR focal length as...204mm. Now where did it get that if the lens transmits absolutely no information? There's no option for 204mm. And 200mm is a possibility because I've gotten that with my Sigma 70-200 before.

So, I conclude that the SR focal length parameter is calculated by the camera from the actual focal length and....something else. But what? Clearly, the lens itself doesn't play a role in the process because if it did, we should get the same number for an M lens that the camera was told--or we'd get nothing at all and stabilization wouldn't work for pre-F series lenses. But it does work. So...what on earth does the camera do to get this parameter?
Or, the camera could have a smal "database" of older lens id numbers and from that get the proper SR-focal lenghts.
01-14-2015, 06:49 AM   #69
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QuoteOriginally posted by kilburn Quote
I have been a little disappointed with the wide performance of this otherwise good lens, so read this post with interest. However, I've gone back through my catalogue and picked out a number of shots mainly at slowish shutter speed and 17mm, and all of them have show the SR focal length as 17mm too. This is on a K30 with v1.0 firmware. I haven't been able to find an image that reproduced the problem at all.
Thanks for sharing your findings! Is it possible for you to upload one of your pictures (e.g. on filebin.net) that show the correct SR focal length at 17-21mm? Out of camera JPEG or Raw, if possible. I'd like to take a closer look at the metadata to find out what's going on here.
You do have the "Contemporary" version of the 17-70 and not one of the earlier versions?
01-14-2015, 09:57 AM   #70
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Thank you.

BTW, I forwarded this to Florent of Sigma-rumors.com, and he has posted the issue.

Sigma 17-70mm f/2.8-4 Contemporary: Issue with Pentax's Sensor Stabilization?



QuoteOriginally posted by sTi Quote
I received a reply from Sigma - they have forwarded the issue to Japan where it will be investigated and will notify me of the results.


---------- Post added 01-14-15 at 12:09 PM ----------

Just want to be sure that I understand correctly in that you are not experiencing poorer performance with SR on than off at the wide end for slow shutter speeds. Is that correct?

The rest of us seem to have found that under those conditions image blur occurs with SR on but we are not experiencing it with SR off.

QuoteOriginally posted by kilburn Quote
I have been a little disappointed with the wide performance of this otherwise good lens, so read this post with interest. However, I've gone back through my catalogue and picked out a number of shots mainly at slowish shutter speed and 17mm, and all of them have show the SR focal length as 17mm too. This is on a K30 with v1.0 firmware. I haven't been able to find an image that reproduced the problem at all.
01-21-2015, 12:11 PM   #71
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Sigma 17-70mm Shake Reduction Issue(s)

I want to mention that I really appreciate all the people who took the time to analyze the problem regarding the Sigma 17-70mm f/2.8-4 lens and posting their information and results here. I was planning on purchasing this lens as my first non-Pentax glass in the next six weeks or so, and now I will wait to see if Sigma admits -- and corrects -- the problem. (What should really happen in a fair, honest and reasonable corporate world -- which the informed know no longer exists -- is a recall.)

I have (also) contacted Sigma and directed them to the findings on this forum. Thanks again to those who took all the time and effort to inform others.

Randy

Last edited by Omegaman; 01-21-2015 at 12:27 PM.
01-21-2015, 07:03 PM   #72
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QuoteOriginally posted by Omegaman Quote
I want to mention that I really appreciate all the people who took the time to analyze the problem regarding the Sigma 17-70mm f/2.8-4 lens and posting their information and results here. I was planning on purchasing this lens as my first non-Pentax glass in the next six weeks or so, and now I will wait to see if Sigma admits -- and corrects -- the problem. (What should really happen in a fair, honest and reasonable corporate world -- which the informed know no longer exists -- is a recall.)

I have (also) contacted Sigma and directed them to the findings on this forum. Thanks again to those who took all the time and effort to inform others.

Randy
Well, to be fair, you probably wouldn't have noticed the issue yourself were it not for this thread. Many people here had the lens for months before anyone noticed; there wasn't a single complaint here before this thread. Obviously, there is an issue, but it only comes up in very limited circumstances: the shortest focal lengths with slow shutter speeds. If you're over 1/30 or so, you probably won't see any effect. I can tell that you won't see an issue if you're at "good" shutter speeds, as you can see in this set:

https://www.flickr.com/photos/127442034@N03/sets/72157648971006462/

Here's 1/50 at 19mm: https://www.flickr.com/photos/127442034@N03/15013565523/in/set-72157648971006462

Now, it's understandable that you may not want to purchase a lens that has a known issue. But what are your alternatives? The new 16-85 may be a good one, but it is quite a bit slower throughough its range. The 17-70 Pentax has SDM and all the issues that have plagued it (no definitive proof they are fixed). Think about that a bit. I never noticed an issue because I just avoided the combination that causes it. Well, I guess I did notice the issue but didn't know why. I just knew to avoid it; and 98% of the time, it's not hard to do so. Just something to consider.
01-21-2015, 08:11 PM   #73
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QuoteOriginally posted by Omegaman Quote
I want to mention that I really appreciate all the people who took the time to analyze the problem regarding the Sigma 17-70mm f/2.8-4 lens and posting their information and results here. I was planning on purchasing this lens as my first non-Pentax glass in the next six weeks or so, and now I will wait to see if Sigma admits -- and corrects -- the problem. (What should really happen in a fair, honest and reasonable corporate world -- which the informed know no longer exists -- is a recall.)

I have (also) contacted Sigma and directed them to the findings on this forum. Thanks again to those who took all the time and effort to inform others.

Randy
I had no issues at all with my lens either. When the OP brought up the issue, I had to go back through some of my photos and check the data and saw the large differences in some of my shots. I'm quick to add that the shots I checked are all keepers. I have not had any suspiciously soft shots from my Sigma 17-70C. It's an excellent walk around zoom and I will recommend it to anyone. It also may not be a Sigma problem either. If you follow the accepted practice not hand holding at shutter speeds under 1/30, you will probably never see this issue. The Sigma is a fairly large piece of glass and a bit heavy. You should shoot with that lens at a shutter speed you would use with a mid range telephoto. Crap, the Sigma is bigger than both my 135's! That said, it's still a very odd thing that the SR focal length is on occasion a large difference from the actual focal length, especially since the camera records the proper focal length.
01-21-2015, 11:25 PM   #74
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I have done a bit of testing using my Sigma 17-70 C and found ...

PhotoMe does not say anything about SR Focal Length (the Manufacturer Notes section was meaningless figures).
ExifTool showed both Focal Length and SR Focal Length to be the same (and always correct).

30 of 30 tests at 17mm, with SR off, were sharp (10 each 1/25, 1/50 and 1/500)
29 of 30 tests at 17mm, with SR on, were sharp (10 each 1/25, 1/50 and 1/500)
1 of 30 tests at 17mm, with SR on, was very blurry (at 1/50. Looked like totally missed focus rather than motion blur)
6 of 6 tests at 21mm, with SR off, at 1/25 were all sharp
6 of 6 tests at 21mm, with SR on, at 1/25 were all sharp
SR shutter half press time was always 4 secs or more
All done in Aperture Priority, handheld.

In summary, no issues with my lens. I find it much sharper edge to edge, and wide open, than the old Sigma 17-70 2.8-4 OS that I had a few years ago on a Canon 30D.
01-22-2015, 02:59 AM   #75
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QuoteOriginally posted by Omegaman Quote
I want to mention that I really appreciate all the people who took the time to analyze the problem regarding the Sigma 17-70mm f/2.8-4 lens and posting their information and results here. I was planning on purchasing this lens as my first non-Pentax glass in the next six weeks or so, and now I will wait to see if Sigma admits -- and corrects -- the problem. (What should really happen in a fair, honest and reasonable corporate world -- which the informed know no longer exists -- is a recall.)

I have (also) contacted Sigma and directed them to the findings on this forum. Thanks again to those who took all the time and effort to inform others.

Randy
If you really want to wait for a fix before you buy the lens I think it will take some time. I don't expect a fix soon. Perhaps there won't be any. But like other mentioned it's a good lens anyway. You can also buy new 16-80 pentax.

Last edited by Nitrogliserin; 01-22-2015 at 04:33 AM.
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