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05-03-2011, 09:38 AM   #1
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Question on Sigma OS lenses

One of the reviews for the Sigma 17-70 OS HSM lens states that Sigma's OS is always on even when it is switched off.

If true, it makes no sense to have an on/off switch.

Can anyone confirm or refute this assertion?

Thanks.

05-03-2011, 10:56 AM   #2
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I have two Sigma OS lenses and I'm pretty sure that when it's switched off it's actually off.
05-03-2011, 12:00 PM   #3
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Reviewer screwed up.
05-03-2011, 12:11 PM   #4
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Maybe, if the review was of a pentax one, he meant that OS and in-body stabilization did a similar job and that turning it on didn't make any difference...(or he screwed up as said before).

05-03-2011, 03:23 PM   #5
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Thanks everyone. It made no sense to me that OS would stay on regardless of the switch setting. I keep the switch off and keep SR active, just wanted to be sure that there was no conflict taking place between the two methods.
05-04-2011, 01:13 AM   #6
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I guess what the review tried to say is that the electro magnets have to keep the floating element in place even if you disable OS - the same way as the electromagnets have the keep the floating sensor in place even if you disable SR. So if disable OS then it won't compensate for shake, but it still consumes power since it still has to keep the floating lens element in a fixed position. When you power off the cam (or you don't use the lens for some time) you can feel and hear the lens "dropping" the floating element - if you power on the cam or use the lens then the electromagnets engage again.
05-04-2011, 01:33 AM   #7
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It is off when you turn it off, at least my copies do.

But I think the lens still consume battery power as simico stated.
05-04-2011, 02:22 AM   #8
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It sounds really weird that the lens needs to be powered even with OS turned off, as it would prevent you from using it on any system without SDM contacts, even by using it manually.
Has anyone tested such a lens on a non SDM body, or with a non SDM converter ?

05-04-2011, 02:36 AM   #9
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I can try later with power off in the view finder. I guess it is possible to shoot purely manual, but the lens element do shake a bit. My copy does.
05-05-2011, 12:32 AM   #10
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QuoteOriginally posted by ZEPsikopat Quote
as it would prevent you from using it on any system without SDM contacts
And why would anyone buy a HSM OS lens if he has an ancient camera without SDM contacts? You think Sigma (or even Pentax with its KAF3 lenses) cares about that minority?
05-05-2011, 04:27 AM   #11
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QuoteOriginally posted by simico Quote
And why would anyone buy a HSM OS lens if he has an ancient camera without SDM contacts? You think Sigma (or even Pentax with its KAF3 lenses) cares about that minority?
Simply because you would be screwed with one of their TC ?

Pentax KAF3 lenses can be used on non-sdm bodies, althought they become manual focus.

Sigma states on their website that the HSM lenses become manual when paired with one of their TC, but the only thing they say about OS is :
QuoteQuote:
*For Pentax and Sony mounts, it is not possible to use the AF and the built-in OS function of this lens when attaching it to film SLR cameras as well as Pentax *ist series and K100D.
So one would think you can use an OS lens in manual mode without any issue, and my concern was to know if it was the case
06-20-2011, 06:50 AM   #12
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Sigma OS on Pentax

Sorry for the confusion guys! I am probably the reviewer that everyone mentioned at the beginning of this thread. I re-read what I wrote and its misleading =( Let me try to be clear about what I said in my review... Even though you manually turn of Sigma's optical stabilization via the switch on the lens, the floating lens elements responsible for OS are still powered on, as in still gyrating, but do not engage when you half press the shutter. I came to this conclusion because whenever my k-x goes into power saving mode or I turn it off I can actually feel and hear something inside the lens power down. For anyone with a Sigma OS lens, listen to your lens up close before you turn on your camera, make sure beforehand both SR and OS are switched off, and you will still hear the floating lens elements spin up, thus consuming power. Turning the switch off obviously turns off (disengage is more appropriate term) lens optical stabilization but not power consumption.

Last edited by wutsurstyle; 06-20-2011 at 07:03 AM.
06-21-2011, 06:18 AM   #13
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I can verify the last statement. In my copy of the Sigma 17-70 OS HSM I can distincly hear a sort of a thud sound when the camera goes into a power saving mode.
06-21-2011, 07:07 AM   #14
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QuoteOriginally posted by wutsurstyle Quote
Sorry for the confusion guys! I am probably the reviewer that everyone mentioned at the beginning of this thread. I re-read what I wrote and its misleading =( Let me try to be clear about what I said in my review... Even though you manually turn of Sigma's optical stabilization via the switch on the lens, the floating lens elements responsible for OS are still powered on, as in still gyrating, but do not engage when you half press the shutter. I came to this conclusion because whenever my k-x goes into power saving mode or I turn it off I can actually feel and hear something inside the lens power down. For anyone with a Sigma OS lens, listen to your lens up close before you turn on your camera, make sure beforehand both SR and OS are switched off, and you will still hear the floating lens elements spin up, thus consuming power. Turning the switch off obviously turns off (disengage is more appropriate term) lens optical stabilization but not power consumption.
You have it absolutely correct. I have the Sigma 17-70 OS and previously owned the 70-300 OS too. The 70-300 made a very obvious 'whirring' all the time the camera was powered on, even when OS was switched off. Believing this might have indicated a fault I queried it with the importer and was given more or less the explanation provided above. I believe the same is true of other brand's OS systems too.

Oh, and FWIW in my opinion the Sigma lens OS system is probably worth an extra stop compared to the in camera stabilization from my K20D. Probably a comment to be regarded as heresy around here. But there it is - I said it!
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