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Hey, all -- I'm not sure if my Sigma lens is acting normally or not. Maybe someone here has a similar experience.
I own a Sigma 70-300mm DG lens with optical stablization (or stabilisation, if you prefer), which I'm very happy with. But it has one bit of odd behavior: When the optical stabilization is on, the autofocus starts with a small jolt -- that is, the lens clicks for a second, the frame shifts slightly, and then it focuses smoothly and normally.
Without the OS on, autofocusing is smooth. There isn't that initial jolt/bump/click thing.
The results look fine, although I haven't tested recently whether the stabilization makes a difference.
Has anyone else notice this slight initial jolt/click normal with the optical stabilization?
Thanks for any feedback!
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My Canon IS lenses do that. When you half-press the shutter button, it takes about half a second for the camera sofware to work out the vibration pattern and then the IS mechanism kicks in and that is the 'jolt' you see. If you look closely, you will see before the holt the image moves about slightly with camera shake, after the jolt it stays steady.
This is why some people who shoot birds/action turn the IS off - this lag can cause otherwise good shots to be blurred because the IS has not yet settled down.
Ahhhhhhh. Thank you. I feel much better. It's my first (and only) lens with an optical stabilizer, and I was worried I'd be without it while it was serviced. [whew]
My new 120-300 F2.8 OS does exactly the same.
I own Sigma 18-125mm lens. And I remember reading in the manual that OIS needs about 1c to "catch up", after which it holds the image. While I did not find it very inconvenient in practice, my plasticky 18-55 Canon lens does not show this type of behaviour, and focuses pin-sharp. Opposite to that, Sigma is great with my old EOS10D, but presents with front-focus nightmare on EOS550D. All Canon lenses I have focus perfectly fine on both. The pay for the cheap brand I suppose. Better cheap lens from the good brand than the opposite.
I've been shooting with Sigma's OS stabilized lenses for some time and own over 20+ Sigma lenses. I have yet to experience a back or front focusing issue. I know this is an issue, but am not sure it is a Sigma lens issue but the Camera manufacturer's variation in its quality control on its lower models. I've never experienced this problem with my high end pro Canons. That being said, you have the option of sending the lens and camera into Sigma UK and have them calibrate the lens to your specific camera. I'm in the U.S.A. and Sigma USA does this at no charge. Can't speak for Sigma UK. I shoot with top of the line Canon lenses with OS and these lenses do the same thing that the Sigma lenses do in terms of stabilization. I have some cheaper kit lenses from Canon and these lenses' OS behave exactly the same as the more expensive ones. Most of the higher end cameras have the ability to adjust focus + or - to address focusing accuracy. In addition, Sigma's newest lens lines have the ability to hook the lens up to a USB port and to adjust that lens to your specific camera which I believe is the best solution. But in response to the OP's post--the description of your experience is exactly the experience I have with my Sigma lenses with OS.
I am pleased to know that you are one happy Sigma user. Though focusing problems with Sigma are not uncommon. My practical experience and simple Google search of the net look quite convincing to me. Would not say the lens is bad, but it just does not work on every DSLR body - and better be tested with the camera before buying . Maybe, an advanced entry level camera is not good for the lens - or lens for the camera? Their cost is pretty much equal. As for calibrating the camera or the lens, or both of them together - thought about it, but found it impractical - as the problem specifically manifests itself with this particular camera and this particular lens. While having more than one lens and more than one DSLR body I believe mutual fitting of one lens to one body will do more damage than good. Such a dilemma... But thanks for your experience and the advice - single body/single lens owners may take it (if we find such a photographer) For the guys who have a situation similar to mine I've got a tip - use live view option, this one (although slow) does give results more precise (and controllable) than conventional way of focusing. Also is great for manually focused lenses ( no AF) - especially with centre spot magnified. Cheap lens is not for sports of any fast action anyway.
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