I own a Canon 7D and a EF-S 15-85 IS lens and I keep the image stabilization turned on all the time.
Recently, an experienced photographer told me that this is a huge mistake because it reduces image quality overall.
Except the battery draining, is there any evidence that using IS the image quality will be reduced?
Thank you :)
Image Quality will not be affected at all. The light still passes through the same piece of glass whether it is on or off.
You might get a feedback loop if you have the IS on whilst tripod mounted (unless the lens can detect it is tripod mounted) where the vibrations of the glass being moved by the IS system cause further vibrations but this causes a motion blur type effect and still wouldn't affect the image quality, rather the quality of the image...
Using IS in an environment where lots of vibrations are present (on an aircraft / car on a bumpy track) it can have an effect also.
I don't know how it works with this lens, but I've seen charts for Pentax's in-body stabilization system where the data shows that contrary to conventional wisdom I.S. gives a (decreasing but still there) benefit up until rather high shutter speeds, at which point it doesn't matter (and doesn't make things worse).
If you have the camera on a very steady tripod, though, off is probably better. On a lightweight, wobbly tripod, it may be different.
It's also important to keep in mind that the stabilization takes time to engage and "settle" — typically half a second or so after you half-press the shutter button. If you have it on, make sure to allow that time.
Update: I don't think these are the charts I remember, but they show the same thing and are quite well done: How can I determine the minimum shutter speed to avoid blur from camera shake?.
I heard about IS affecting the Bokeh. The reasoning seems sound to me: the optical path (optical IS) is varied or the lens plane is moved (sensor IS) leading to a different distribution of the typical "lens sharpness" compared to a non-stabilized lens. This will perhaps be more visible because you expect a uniform distribution of bokeh on a far-away background and at the edges.
It would certainly be worth testing this in a controlled setup. No, I'm not going to do anything about it ;)
What kind of images do you shoot? If you always take pictures in bright light at 1/250 of a second or faster and you have very steady hands, then IS may not be helping you. On the other hand, if you're usually taking pictures in low light (say 1/25 or 1/50 of a second or even longer) or you don't have a good stance, then IS is probably making your pictures a lot better. If you are moving back and forth a lot between those two scenarios (I know I do), then just continue to leave IS on because, at least in my experience, the benefit to the low-light pictures is far greater than any potential harm to the brightly-lit pictures.
Of course, since you're getting conflicting advice here, I'd recommend running your own experiment. On the next sunny day, go out and take some photos with the same settings (aperture, ISO, etc.; you'll probably get a more accurate test if you use your normal settings to figure out the exposure and then take the test pictures in manual mode, so exposure settings don't change between pictures) you normally use, both with and without IS, and compare the results (and please report back here when you're done!).
Here is an interesting article about Nikon VR, but I think a lot of applies to image stabilization in general.
The author touches on the issues a little bit in the beginning, but his main rule is to never turn on VR when it's not needed.
As someone who uses the IS capability of the EF 100-400mm L series lens a lot, I can say that it is something you need to choose to use. IS is a tool, and it is designed to solve a specific problem. Its not the ubiquitous hammer that can apparently solve every problem known to man, so you need to be explicit about the cases where you use it.
IS is intended to improve the performance of a lens when hand held, in situations where hand-holding is either not possible, or difficult. If you have enough light to follow the
Focal Length Reciprocal rule, which states that a shutter speed of 1/FocalLength at a minimum (without IS) should be used to capture a sharp photo, then turn off IS. If you do not have enough light to capture a sharp photo at a proper exposure with the reciprocal rule, then you should enable IS before you increase the ISO. The IS system of the 18-55 might get you 1-2 stops of additional hand-holdability, while better IS (such as that on the 100-400mm) may get you up to 3-4 stops additional hand-holdability. That means you could reduce the shutter speed up to two stops lower than the reciprocal rule would dictate, and get a clear shot. At 55mm, that would mean a shutter speed of 1/15s (+2s tops) should be sufficient. At 400mm, that would mean a shutter speed of 1/100s (+3 stops).
If you are unable to get a shot by enabling IS, then its finally time to crank up your ISO. As a general rule, I try to keep my ISO as low as possible. In the case of shooting wildlife and birds, I tend to set my ISO to Auto, and unless I'm photographing in bright daylight, I turn IS on in mode 1 (stabilization in both horiz and vert planes.)
In most circumstances it's safe to leave it on all the time, particularly if it's implemented in a smart kind of way.
For image stabilisation to work it needs to detect, at high speed, fine rotational movements. However no such detection is ever 100% accurate - there's always an error margin which translates to very fine, low level movements. This never matters in normal situations where you'd use it, because in reality holding the camera by hand at 1/250th or slower will always generate far, far more movement than any inaccuracy of the image stabilisation system. So it's a net gain.
When the camera is locked down completely with a tripod, however, then there should be no movement of the camera. So not only is IS not needed, but you wouldn't want the inaccuracy of its rotational detection system to generate tiny movements at all. Even though any motion will be less than hand-holding at a normal shutter speed, if you had the ability to have less chance of blur, you'd take it wouldn't you?
Some cameras are smart enough to detect they're likely on a tripod and won't move the IS system, just like some cameras will automatically turn off IS for shutter speeds of 1/500 and faster. But it's kind of hard to find out this information about any particular lens or body.
If you search around here and elsewhere you'll find lots of arguments for and against when one should/shouldn't use IS/VR/SR. The remarkable thing about so many words exercised is that it's so easy to test and decide for yourself, your own use, and your own standards. Take some pictures in the same way with and without it. Look at them closely. Can you tell the difference for better or worse? Do you care? There's your answer.
For example, I've tested a couple of my (Nikon) lenses on a tripod with VR operating, and not. Couldn't tell any difference at 100%. That's good enough for me. I still turn it off because the delay it causes can be a little annoying, but if I forget, no worries.
And another thing, seeing as I'm here. That 1/focal length rule? Completely bogus. To think that so many variables involved in hand-holding steadiness could be reduced to such a trivial formula? It really doesn't withstand any scrutiny. Curiously, it's another myth that digital photography makes very easy to test for oneself, yet so few seem to. It's funny how the quoted rule didn't change when so many folks started using less than 'full frame' sensors, though.
The only argument I've heard is about battery life -- if you don't need it, turn it off to save the battery.
Image quality can be adversely affected if the camera is on a tripod, or if the focal length is out of bounds of what the IS system "expects." For example, some cameras and/or lenses recommend disabling IS for macro photography. But in the tests I've tried, it hasn't made a significant difference and it's usually hard to see any degradation.
For me the big problem with Image Stabilization is that it takes a while to "wake up", if you just want to take a very quick picture of a fast moving object, chances are the first one will be blurred by the IS system, even when using a high shutter speed (e.g. 1/250 at 30mm).
At least that's how my Sigma 17-70 OS seems to behave.
I guess it's still better to leave it on all the time when "walking around". This way you don't have to remember to put it back on when lighting conditions change to low light.
I found myself a few times caught with IS off when I really needed it. It simply isn't a habit of mine to check this switch on a lens.
All in all I found myself to have many more "rescued" photographs due to IS being on, than ruined due to it misbehaving.
I have a Sigma 150mm to 600mm Sport lens on a Canon T6i. In low light the OS (optic stabilization) works wonders. In good light the OS absolutely ruins pictures. I have forgotten to turn the OS off several times and wasted the whole days worth of photos. I am not sure why the answers are so varied on here. Maybe Sigma's version of Image Stabilization is flawed? Maybe people don't know what a sharp photo looks like? I can't say. I leave OS off all the time so I don't forget to shut it off.