Image Stabilization

Back when sensor-based image stabilization (IBIS) first appeared, there was an Internet frenzy over which was better, sensor-based or lens-based shake reduction. Marketing departments at camera/lens companies with vested interests in one answer or the other all fired up their mimeograph machines—uh, I mean marketing teams—and generated a great deal of contrary and confusing "information."

It's way past time to try to present a sane, reasonable explanation of the benefits and drawbacks of each type of image stabilization (IS).

But first, this you need to know: IS does nothing for subject motion. Nothing. The Internet myths you might read such as "four stops of IS equals one stop of aperture or ISO" are something you need to just learn to ignore. If you need aperture (and ISO) to get a usable shutter speed to stop motion, you need aperture (or ISO). Period.

At the other end of the spectrum, at high shutter speeds most IS systems at some point start to take away a bit of edge acuity. Why? It has to do with the frequency of the data sampling and the movement speed of the physical system versus how fast that shutter is moving (mechanical or electronic). For years I've been warning about turning VR off—Nikon's form of lens-based IS—if you're shooting at 1/500 or higher. Certainly above 1/1000. 

So IS is a bit like antilock brakes on your car: when you need it, it's very useful. But you don't always need it.

Okay, so what do IS systems actually do? They do an excellent job of removing camera movement during an exposure. Sometimes wickedly so. I've handheld an Olympus E-M1 Mark II to one second and gotten a very usable shot of static subjects. I've been rocked by boats, planes, trains, and more with wicked vibrations and bounces and gotten excellent shots. I've had stadiums (stadia?) literally bouncing under my feet from fan excitement and still pulled off a sharp shot. 

And, of course, as I get older, it's gotten more and more difficult for me to hand hold slow shutter speeds without some impact. Whereas I used to be very comfortable pushing 1/15 handheld without IS, now I'd say that 1/30 is my limit, and I try to stay above 1/60 if I can. 

Okay, so there are times when IS is useful. Should you get sensor or lens IS? 

Well, both approaches have their pluses and minuses. You should also note that the smart bet these days are on dual systems, which use both approaches. There's a reason for that. 

A lens-based IS system generally is placed near the optical center of the lens (entrance pupil). The reason for this is that you get maximum shift ability with a reasonably small element(s). The smaller the mass, the faster you can move it, and with less force (F = M*A, remember that formula?). Less force also means you don't need strong motors that use a lot of power, so the lens-based systems tend to be kinder on camera batteries.

Another time when lens-based IS is helpful is where the entire system (camera+lens) is rotating up and down or left and right. The longer and heavier the lens, the more likely that the fulcrum point of motion is well forward of the camera body. 

Moreover, with really long focal lengths, you are transcribing a very narrow angle of view overall. A 300mm lens sees about an 8° wide view. At a distance of 50’ (~15m) that field of view is about 6 feet (2m) on the long axis. I've seen people struggling to keep framing (and focus sensor being used) within even a 6" side-to-side position on the subject, which translates to about 500 pixels on a 24mp camera. That's more than you can move the sensor in any IBIS system I know. Yet it seems to be within the range that the lens-based systems can deal with.

The problem with lens-based IS is that it adds cost and complexity to every lens. It also is restrictive in which axes it steadies. Vertical and horizontal shifts are easily handled by lens-based IS, but as you might have seen from marketing materials, we have vertical, horizontal, roll, pitch, and yaw. Lenses can't correct for camera roll, for instance.

The reason why DSLRs don't generally have sensor-based IS is that this wouldn't stabilize the viewfinder prior to shooting. A lens-based IS system does. A stabilized viewfinder is needed to keep autofocus systems aligned to the subject.

Mirrorless cameras, of course, use the image sensor to drive what the viewfinder shows, so having on-sensor IS (often referred to as IBIS) tends to mean that every lens you mount on the camera has some viewfinder stabilization active before you shoot (there may be some exceptions with adapted lenses on some systems).

The issue with IBIS is that it needs information about the lens to work correctly (thus the exception for some adapted lenses), it has a more modest range that it can correct, and it adds heat and mechanical complication at the most expensive part of the camera (image sensor). 

Finally, IBIS tends to not disrupt bokeh in out of focus areas as much as lens-based IS sometimes does. Lens-based IS tends to distort optical paths a bit, while IBIS does not.

Of those, the one that is most important to note is the range limitation. That's why Olympus, Panasonic, and Sony have all gone to hybrid systems with telephoto lenses. In other words, lens-based IS coupled with sensor-based IS. Nikon, too, ends up in this category now with the Z system.

Olympus also still warns about sensor cleaning potentially damaging their IBIS system. (Early Sony systems were also easy to bust, but Sony later changed the design. Nikon locks down the sensor when the camera is off or in cleaning mode, though they also disclaim physical sensor cleaning by the user.)

My only problem with IS is this: some makers seem to be treating it as an "always on" feature. They bury the only way to turn it on or off (or control aspects of the IS performance) deep in some menu you'll not remember the location of. I disagree with that approach. I really want to escalate IS on/off as something I can get to without dropping into menus. As I hinted above, I believe that optimal image capture requires that you use IS conditionally, not all the time. 

Should you pay any attention to the CIPA ratings for IS? 

Probably not. In practice, the CIPA IS ratings are just like the CIPA battery ratings: your mileage will vary. There's really not a dud in the bunch, and any differences in rating don't actually speak to the more practical things you should be aware of.

For example, there is a difference between how well the various IS systems detect whether you're on a tripod or not—yet another reason why I want to take control of the IS setting—or whether you're panning with a subject and the stabilization should default to maximizing a particular correction in that case. That's something I'm struggling to come up with a valid test for, but I do notice differences between the systems. My suggestion: turn IS off if the camera is on a stable support that’s not moving (e.g. tripod on solid ground), and learn whether your camera has a dedicated “panning mode” for IS and use that when panning.

Which brings us to this: 

  • Canon IS— currently relies on lens stabilization (some electronic stabilization for video is done by adjusting the crop, which is quasi IBIS, but that only works for some cameras for some video, and that video is always a crop of the sensor to accommodate the pixel adjustments that are made). It appears that some future cameras may have IBIS.
  • Fujifilm OIS — some bodies have IBIS (e.g. X-H1), some don't (e.g. X-T3).
  • Hasselblad — no stabilization.
  • Leica — no stabilization.
  • Nikon VR — IBIS for the Z6/Z7, plus many adapted lenses have lens IS and the two work in conjunction. For the Z50, the DX lenses have lens-based IS.
  • Olympus IS — originally only IBIS, but now making telephoto lenses with lens IS that works in conjunction with IBIS.
  • Panasonic OIS — originally only lens IS, but now making IBIS on most models (GH5s is an exception).
  • Sony OSS — IBIS plus lens stabilization for telephoto lenses that works in conjunction.

All else equal, I'd rather have IBIS (sensor based) than not, but I want that to work with lens IS for telephoto lenses. Nikon, Olympus, Panasonic, and Sony are getting this right, in my opinion. But I also shoot a lot without IS turned on, particularly when I ‘m shooting at high shutter speeds (>1/1000 second). I prefer that IS be settable by an external camera control, not buried in the menus (Nikon gets this right, at least with lenses that have VR switches).

Final note: Beware using the CIPA numbers about how many stops the stabilization accomplishes to choose a system. The CIPA tests are three-axis only and don't exactly mimic the situations you'd be using IS for. I've found that all the IS systems work well, but there's variability above and beyond what the CIPA numbers suggest.

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