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Optical image stabilization has been around for generations of cameras. It’s found in more and more cameras & lenses today as the technology becomes smaller and cheaper. But this has left a lot of people wondering what’s in the specs. What does “stops of stabilization” mean for lens and in-body stabilization?
What are “stops”?
I think we all have a good idea of what “stabilization” is. Most of us know that this will help us get sharper photos by reducing “shake” or “vibration” while the shutter is open. If the camera or lens is shaking as the shutter is open, our photo won’t be as sharp.
What confuses some people is the definition of a stop, and how this relates to stops of stabilization.
A stop is a measurement of exposure, or brightness. If we increase the exposure by one stop, the photo will be twice as bright as before. If we decrease the exposure by two stops, the photo will be 1/4 as bright as before (half of one-half). And so on.
One way we do this in photography is by adjusting the shutter speed.
Let’s say we create an exposure at ISO 200, f/8, and a shutter speed of 1/125th of a second. One way to alter the brightness is to change the shutter speed.
- Changing the shutter speed to 1/60th sec will make the photo twice as bright (the shutter is open twice as long).
- Changing the shutter speed to 1/500th sec will make the photo a quarter as bright (the shutter is open for a quarter the amount of time).
The relationship between stops and shutter speed is fairly straightforward. Doubling or halving the shutter speed will also double or halve the exposure (brightness), respectively.
You can read this article for a deeper discussion on “stops” and using them in exposure.
How do stops relate to image stabilization?
Ok so how does this all relate to stops of stabilization?
Well, as we mentioned, we love stabilized lenses and cameras because we can handhold the camera at slower shutter speeds. We can still create sharp photos at slower (longer) shutter speeds without using a bulky tripod.
The inverse focal length rule
There’s an easy little rule to follow to get a general sense of how slow of a shutter speed you can use and still hope for a sharp photo. Just invert your focal length (its full-frame equivalence focal length).
If you’re using a 50mm lens, you can usually slow down your shutter speed to 1/50th second without any noticeable blur. Anything slower, like 1/25th second, and you risk camera shake while the shutter is still open.
Zooming in with a 200mm lens, any camera shake is magnified, so you can only slow down to 1/200th second. And using a wide 15mm lens, you can usually go as slow as 1/15th second and still get a sharp photo.
There are, of course, several other factors that go into this “rule.” But this is one of those easy little things you can hang your hat on in a pinch. You won’t be able to slow down your shutter speed as much if you’ve got the mid-morning coffee jitters like me. Or you might be able to go slower than these rules if you have rock-steady posture.
Examples of stops of stabilization
This is where stops of stabilization now comes in.
We know what a stop is.
And we also know how slow of a shutter speed we can generally use to make sharp photos by hand.
If a lens claims to have “five stops of stabilization,” then that means you can make your shutter speed five stops slower and still get a sharp image, compared to the same conditions without stabilization.
- You’re using a 50mm lens and can only slow down to 1/50th second before you start noticing blur in your photos.
- Add five stops of image stabilization to that lens and now you can hold it by hand down to 1/2 second before you start noticing blur in your photos. That’s a long shutter speed!
Both cameras and lenses equipped with this technology will usually say how many stops of stabilization it has in the technical specifications or marketing materials.
It’s a great feature to have if you’re making photos in low light and want to keep the ISO low, using a longer shutter speed. Here are some more examples:
- A camera with IBIS (in-body image stabilization) advertises four stops of stabilization. With a 400mm lens, you can hold that by hand down to 1/25th second and still hope for a sharp image (1/400 – 1/200 – 1/100 – 1/50 – 1/25).
- Your zoom lens advertises six stops of stabilization. Zooming it in to 135mm, you can expect a sharp image at shutter speeds as slow as 1/2 second (1/135 – 1/70 – 1/35 – 1/15 – 1/8 – 1/4 – 1/2). You can see I’m rounding there to maintain standard shutter speeds, but that’s the gist of it.
Don’t base your lens or camera purchasing decisions solely on how many stops of stabilization they might have. Like if the subjects in front of your camera are always moving, then this is all a moot point because you’ll need to maintain faster shutter speeds to ensure that their movement is frozen (not yours).
But if you are purchasing a camera or lens with this technology, then I hope you now have an idea of what it means with they say stops of stabilization.