Image stabilization - it's a wonderful thing.
Mind you, it's not going to cure illness, curb bad habits or make you any more attractive, but it sure will make your photos look nice.
Like all good things, image stabilization does come with some limitations, and that's what I'm going to explain here.
Before I can talk about why image stabilization is so useful, I have to address the problem that it's trying to solve: motion blur.
There are two ways motion blur can become apparent in your photos:
In both cases, blur is the result of a shutter speed that is too slow to prevent motion blur. Any time you use fast shutter speeds - anything between 1/125th and 1/4000th of a second, you're not going to see very much motion blur in your pictures: everything will be nice and sharp.
But once you drop down to 1/60th of a second or slower, you're right on the edge where motion blur will become apparent. Depending on your subject, you may see blur in some photos and not in others.
Subject Motion Blur
Subject motion blur occurs when your shutter speed isn't fast enough to freeze your subject. The shutter speed you need to use to prevent motion blur depends entirely on HOW FAST your subject is moving.
For example, a shutter speed of 1/125th of a second might be fine to freeze a small child on a trike, but it's not nearly fast enough to freeze an adult tearing past on a motorcyle. For this, you'd need to increase shutter speed between 1/500 and 1/1000th of a second for a clear shot.
This assumes the motorcycle is in motion. If you're just taking a portrait of someone sitting on a non-moving cycle, then those fast shutter speeds really aren't necessary.
The most obvious way to spot subject blur vs. camera blur is this: with subject blur, the background will be clear and ONLY the subject will be blurry.
Camera Motion Blur
With subject blur out of the way, let's talk about camera blur. You can instantly tell when you're looking at camera blur because your entire photo (background and subject) won't be sharp.
Camera blur occurs when you use very slow shutter speeds and take pictures holding the camera in your hands. What's a slow shutter speed? While it can vary, a general rule of thumb is that anything slower than 1/30th of a second is pushing the blur boundary.
The level of camera blur depends on the amount the camera is moving around. If you're taking pictures standing on the ground and are just holding the camera in your hands, then you can use relatively slow shutter speeds (between 1/15 and 1/30) without having to worry about blur.
However, if you're the passenger in a car driving down an unpaved dirt road, then camera blur might become visible between 1/60 and 1/125. The greater the camera motion, the faster the shutter speed needs to be to eliminate blur.
Keeping It Steady
Image stabilization systems are only useful for combatting camera motion blur, despite what the marketing materials would have you believe.
Since the stabilization system cannot force your subject to stay still, subject motion blur can still be a problem even if you're using the most sophisticated stabilization in the world.
Most stabilization systems work by keeping the imaging sensor steady even when the camera is moving all over the place. As far as the sensor is concerned, the camera is perfectly stable.
A stabilization system lets you use very slow shutter speeds when holding the camera in your hands, a great tool for landscape photographers who don't want to always carry around a heavy tripod.
It's also a great tool for people who like to photograph in dim light - just remember, if you're taking photos of moving subjects they will have to stay still to prevent subject blur.
In Body vs. In Lens
There are two places where an image stabilization system can be placed: in the camera's lens or in the camera's body.
The advantage in-body stabilization is that it works with ANY lens that you attach to the camera. If you're using a camera without body stabilization and attach a normal lens to it then the image stabilization is lost.
If you only want to take pictures of active subjects then stabilization is less important. But if your passion is wandering around cities at night and snapping photos, then having a lot of flexibility in your stabilization system will be key.
Motion blur occurs when the camera's shutter speed is too slow to freeze either subject motion or camera motion.
Image stabilization systems only help to counteract camera motion - they don't help at all to make moving subjects look sharp.
Stabilization can either be included in the camera body - in which case it works with every compatible lens - or it can only be in special stabilized lenses.
The necessity of a stabilization system depends entirely on what you like to photograph: landscape, nature and night photographers will use it often while sports photographers won't need it at all.
Mirrorless Camera Terms