Difference Between USM and IS

USM vs IS

The terms USM and IS are commonly used in camera lenses. Although they are vastly different from each other, there is one thing that is common to them; they both jack up the price of the lenses that have them. Before tackling on the differences between these two, keep in mind that they are completely different features and are not competing with each other. You can have either, neither, or both with your lens. USM works on the autofocus mechanism of the lens while the IS compensates for the motion of the camera by moving the lens element inside.

USM, which stands for Ultrasonic Motor, is an alternative way of moving the lens element inside in order to bring the subject into focus. USM has several advantages compared to ordinary motors, including much faster autofocus and reduced noise in the mechanism. Its autofocus speed lends itself nicely to shooting moving targets where catching specific moments is key.

On the other hand, IS stands for Image Stabilization. Although there are different implementations of this feature, its aim is to eliminate or at least reduce the amount of blurring that occurs due to the motion of the camera, or the hand that is holding it. No matter how still you try to keep your hands, there would always be some amount of shake that causes slight blurring. This becomes even more acute the farther you zoom out. IS combats this by constantly moving the lens element inside to compensate for the motion and reduce the blurring that it causes.

As you may have already deduced, IS can greatly enhance the photo you shoot when the camera is on your hand. USM does not directly affect the image quality but is great to have if you are constantly shooting moving subjects. The silence of USM lenses is also very desirable when shooting animals in the wild so that they do not get spooked.

The use of USM was pioneered by Canon and only their lenses carry the USM label. Although the same technology is employed by other camera manufacturers, it is known under different acronyms. IS is a general term and most camera manufacturers use it to indicate that their cameras have image stabilization.

Summary:
1. USM is part of the autofocus mechanism while IS minimizes camera shake
2. USM does not affect the quality of the photo taken while IS does
3. USM affects the shooting speed and noise of the lens while IS does not
4. The term USM is exclusively used by Canon while IS is used by all camera manufacturers

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