Some lenses produce pictures that appear darker around the edges of the frame than in the center, even when the lighting is consistent throughout. This phenomenon goes by several names, but the two heard most often are vignetting and light fall-off. How much vignetting occurs with your Canon EOS 60D depends on the lens, your aperture setting, and the lens focal length.
The EOS 60D offers the Peripheral Illumination Correction feature, designed to compensate for vignetting by adjusting the light around the edges of the frame. In the top image, light fall-off is noticeable at the corners. The bottom image shows the same scene with Peripheral Illumination Correction enabled. The Peripheral Illumination Correction setting is available from the camera, applied to JPEGs, but you can also apply (or unapply) it to raw photos in Digital Photo Professional.
This “before” example hardly exhibits serious vignetting; it’s likely that most people wouldn’t even notice if it weren’t shown next to the “after” example. Unless you turn off this option, you’re not likely to notice significant vignetting with the 18-135mm kit lens bundled with the camera. But if your lens suffers from stronger vignetting, it’s worth increasing the Peripheral Illumination Correction filter.
Peripheral Illumination Correction is available in all your camera’s exposure modes, including all the fully automatic modes. But, a few factoids need spelling out:
The correction is available only for photos captured in the JPEG file format.
For the camera to apply the proper correction, data about the specific lens has to be included in the camera’s firmware (the internal software that runs the digital part of the show).
If your lens isn’t supported, you may be able to add its information to the camera; Canon calls this step registering your lens. You do this by cabling the camera to your computer and then using some tools included with the free EOS Utility software, also provided with your camera. (You use this same software when you choose to download photos by cabling the camera to the computer instead of using a memory-card reader.)
If you’re using a third-party (non-Canon) lens, Canon recommends that you not enable Peripheral Illumination Correction even if the camera reports that correction data is available. You can still apply the correction in Digital Photo Professional when you shoot in the Raw format, though. To turn off the feature, select the Disable setting.
In some circumstances, you may see increased noise at the corners of the photo because of the correction. The exposure adjustment can make noise more apparent. Also, at high ISO settings, the camera applies the filter at a lesser strength, presumably to avoid adding even more noise to the picture.