Lens Problem No. 2: Vignetting
This is characterised by a darkening of the corners of the frame, and is caused by the lens actually capturing its own sides. It’s particularly noticeable when you’re shooting a clear sky.
The problem is usually associated with wide-angle lenses at wide apertures, although it only becomes a concern when you’re shooting on a full-frame camera (do you really need a full frame DSLR?), which makes use of the full diameter of the lens.
Vignetting can be a positive creative tool as well, helping to draw attention to the centre of the frame.
If you notice dark corners, try zooming in a touch, or set a narrow aperture.
Alternatively, Photoshop’s Lens Correction tools (Filter>Distort>LensCorrection) do an excellent job of eliminating (or enhancing) vignetting.
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