Exposure and focus are just the beginning. If you don’t use your lens properly, your photo won’t turn out as planned. Here are three common optical problems and how you can overcome them.
1) Barrel distortion: If your photos have bowed lines, your lens has poor distortion control. So reframe your shot to eliminate the bends. Compose ultrawide pictures with straight lines situated away from the edges of the frame, and move people toward the center to avoid unflattering distortion of faces and bodies.
2) Glare and vignetting: Not using a lenshood in sunny scenes can cause photo-killing glare. Similarly, lenses whose front element extends beyond the barrel (some ultrawides and telephotos) are prone to flare. But on some lenses at wide settings, lenshoods may cause vignetting, so look before you shoot. Also, make sure your lens doesn’t block your on-camera flash.
3) Color fringing: Purple, red, or cyan edges around objects are only rarely visible, even when a photo is enlarged, but they can still compromise sharpness and contrast. This happens most often with distant or backlit subjects shot with a telephoto. Look for a lens with low-dispersion glass elements if you’re shopping for a new tele. Otherwise, try shooting at a smaller aperture, or fix the image later in postproduction.