Despite being a beautiful image, a lenshood may have helped to reduce the flare in Flickr-user Mustafa Sayed's photo.
9. No Lens is Perfect No lens is perfect, and some lenses are more imperfect than others. Among common imperfections, perhaps linear distortion is the most noticeable and annoying. This is the tendency of a lens to bow straight lines outward (barrel distortion) or inward (pincushion distortion). These days you can minimize distortion in your photos using software (see Software Workshop on page 46 to learn how).
Because lenses bend light, they can also act as prisms and break light up into the component colors of the spectrum. Known as chromatic aberration, this appears as color fringing and softness, most noticeably at the edges of the frame. You can almost always reduce it by stopping down to a smaller aperture.
Light falloff (vignetting) is the tendency of the lens to produce an image that’s darker at the edges, especially the corners. You can lessen it by stopping down or fix it later in software.
Flare shows up as veiling fog and spectral blobs when you aim the camera directly at a bright light. Lenshoods can reduce this, and stopping down to a smaller aperture sometimes helps.
TIP: Distortion is most severe at the very edges of the frame. With a distortion-prone lens, keep straight lines away from the edges by stepping back or altering the composition.