There are some things every person takes for granted.  Eyesight, for instance, is an easy enough ability which is low priority, till you lose it, you start having problems with your eyes, or you start having headaches.  For an SLR camera (film or digital), most everyone will say that the most important part is the lens.  And most everyone will also say that they bought the lens without any idea how well it works besides the zoom factor or the f-number.

Most lens buyers would not take the time to shoot a picture before buying a camera.  In fact, practically nobody notices that a kit lens may not give the sharp pictures.  And to think that there are some lenses out there which are more expensive than the camera body.

The most common problems for a lens are barreling and pin-cushioning.  To understand this better, understand the main feature of a fish-eye lens: the edges are curved and the middle is enlarged.  This is barreling taken to it’s logical end.  Named after the way a barrel has curved sides, barreling is a side-effect of wide-angle lenses.  The wider the angle (like that of a fish-eye lens) the more pronounced the barreling.  For regular wide-angle (28mm for a 35mm camera) this should be nonexistent or insignificant.  But with a shorter focal length, barreling would be inevitable, and would be only a question of how much does it affect the picture.

On the other end of the spectrum, pin-cushioning occurs when the straight lines on the edges of a picture curve inwards.  This effect is more common with long lenses.  Barreling and pincushioning are both sides of the same coin, and it’s an indicator of how good the zoom lens is.

Barreling and pincushioning are less common in primary lenses, as these fixed-length lens were designed not to have these effects.  There are 18mm wide-angle lenses with minimal barreling. Minimal meaning that it’s noticeable but kept low, and therefore acceptable.  And for fixed length long telephoto lenses, pincushioning is almost nonexistent.  At least these problems do not appear or are kept to a minimum.  It would be a shame to have a 400mm reflector lens with noticeable pincushioning.

There is only one way to check if the lens has this problem and that’s to take a picture, preferably of straight horizontal and vertical lines.  If it’s not possible to take a picture and develop it, you would have to content yourself in looking through the viewfinder.

For a point-and-shoot and bridge cameras with large magnification (5x and up), expect barreling and pincushioning to appear in shots with the wide-angle and maximum telephoto shots.  There’s nothing anyone can do about this, as the lens are not interchangeable.

However, there is a workaround and it depends on studying the camera.  Take test pictures vertical lines.  The multiple shots should be from the widest angle to the highest zoom.  Study the resulting pictures and take note at what lens lengths the barreling and pincushioning becomes pronounced.  And if you don’t want these effects to appear (and ruin) your pictures, then don’t use these arbitrary lens limits.