Im pretty sure you all must of heard of the word "prime" mentioned in photography from time to time and wondered what we might be talking about. So, for those of you who are not quite sure about the definitive meaning of the word "prime", I thought I might enlighten you all. A prime lens is one that has just one focal length only in contrast to say a zoom lens which will cover wider lengths. The glass used in the manufacture of these lens is of a much higher quality than lets say your standard consumer grade lens. Other clear advantages are that prime lens offer higher speed. They are sometimes referred to as "a fast lens" which means the larger the maximum aperture is, ie the f stop, the faster the lens is. Another way of describing it is to say they let much more light in. I hope all of this makes sense. What I thought I would do is give you two example's of the same image so you can make that comparison. One taken with a standard 20mm lens and the other with a prime lens. Both with the same settings, same light and the same conditions. Example one: Standard 20mm Example two: Prime 20mm Now, if you look closely at both of the images you will see that the image taken on the prime lens has a great sharpness and depth to. Thats the difference.