At the bottom of the consumer line are the cheapies - ultra-low cost, low-quality, slow lenses with plastic mounts and no distance scales. Most of the kit lenses - 28-80 and 28-90 lenses with typical aperture ranges of 4.5 to 5.6 - fit into this category. These lenses are built to be sold as inexpensively as possible and don’t have very good optical quality. The only exception to this basic rule is the 50mm 1.8 II - plastic lens mount - which has excellent optical quality despite its cheap build quality, because it isn’t a zoom lens like all the others. The cheapies are easily recognizable by their all-plastic construction and straight, parallel-sided lens barrels. Most of the new cheapies have a silver (chrome) ring around the end for looks.

The Canon EF Lenses  includes a ring-type ultrasonic motor (USM), which allows full-time manual focus, even when the camera/lens are set to autofocus. Autofocus is slower and more cumbersome than with a non-macro lens, due to the large range of distances available. The lens has an internal/rear focusing system, so the length of the lens and therefore distance of the front element from the subject does not change as the focus ring is moved. The lens is a flat-field design, optimized for edge-to-edge sharpness of flat subjects.

This lens categorization sometimes gets very confusing. For example, Canon release newer versions of lenses all the time, numbering them with Roman numerals. Sometimes the new lens is an improvement. Other times it’s not.

For example, the EF 28-80 3.5-5.6 USM isn’t a bad lens. It has a metal lens mount, similar build quality to the EF 28-105 and fits into the second of the six tiers listed above. However, the EF 28-80 3.5-5.6 II USM is an all-plastic cheapie which fits into the first of the six tiers above. (all 28-80 3.5-5.6 lenses from marks II through V are plastic cheapies, in fact) The EF 50mm 1.8, as noted below, is generally considered to be a better lens than the EF 50mm 1.8 II.

Canon also release updated versions of lens hoods using Roman numeral designations. Quite often the mark II version of a hood will fit the same lenses as its predecessor but will have a black flocked interior lining to reduce lens flare.