All animals are equal but some are more equal than others, as a certain Mr Orwell once wrote. If he had been a photographer, he may well have substituted the word animal for the word lens. You see in terms of what lenses do, they are all equal, their sole purpose is to focus the light from the scene in front of us onto the sensor or film inside our camera. Today, however, we will take a look at what makes some of these lenses more equal than others.
As with most things in life, lens glass comes in varying degrees of quality. The very best glass, the stuff found in the top pro-end lenses has a multitude of advantages, higher manufacturing tolerances, higher grade source materials and of course, the coatings. Often you will see lenses will have one or more acronym pasted to the sides of the barrel. These often denote which coatings have been applied to the lens surface. The coatings are there to improve image quality by reducing flare, reflections both internal and external and boosting contrast and color. You will often find the better quality lenses have several of these coatings.
Lens design is a highly complicated and precise feat of engineering. The simple fact is that the design of a typical kit lens will in no way match the design of a higher end professional lens. The high end lenses tend to use more elements – the number of individual glass optics, in more groups – the number of elements grouped together. These combinations have been carefully engineered to significantly reduce typical lens distortions such as pin cushioning, barrel distortion and chromatic aberration. Beyond that, the overall construction of the lens will tend to use metal allow for the barrel rather than plastic and much more refined focus and zoom rings. The effect of this is to give the photographer a more precise control over the use of the lens.
Another important area where some lenses excel over others is in their maximum aperture or lens speed. Typically kit standard kit lenses use apertures of between f4 and f5.6, whereas a professional zoom lens of similar range will be f2.8, maybe even wider. This has two important bonuses, the ability to shoot in lower light without increasing film speed and the possibility of a shallower depth of field. Another factor here, with zoom lenses is that higher end zooms will generally have a fixed aperture, that is to say as you zoom the lens the maximum aperture will remain the same. This is very often not the case with cheaper zooms.
Prime vs. Zoom
Whilst many of use these days enjoy using zoom lenses, the fact remains that prime lenses – lenses with a fixed focal length, for the most part will have a better image quality than an equivalent level zoom. The primary reason for this is that the optical construction does not have to be so complicated meaning that there are less lens elements and groups required. A by-product of this simpler design is that prime lenses often have a significantly wider maximum aperture than their zoom counterparts as well as, very often, a significantly lower price as well.
Prime lenses require less complex elements. Photo by Derrick Austinson Photog
The concept of Bokeh is, perhaps as strange as the word itself. Coming originally from Japanese, Bokeh is used to describe the aesthetic quality of the blur in the out of focus areas of an image. Now if that sound like it might be somewhat subjective, you would be right, but the simple fact is, some lenses produce a beautiful creamy out of focus feel at wide apertures and some simply don’t. It's down to you to decide if you like the Bokeh from a particular lens.
Bokeh changes with different lenses. Photo by Agnisoonu K
Closest Focus Distance
Another product of high quality lens design is often the ability to focus on closer subjects than equivalent cheaper lenses. This is particularly relevant when using telephoto primes or zooms where you may find that with some lenses, you just cannot get close enough to your particular subject.
The quality of the lens that you put on your camera will have a direct effect on the quality of your final image. If you shoot only to display your images on screen then a kit lens will probably suffice. However, if you strive for higher quality, you will soon find that all lenses are really not equal. A higher end lens will not only give you better image quality but open the doors of greater creative possibility by giving you the tools of shallower depth of field and better Bokeh.
You might think that it is not worth the expense of buying a better lens but think of it this way. Lenses are on a much slower technological timeline. Whilst your camera might be obsolete in two years, a good quality lens will last twenty years or more. Providing that your chosen camera manufacturer, remains consistent with their lens mount, that expensive lens will seem remarkable value.