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The primary difference between zoom vs prime lenses is that \u201czoom\u201d lenses that have a variable focal length, while \u201cprime\u201d lenses have a fixed focal length. Many people mistakenly equate \u201czoom\u201d with \u201ctelephoto zoom,\u201d but that\u2019s not the case \u2014 there are wide angle and normal zooms as well. Zooms are very popular these days and most of you are probably using them, but as anything in life they have pluses and minuses and I\u2019d like to inform you of some of the issues involved in choosing one type over the other.<\/p>\n
Let me warn you at the outset that I am biased in favor of prime lenses. Let me also point out that I am photographically a fundamentalist and I don\u2019t wish my particular forms of kookiness on anyone else. Just because my personal style of photography is painstaking and deliberate, perfectly suited to prime lenses, doesn\u2019t mean that you should emulate my choices. Indeed, many if not most top pros use zooms. But my observations may give you information that will help you make an informed choice of what is right for you.<\/p>\n
The most obvious advantage of a zoom lens is that one lens covers many focal lengths, replacing many prime lenses. You don\u2019t have to pay for or carry around the weight of the extra lenses, nor do you have to incur delays from changing lenses. Just twist or slide a collar, and instant focal length choice is yours. Moreover, you can precisely select any focal length at all that is within the range of the zoom, whereas with prime lenses you are stuck with only certain, fixed choices.<\/p>\n
Modern zooms also often test on optical benches to be as sharp as prime lenses. Early zooms were optical disasters, but nowadays they can be of fine quality (although clunkers still exist).<\/p>\n
So what\u2019s not to like? Let\u2019s start with that optical resolution. While the best zooms can test to be as sharp as prime lenses, my experience and that of many others is that they still don\u2019t offer images as \u201ccrisp\u201d as those from prime lenses. What I believe is going on is that there are two things that go into making a picture look sharp: resolution \u2014 what level of detail can be discerned, and contrast \u2014 how well the bright and dark areas are preserved.<\/p>\n
A lens with great resolution but poor contrast will show detail, all right, but it will be all muddy and mid-toned. The resulting image is not pleasing, even though the resolution, technically, is there. It is my belief that zooms, which contain more optical elements than prime lenses, have enough internal light scattering from all those optical surfaces that their contrast suffers, and thus the resulting images lack \u201csnap.\u201d In other words, there is more to judging a lens than it\u2019s resolution, and I think that prime lenses win over zooms in terms of overall image quality due to their better contrast. Those extra optical elements also make zooms more prone to flare.<\/p>\n
Now, whether the (possibly minor) optical advantage of prime lenses is worth putting up with their inconvenience is a matter of personal taste. For my work, where I am trying to eke out the best possible image in sizeable enlargements, it\u2019s worth it, but most people are not in that boat.<\/p>\n
There are other reasons why I don\u2019t like zooms that might or might not matter to you. A one-touch zoom is subject to \u201czoom creep\u201d if the lens is pointed up or down: gravity slowly moves the zoom collar if the collar drag is not properly adjusted. Also maddening for me is that, for most (but not all) zooms, the f-stop changes as you zoom.<\/p>\n
I usually set my exposures manually, and if I have an exposure figured out and I decide to zoom, I have to make sure I adjust the exposure accordingly. I\u2019m busy enough when I\u2019m making images; that\u2019s more than I care to keep track of. In addition, the front element of some zooms rotates as the lens zooms, a disaster if you\u2019ve got a polarizer or a split neutral density filter already adjusted the way you want it.<\/p>\n
And there\u2019s more. The closest focus distance of zooms tends to be farther away than that of prime lenses. Zooms tend to have slower maximum apertures than prime lenses. I\u2019ve never trusted my ability to maintain precise focus while zooming a one-touch zoom. And a lens shade, which you should always use to minimize flare, is problematic on a lens whose focal length is variable: except for a few fancy lenses that have an automatically variable lens shade built in, you are stuck using a shade appropriate for the widest possible angle of view and it won\u2019t be sufficient at the longer focal lengths.<\/p>\n
My final reason for disliking zooms is quirky and personal. For me, all that flexibility that zooms offer, paradoxically, is too much. There are a lot of choices to be made when creating images, and I am one to fret over options. So I fare better if the process is simplified. I do best if I can simply say \u201cthis is a wide angle image,\u201d or \u201cthis requires my longest lens.\u201d I judge how I want space to feel in the image (which is a key effect of different focal lengths), opt for the appropriate lens, and get on with it.<\/p>\n
No fussing, no fretting, I just choose a lens and get on to the next decision. This approach is not without risk: I have lost images that required the precise cropping permitted by a zoom . . . but surprisingly rarely. For me, it works best if I stay with prime lenses.<\/p>\n