[Parts I and II are here—also, don't neglect to read Moose's excellent "Featured Comment" under that post, as it usefully updates these now 6-year-old articles.
Copyright 2008, 2014 by Michael C. Johnston. All Rights Reserved.]
III. Lenses in Use
It seems to me that there are two ways to use lenses intelligently, with conscious and informed knowledge of their imaging properties. The first is to learn the specific strengths and weaknesses of specific lenses, and beware of pictorial situations that won't match well with your lens's strengths or that will expose its weaknesses too unfavorably. The example I always give of what I mean is that many lenses have a lot of falloff wide open. But in many cases when you use a lens wide open, it's in "available darkness" situations with a central subject and nothing but darkness in the corners of the frame. No harm, no foul. If you know a lens is weak wide open, avoid using it that way! You can't always do so, but often you can. If you know the imaging properties of a lens, you can almost always "play to its strengths" and minimize its weaknesses. After a while this becomes habit.
Zander in Werner's garage. The lens and aperture used in this picture might result in falloff (vignetting) in the corners. But who could tell? No harm, no foul. In many way it's possible to mask or disguise the evidence of the performance shortcomings of even fairly poor lenses—but only if you know where those shortcomings are likely to show up.
The other strategy would be to pick a good lens, satisfy yourself that it behaves reasonably well in most situations, and then don't worry about it—shoot freely and take what it gives you.
To split the difference, in effect, a decent seat-of-the-pants working principle might be to "seek the middle" or avoid extremes where possible. That is, if you return to my original ten points for how to optimize a lens's performance, in Part I, you'll notice that most of the recommendations involved selecting a middle value and that most of the ways to "stress" a lens involve pushing it to one sort of extreme or the other. If you just keep this basic principle in mind—middle apertures, middle distances, middle of the zoom range on zoom lenses (at least, back off just a tad from the extremes), moderate contrast subjects, straight-on angles to your subject matter, middle ISO values on your digital camera, etc.—you'll have a decent shot at getting better optical performance out of your lenses.
IV. State of the Art
As I said at the outset, almost all lenses have a "sweet spot" where they will give their optimum results, and those optimum results are almost always excellent. The worse the lens, the more performance suffers in various ways as you move away from that sweet spot. What modern lensmakers work toward, and what you pay for in a really good modern lens, is performance that stays consistent and robust as you move increasingly away from that optimum. A really good lens is one that almost has no sweet spot because it's so consistently excellent under all conditions. It relieves you of the obligation of learning all its foibles because it basically doesn't have any. It will never let you down.
Take as examples the Nikon Nikkor AF-S Nikkor 24–70mm ƒ/2.8G ED or the Canon EF 24–70mm ƒ/2.8L II USM. Among the world's most beautiful camera lenses, they are best suited for use on full frame 24x36mm DSLRs. Neither lens imparts magical qualities to your pictures—they will not cut your eyeballs with zippety-zappety contrast or nuke your subjects with the X-ray vision of super-high resolution in just the axial zone; rather, these lenses are "merely" magnificently, supremely difficult to stress. Within physical limits (by which I mean, putting heads in the corner of the frame at 24mm will still result in perspective distortion, diffraction is still diffraction, and so forth), you may do almost anything either lens is capable of doing without negative optical consequences. Both foreground and background bokeh are subtle, gentle, and unobtrusive, especially for zooms, and is especially impressive with the lenses wide open, where even some good lenses are let down by some ugliness in the out-of-focus rendering. You may use any aperture and any focus distance with virtual impunity. And, assuming you can meter properly, you may put light sources in pictures virtually without fear: flare resistance is excellent and the flare that occurs is reasonably picturegenic (if that's a word; if it's not, it should be). The lenses' imaging properties are remarkably stable across the frame and throughout the zoom range. Both lenses are beautifully built and most likely can be depended upon to keep delivering their marvelous results imperturbably over time and in the face of hard use.
The more you understand about how lenses typically behave, the more you are likely to be impressed by lenses of the quality of these, especially as time wears on and you become more and more familiar with the one you own. Simply magnificent achievements of the lens designer's and maker's craft, richly deserving of the term "state of the art."
V. The Big Caveat
The big elephant-in-the-room qualifier: good lenses don't guarantee good pictures. Good optical properties are scientifically measurable, but good pictorial qualities are not! In fact, given visual sensitivity and sophistication and some luck, photographers can and often do use the bad or flawed properties of poor lenses to good pictorial effect—as Holga, Diana, Lomo and toy camera aficionados do regularly.
Conversely, the finest lens in the world is "nothing special." That is, using it for your pictures is no guarantee that your pictures will be any good at all. In fact, using the world's finest lens is no guarantee that your pictures will even be optically good, since equipment is only half the battle—the other half being your technique. A great lens + poor technique = a technically poor picture. And even a technically excellent picture is not necessarily an excellent picture.
I've found it most amenable to think of lenses and their properties as a hobby somewhat apart from, and ancillary to, my practice of photography. I get pleasure out of understanding how my lenses are responding to and recording the visual world, but that pleasure isn't always an integral part of the visual content and (especially) the artistic effect of pictures. Understanding how lenses work, however, can help you solve specific problems, apply specific solutions, and generally avoid the pitfalls of unpleasant optical surprises and disappointing performance. And the best way to understand how a lens works? Stress it, and see how it does. Owning a fine lens can be a source of pride and possibility, but only if you learn it well.
Copyright 2008, 2014 by Michael C. Johnston. All Rights Reserved.
Original contents copyright 2014 by Michael C. Johnston and/or the bylined author. All Rights Reserved. Links in this post may be to our affiliates; sales through affiliate links may benefit this site.
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