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Tuesday, April 5, 2011

Landscape Lens Tech

What makes a good landscape lens?

Labels: LensesGear

This Article Features Photo Zoom
Contrast And Color
A good landscape lens should produce good contrast, a function of its design and components, and the coatings applied to the surfaces of the lens elements. Each glass-to-air surface reflects some light, and some lenses—especially zooms—have many elements and thus many such surfaces. This reflected light isn’t transmitted to the image sensor or film, and the light loss can be considerable with high-element-count lenses. These reflections within the lens also cause flare and ghosting (as does flare from an uncoated front element).

Good multicoatings greatly improve light transmission and reduce flare and ghosting. Higher-end lenses have the best coatings. Canon’s SWC (Subwavelength Structure Coating) and Nikon’s NCC (Nano Crystal Coating) use nanometer-scale structures to provide very effective control of reflections, flare and ghosting. Lens manufacturers also design internal baffling to minimize internal reflections and flare. Of course, a landscape lens should produce accurate colors. This, again, is an attribute of the lens design, composition of the elements and coatings.

Zoom Or Prime?

AF-S Nikkor 14-24mm ƒ/2.8G ED
We were surprised a couple of years ago when we polled a number of pro landscape shooters to see what their favorite landscape lenses were and they came up with 16 zooms, two tilt/shifts and a full-frame fisheye—not a prime wide-angle among them.

Naturally, one’s choice of focal lengths for landscapes depends largely on how one sees landscapes, but the large number of zooms—and not just wide-angle zooms—indicates that a goodly number of pro landscape specialists see landscapes in a variety of ways.

Most people think of wide-angles when they think of landscape lenses, and many landscapes are photographed with those. But many strong landscapes are shot with normal and longer lenses as well.

AF-S Nikkor 24mm ƒ/1.4G ED
It’s a matter of framing and perspective. The focal length of the lens (along with the sensor or film format with which it’s used, and the distance from the subject/scene) determines the framing of the image. The distance determines the perspective—how large closer subjects appear relative to more distant ones, and how much space there appears to be between them. We generally move closer when using a short focal length, and this expands perspective. Conversely, we generally use longer focal lengths from farther away, and this compresses perspective. A zoom lens lets you change the framing (but not the perspective) when you can’t move closer or farther, and lets you do it without exposing your image sensor assembly to dust as changing lenses would do. The zoom also lets you move closer or farther away and then reframe as desired, even if that requires an in-between focal length not available in prime lenses.

Historically, prime (single-focal-length) lenses have been the best choices for landscapes because zoom lenses produced noticeably worse image quality. After all, it’s tough enough to correct all those aberrations for a single focal length; when you have to do it for a whole range of focal lengths, that really complicates things.

Computers and advanced ray-tracing models came along, fortunately, allowing lens designers to perform complex calculations and test designs far more quickly. And the creation of exotic lens elements became more widespread and less costly. A major result is that today’s best zoom lenses are quite capable of turning out pro image quality throughout their focal-length ranges. As noted earlier, today, many pro landscape photographers work with DSLRs and zoom lenses, mostly the higher-end pro zooms.


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