Wide-Angle Zooms

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Wide-angle lenses are essential landscape photography tools for their ability to take in epic vistas and allow you to move in close to emphasize a foreground object while still showing enough of its surroundings to give a feel for the location.

Clockwise from top left: Nikon AF-S Zoom-Nikkor 14-24mm ƒ/2.8G ED; Tokina 17-35mm ƒ/4 PRO FX; Tamron SP 10-24mm F/3.5-4.5Di II LD Aspherical; Canon EF 17-40mm ƒ/4L USM

Wide-angle zooms offer a number of advantages. For one, they provide an entire range of focal lengths in a single, convenient package. A 16-35mm zoom not only gives you 16mm and 35mm, but every focal length in between, including the popular 18mm, 21mm, 24mm and 28mm. A second wide-angle zoom benefit is instant access to any of these focal lengths. Just twist the zoom ring, and you can crop the scene as you wish—much quicker than removing one lens, attaching another, and seeing if that meets your needs. With DSLRs, equally important is that zooms minimize lens changes in the field, which, in turn, minimize dust spots on your image sensor.

To choose the best wide-angle zoom for you and your photography, there are some key factors to keep in mind.

What's Wide Angle For Your Camera Format?
Longtime 35mm photographers think of lenses from 35mm and shorter as wide-angles because these focal lengths produce a wider angle of view than a focal length equal to the format's 43.2mm diagonal measurement (or the 50mm focal length popularly considered "normal" for the 35mm format). But a focal length's angle of view also depends on the format of the camera with which it's used. With film, this wasn't a big deal. All 35mm SLRs produced 36x24mm images, so a given focal length on one 35mm SLR would produce the same angle of view on any of them.

With digital SLRs and mirrorless digital cameras, sensors come in different formats, and each produces a different angle of view with a different focal length because it "sees" a different portion of the image produced by the lens. The sensor in a "full-frame" DSLR is the same size as a standard 35mm image frame, so a given focal length on a full-frame DSLR will produce the same angle of view as it would on a 35mm SLR. The sensors in APS-C DSLRs are smaller (23.6x15.6mm or so vs. 36x24mm), so they "see" a smaller portion of the image produced by a given lens. APS-C digital cameras have a 1.5x crop factor, so a given lens on an APS-C camera shows the field of view of a lens 1.5 times longer on a full-frame camera. A 35mm "wide-angle" lens becomes a 53mm "normal" lens when used on an APS-C camera for framing purposes.

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LEFT: Sigma 12-24mm ƒ/4.5-5.6 DG HSM II; RIGHT: Sony Carl Zeiss 16-35mm ƒ/2.8

The Four Thirds System (and Micro Four Thirds System, which uses the same 17.3x13.0mm sensor size) has a 2x crop factor. Any given focal length used on a Four Thirds camera frames like a lens of twice its focal length on a full-frame camera. That is, a 35mm lens used on the Four Thirds System camera frames like a 70mm lens on a full-frame camera.

The point here is that which focal length constitutes "wide-angle" varies with camera format. For 35mm SLRs and full-frame digital cameras, lenses of 35mm and shorter are wide-angle, and lenses of 21mm and shorter are superwide-angle. For an APS-C camera, the equivalent focal lengths would be two-thirds of those for full-frame—wide-angle starts at 24mm and superwide-angle at 14mm. For Four Thirds cameras, the equivalent focal lengths would be half of those for full-frame—18mm for wide-angle, 11mm for superwide.

Exotic Glass Elements
Wide-angle lenses are prone to spherical aberration (light rays traveling through the edges of the lens don't focus at the same plane as rays traveling through the lens closer to its center), especially fast wide-angles with their large front elements, so lens designers include one or more aspherical elements to minimize this. Designers also employ extra-low-dispersion elements with such designations as ED, UD, SUD, FLD, SD, LD and SED to minimize chromatic aberrations (different wavelengths of light focusing at different distances behind the lens or at different distances from the optical axis). All of the wide-angle zooms listed in our lens chart incorporate both aspherical and extra-low-dispersion elements.

Distortion & Perspective
In theory, true wide-angle lenses are rectilinear; they reproduce straight lines in the scene as straight lines no matter where they appear in the image frame. In practice, wide-angle lenses, and especially superwide-angle lenses, do bend straight lines near the frame edges: barrel distortion. Fisheye lenses aren't rectilinear; they bend straight lines outward unless those lines pass right through the center of the image.

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LEFT: Pentax DA 12-24mm ƒ/4.0 ED AL (IF); RIGHT: Olympus Zuiko Digital 7-14mm ƒ/4.0 ED

Another type of wide-angle "distortion" actually isn't distortion; it's just the effects of perspective. When you move very close to an object with a wide-angle lens, in the resulting image and in the viewfinder, the object will appear huge compared to more distant objects in the frame. The nearby object itself can appear elongated. In both cases, this isn't distortion; it's simply the way things look at such close range.

If you have two equal-height statues 10 feet apart and photograph them from 100 feet away, the distance to the near statue is 100 feet and the distance to the far one is 110 feet, a difference of 10%. Thus, the closer one will appear 10% closer and 10% larger in the image. If you move to 10 feet from the near statue, it now will be 10 feet away and the far one will be 20 feet away—twice as far. In the resulting image, the near object will appear half as far and twice as large as the distant statue. Move to two feet from the near statue, and it now will be 2 feet away and the distant statue will be 12 feet away—six times as far. In the resulting photo, the near statue will be six times as large as the far one and appear six times closer. That's not distortion; that's the way it really is. (It's why portrait subjects' noses appear pointy when you shoot at very close range with a wide-angle lens and why headshots are best done from farther away with short tele lenses.)

"Wide-angle distortion" is really due to the close shooting distance. You just notice it more with wide-angle shots because you're generally shooting from closer range with a wide-angle lens, and longer lenses crop the image more tightly, cropping out some of the "distortion."

You can put these effects to good use in your landscape images, emphasizing a foreground object and the distance between it and more distant elements in the scene.

Controlling The Horizon
There's a general rule of thumb for landscapes that says you shouldn't put the horizon line across the middle of the frame. If the land is the most important part of the scene, place the horizon high in the frame to emphasize it; if a spectacular sky is most important, place the horizon low in the frame to emphasize the sky.

Placing the horizon high or low in the frame will tend to curve it, especially with lower-cost wide-angle primes and wide-angle zooms. When contemplating a potential wide-angle zoom purchase, shoot a few frames with the horizon high and low in the frame, and see how much curvature there is. If you do wind up with a lens that curves the horizon a lot, you can minimize the effect by composing with the horizon a bit closer to the center of the frame.

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Lens Speed & Depth Of Field
Although fast lenses are larger, heavier and more expensive than slower ones, they're a better choice for serious photography. As you know, an ƒ/2.8 lens will let you shoot in dimmer light, or at a higher shutter speed in a given light level, than a slower zoom will. And the faster lens will provide better results in selective-focus work because it can produce more limited depth of field when you want that. The faster lenses also provide a brighter image in a DSLR's viewfinder for easier composing and manual focusing/autofocus checking.

Low-light performance is only part of the story. You may be thinking that you don't need a fast lens because you'll be doing most of your landscape shooting at smaller apertures for maximum depth of field, but that's not necessarily the case. The interplay between lens speed, depth of field and the sweet spot come into the equation. In fact, because ƒ/22 is such a small aperture with a wide-angle lens, your maximum depth of field is compromised by diffraction-induced softness. With a fast wide-angle lens, you can get a lot of depth of field at ƒ/8 or even ƒ/5.6, and you'll be shooting at the sweet spot where the lens is sharpest. With a slower lens, you may need to stop down to ƒ/11 or ƒ/16 to be in the sweet spot, but your photograph will be affected by diffraction. For more information, see the sidebars "Sweet Spot" and "Focal Ratio" in this article.

How To Interpret MTF Curves The gold-standard tool for evaluating a lens is the MTF graph, but for most photographers, MTF data is difficult to interpret, to say the least. An MTF (Modulation Transfer Function) curve is basically a graph that shows how well a lens or an entire optical system transfers the contrast of an original target to the image of the target. The target is a series of bright and dark lines, which gradually become finer and finer, i.e., starting from just a few bright/dark line pairs per millimeter and progressing to 100 line pairs or more per millimeter. An ideal lens/system would reproduce the test chart exactly as it is in real life. A typical MTF curve plots contrast along the vertical axis and distance from the center of the image frame across the horizontal axis. The vertical axis scale runs from 0 at the bottom (no contrast at all) to 1.0 at the top (indicating the lens reproduces 100% of the target's contrast). The horizontal scale runs from 0 (center of the image frame) to 20 (20mm out from the center) or so, depending on the image format. A chart for a "perfect" lens would show a straight line across the top, meaning the lens reproduces 100% of the test target's contrast all across the frame. Of course, that doesn't happen in real life, so the line on the curve starts out high at the left (representing the center of the image) and curves down as it moves to the right (farther from the image center). As a general rule, MTF lines of 0.8 (80% of the target's contrast) indicate a very good lens; lines around 0.6 (60% contrast) indicate a satisfactory lens (depending, of course, on your idea of satisfactory). A single line just shows lens performance for a single spatial frequency (number of line pairs per millimeter) at a specific aperture (generally, wide open). So manufacturers include lines for two or three spatial frequencies, generally 10 lp/mm and 30 lp/mm, or 10, 20 and 40 lp/mm. The 10 lp/mm lines provide an indication of the lens' contrast, while the 30 and 40 lp/mm lines provide an indication of the lens' sharpness. Generally, thick lines are used on the MTF graph for the 10 lp/mm curve and thin lines for the 30 lp/mm curve. Lines are also shown for targets that are aligned parallel to the format's diagonal (corner to corner) and for targets perpendicular to those. The former are called radial, or sagittal, lines; the latter, tangential, or meridional, lines. These are shown as broken lines on the MTF graph; again, thick ones represent 10 lp/mm readings and thin ones, 30 lp/mm readings. The key here is that bokeh is more pleasant when the radial and tangential curves are similar. Some manufacturers include lines for wide open and a middle aperture (often ƒ/8). These show the effects on performance of stopping the lens down. Lens performance generally increases as you stop them down from maximum aperture, since doing so reduces the effects of various aberrations; then performance decreases as you continue to stop down, and diffraction adversely affects the image. Of course, for zoom lenses, you'll want to see MTF curves for wide, middle and long focal lengths. Bear in mind that, even for fixed-focal-length (prime) lenses, telephotos generally have better MTF charts than wide-angles because wide-angles present more design challenges. If you really want to get into this, an online search for "Zeiss MTF Nasse" will lead you to a thorough two-part illustrated discussion of MTF curves and their ramifications (H.H. Nasse is the author).

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Other Lens Attributes To Consider
Some wide-angle zoom lenses use a twist ring to zoom, while some use a push-pull ring. Either way, the zoom control should operate smoothly, and the focal length shouldn't change when you tilt the camera up or down as much as you're likely to when shooting.

Fast pro zooms can be rather heavy, and this can cause the lens to extend to its longest setting as you walk with the camera on a neckstrap. Some zoom lenses, mostly telezooms, have zoom locks that prevent this from happening.

If you like to move close to a small object to exaggerate its size relative to the surroundings—"close-up wide-angle" shooting—you'll want a lens with a close minimum focusing distance. You also may want to consider the maximum magnification possible with the lens. Wide-angle lenses have short focal lengths and aren't known for their magnification, but one that provides greater magnification can be helpful when you want to get a smaller object as large as possible in the frame.

Lens hoods can reduce flare and, thus, enhance image contrast. But superwide-angles generally don't accept lens hoods because their wide angles of view would cause the hood to appear in the image. Hoods for wide-angles often stick out farther at top and bottom than at the sides since the angle of view is greater horizontally than vertically. Make sure you install this type of hood in the proper orientation or you risk significant vignetting.

Like lens hoods, filters can be problematic when shooting wide. Some ultra-wide-angles don't have filter threads because of the shape of the front lens element and the risk of vignetting. Even if your lens is threaded for filters, look carefully through the viewfinder when using one. Some low-profile filters have narrow rings to avoid vignetting, but even these don't always do the trick, especially at wider apertures. You certainly can use filters, but take extra care when doing so.

Canon EF 24mm ƒ/1.4L II USM; Nikon AF-S Nikkor 24mm ƒ/1.4G ED Wide-Angle Primes While wide-angle zooms offer the benefits of many focal lengths in a single package and the ability to change them without exposing the sensor to dust, wide-angle primes have benefits of their own. They're generally sharper and better corrected for distortion and aberrations than zooms since they must be corrected only for a single focal length. Wide-angle primes are generally faster than wide-angle zooms, useful in low-light situations and for selective-focus work. Wide-angle primes are popular with video shooters, in part because of their wide maximum apertures, useful for creating a cinematic look. Having at least one wide-angle prime in your bag is incredibly useful. Except for the very fastest models, primes are relatively inexpensive, they tend to be very sharp, and they're small and lightweight, making them ideal when you don't want to haul a large heavy zoom.