The Sony FE 100-400mm F4.5 GM OSS ($4,299.99) is an exceptional zoom lens with a focal range that's ideal for capturing field sports, a bright aperture that can handle tough lighting situations, a blistering fast autofocus drive, and teleconverter support in case you need an even tighter angle of view. It's Sony's second E-mount 100-400mm, and sits beside the smaller, more affordable FE 100-400mm F4.5-5.6 GM OSS ($2,799.99) as an upgraded option. The 100-400mm F4.5 will no doubt show up on the sidelines of pro and collegiate sporting events and will please hobbyists with big budgets, too. 

Design: Big, But Not as Heavy as Expected

The FE 100-400mm F4.5 GM OSS is one of those lenses best suited for professional photographers and very serious hobbyists. It's a big lens and expensive compared with others that cover the same focal length, so you'll have to be willing to open your wallet to buy it and lug it around for photography.

(Credit: Jim Fisher)

The zoom's fixed aperture and internal zoom contribute to its 13.0-by-4.8-inch (HD) exterior and 4.1-pound carry weight. It's a big lens for sure, but fairly light for its size. The zoom is internal, which means the lens never gets longer or shorter, which makes it a little easier to manage than you'd expect.

But there's no getting around the fact that the FE 100-400mm F4.5 is a lot more to carry when compared with other 100-400mm zooms for the system. The FE 100-400mm F4.5-5.6 GM OSS (8.1 by 3.7 inches, 3.1 pounds) and Sigma 100-400mm F5-6.3 DG DN OS Contemporary (7.8 by 3.4 inches, 2.5 pounds) are a lot easier to carry, even though both telescope when zoomed in.

(Credit: Jim Fisher)

The 100-400mm focal range is especially useful for photographing field sports, and I expect that's the audience Sony had in mind when developing the lens. Typically speaking, you'll want something shorter and brighter for events and portraiture—the FE 70-200mm F2.8 GM OSS II is the de facto standard. And for wildlife, you'll likely want a lens with more reach, like the FE 200-600mm F5.6-6.3 G OSS and FE 400-800mm F6.3-8 G OSS.

With that in mind, the FE 100-400mm F4.5 GM OSS's size and weight aren't big drawbacks. It's too big a lens to hang from your side when photographing a wedding reception, but right in line with the sizable glass that you see the pros using to photograph MLB and NFL games. It's lighter to carry than either of Sony's speciality wildlife zooms, too—the FE 200-600mm tips the scales at 4.7 pounds, and the FE 400-800mm comes in at 5.5 pounds.

(Credit: Jim Fisher)

The lens is compatible with both of Sony's rear teleconverters. With a 1.4x, it turns into a 140-560mm F6.3, and with a 2.0x, it's a 200-800mm F9. That makes it an appealing option for photogs who cover sports from the sidelines and want the flexibility to use the same lens for wildlife shots too. The more affordable FE 100-400mm F4.5-5.6 GM OSS also works with teleconverters, but doesn't gather as much light when zoomed in, so it dims to 560mm F8 and 800mm F11 with a 1.4x or 2.0x teleconverter, respectively.

(Credit: Jim Fisher)

As you'd expect given its price point, the FE 100-400mm F4.5 GM OSS features a white barrel exterior, a design choice that's as much about marketing as it is about keeping the internal optics cool in hot, sunny environments. It also offers full dust and splash protection, with a fluorine-treated, grease- and water-repellant front element.

(Credit: Jim Fisher)

The 100-400mm F4.5 has a dual filter system. Its front element works with 95mm threaded filters, a large size that can be pricey. Plus, it has a rear drop-in filter holder that works with the far more affordable 40.5mm size.

The lens ships with a soft carrying case, front and rear caps, and a reversible hood. The hood adds some length while effectively protecting the front element from damage and reducing flare from light entering at a steep angle. It also has a tripod foot, a must-have to keep its center of gravity balanced when using a tripod or monopod. The tripod collar and foot rotate a full 360 degrees and cleverly include a switch to change the collar between continuous, silent rotation and 90-degree detent clicks. It also has painted dots at 90 degrees so you can level the lens visually.

(Credit: Jim Fisher)

The foot includes some padding, so it's comfortable to use as a handhold, but it does not have the dovetail cuts to fit an Arca-Swiss tripod head. You'll want to add a quick-release plate or replace the foot with an aftermarket alternative if you use Arca-Swiss gear. There's no quick-release to remove the foot, so you'll need a Torx screwdriver if you decide to swap it out. The collar includes a thumb screw to lock it into place and two strap lugs.

Controls: Everything At Your Fingertips

Pro telephoto lenses usually have more buttons, toggle switches, and control rings than shorter focal lengths and primes, and the FE 100-400mm F4.5 lives up to that expectation. The extra on-lens controls make sense; the scenes that you'll capture with a long telephoto can be technically demanding, plus there's plenty of room on the barrel.

(Credit: Jim Fisher)

The FE 100-400mm F4.5 includes three discrete control rings. Its manual focus ring is positioned just ahead of the tripod collar. It's about an inch wide and turns comfortably. The lens supports full-time manual focus in any autofocus mode when DMF is turned on, a plus for wildlife photography. If you're trying to get a picture of a critter in brush or branches, you can give the camera's autofocus system a little help by manually bringing it into focus if it gets confused by a foreground obstruction.

(Credit: Jim Fisher)

The zoom ring is just ahead of focus. It's about three inches long, with a tapered design that adds some comfort when setting the zoom. The zoom has two tension settings, Smooth and Tight, which are set with a toggle switch. In the Smooth mode, I can change the focal length with my fingertips, which is a plus for photographing sports and other scenes where you'll frequently change focal length. On the downside, due to gravity, the focal length will change if you tip the lens down toward the ground in Smooth.

(Credit: Jim Fisher)

Switching to the Tight setting keeps the lens set where you've left it, but requires a little more torque to change the zoom—you'll want to get a good grip with your thumb and all of your fingers with the Tight tension. I like using this for wildlife, though. I'm almost always at 400mm for birds and smaller animals, and I don't have to worry about the lens zooming out to a wider focal length when it hangs by my side.

(Credit: Jim Fisher)

The lens also has a Function ring, located just ahead of the zoom, a feature that we've seen on Sony's exotic tele lenses, including the FE 300mm F2.8 GM OSS, FE 400mm F2.8 GM OSS, and FE 600mm F4 GM OSS. The Function ring is dedicated to powered manual focus with this lens. Twist it right and the focus moves closer, or left and the focus shifts further away. It's a handy tool for video shots where you want to make a slow, smooth rack between subjects for narrative effect. There's only a little bit of change in angle of view (called focus breathing) when shifting between the nearest and furthest point of focus, and none at all if you turn on Sony's in-camera Breathing Correction feature for video. The 100-400mm F4.5 is a solid choice if you want to use a telephoto focus rack shot in a project.

(Credit: Jim Fisher)

The 100-400mm also has four Focus Hold buttons. They are just ahead of the Function ring and set 90 degrees apart. While they are configurable, all four are always mapped to perform the same function. By default, that's AF-L (Autofocus Lock), but it's easy enough to change them to AF-ON or another function via the camera menu. I set them to engage the Speed Boost function, which ramps up continuous drive to its fastest rate (30fps on the a7R VI, with which I reviewed the lens) on demand.

(Credit: Jim Fisher)

There are also five toggle switches that set focus and stabilization options. AF/MF is self-explanatory; it switches the lens between autofocus and manual focus. Full Time DMF lets you use the manual focus ring in any autofocus mode when it's set to On, and restricts manual focus control to MF when it's set to Off. And the Full/Infinity-4m switch is a focus limiter, which lets the lens focus across its entire range in Full, and restricts autofocus to distant subjects when set to its Infinity-4m position. OSS lets you turn the Optical SteadyShot stabilization on or off, and has a corresponding Mode 1/2/3 setting that optimizes the stabilization for static subjects (1), panning laterally (2), or scenes where you'll pan both laterally and vertically (3).

(Credit: Jim Fisher)

Really, the only thing missing from the lens is a Preset focus function, and to be honest, I'm a little surprised that Sony left it out. Preset focus lets you save a focus distance to memory so you can drive focus back with a button press or, for Sony lenses that have it, a twist of the Function Ring. It's a useful feature for sports and bird photography as it lets you save the distance from the camera to a spot on the field or a favored perch and snap back to it with no delay. To date, only the Sony FE 400mm F2.8 GM OSS and FE 600mm F4 GM OSS include it.

Autofocus: Fast, Reliable, and Accurate, With Good Macro

The FE 100-400mm F4.5 uses four XD linear motors to silently drive autofocus. Calling the system fast is an understatement. Focus jumps between a close and distant target in an instant. The a7R VI camera I tested it with tops out at 30fps, and I had great success capturing sharp images of songbirds bouncing between branches. I didn't notice any slowdown when using a teleconverter either.

(Credit: Jim Fisher)

The lens focuses as close as 2.1 feet at 100mm. That doesn't sound very close, but since the distance is measured from the camera sensor, it provides about a foot of working distance from the front glass. The minimum focus distance gets longer as you zoom in, but matches up with the change in angle of view to deliver 1:4 life-size magnification through its entire zoom range, an excellent figure for a zoom. Adding a teleconverter doesn't change the focus distance, so you can get closer with a 1.4x (1:3 life-size) or 2.0x (1:2 life-size) extender.

(Credit: Jim Fisher)

As good as the FE 100-400mm F4.5 is for macros, it is one area where the FE 100-400mm F4.5-5.6 GM OSS actually performs better. The F4.5-5.6 edition supports 1:2.9 reproduction without a teleconverter.

Image Quality: Nearly Perfect, With a Little Character in the Bokeh

I paired the FE 100-400mm F4.5 GM with the 60MP a7R IV and Imatest software in the lab, and used it with the 66MP a7R VI in the field to get a handle on its image quality. I chose the a7R IV because we've standardized our FE lens lab tests with the body. The FE 100-400mm F4.5 puts up fantastic numbers in an SFRPlus evaluation, scoring near the top of the excellent range (4,800-4,900 lines) wide open at 100mm and 250mm on our large, high-resolution test chart.

(Credit: Jim Fisher)

I'm not able to frame up a test shot at 400mm with that chart, but with my telephoto chart, I see scores in the 4,300-4,600 range at 100mm, 250mm, and 400mm wide at maximum aperture. Put in plain language, the 100-400mm F4.5 is about as sharp as they come when shot wide open. Images I captured in the real world reinforce the lab results—I can practically count the individual feathers on songbirds. I also saw excellent results when using the lens with the Sony 1.4x rear teleconverter, and I can't find any visual evidence of the extender harming image quality.

(Credit: Jim Fisher)

Resolution holds steady through f/8, declines slightly from f/11-16, and falls off sharply at the smallest aperture settings, f/22-32. It's wise to avoid using a lens at tiny apertures, as it causes diffraction, an optical effect that scatters light as it passes through the closed-down 11-blade diaphragm. The scattering effect softens details and is simply unavoidable—there's no getting around the laws of physics.

(Credit: Jim Fisher)

The lens shows a little bit of pincushion distortion at longer focal lengths in Raw format, but in-camera corrections squash the issue for JPGs and movies. Adobe doesn't yet have a correction profile to automatically remove the distortion, but I expect one to be available soon after release. Lightroom is updated regularly to add support for new cameras and lenses. There's no sign of a vignette at all, and the lens handles backlit scenes and photographs into the sun without showing any notable flare.

(Credit: Jim Fisher)

The FE 100-400mm F4.5's telephoto optics and bright aperture work together to capture images with a shallow depth of field and softly defocused backgrounds. The background blur is generally quite smooth, with no signs of false color. It's not quite perfect, though; there is a slight onion skin texture in defocused highlights, but it's very minor.

(Credit: Jim Fisher)

If there's a complaint to be made about the optics, it's in the bokeh. Some of its defocused highlights show a bright center and edges with a slim dark ring in between, which can make backgrounds distracting in some scenes. It's a situational issue; you won't see it in every scene or even in every highlight. But if you make an image with a lot of bright highlights behind the plane of focus, or with repeating patterns like dewy grass, small tree branches, or complex foliage behind your subject, you'll see a little more distracting texture in the bokeh versus lenses that draw highlights with soft, feathered edges.

(Credit: Jim Fisher)

I'm splitting hairs here, as many telephoto lenses show more characterful bokeh, and the FE 100-400mm F4.5 GM OSS does a better job of smoothing out the backdrop than either the FE 100-400mm F4.5-5.6 GM OSS or Sigma 100-400mm F5-6.3 DG DN Contemporary. If you want a telephoto that renders background elements into nothing, consider the Sony FE 300mm F2.8 GM OSS. Its F2.8 aperture delivers an especially shallow depth of field, but it costs more than the 100-400mm F4.5 and isn't as versatile as a zoom lens.