Sony FE 100mm F2.8 STF GM OSS Lens Review

Do you like your image backgrounds to be rendered with high quality? You should, the entire frame matters, and backgrounds (and foregrounds) typically comprise a significant percentage of the frame. Especially in this regard, the Sony FE 100mm f/2.8 STF GM OSS Lens is special. Thanks to an optical apodization (APD) element, few lenses can create a background and foreground blur quality as good as this lens can, especially at its wider apertures.

Combine the special background blur quality characteristic with outstanding image quality and you get a lens that begs to be used for purposes a 100mm prime lens would not otherwise be selected for. Wearing the GM badge, this lens is designed with professional use in mind. The name says f/2.8 but with this lens, some explanation is required. Read on.

Focal Length

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Once again, we're reviewing a prime lens and with only a single focal length available, the "What is the 100mm focal length good for?" question is relevant and the standout use for the 100mm focal length is portaiture.

The 85mm through 135mm focal length range (after FOVCF is factored in) is classically considered ideal for portraits, for reasons including perspective and working distance. A 100mm lens hits just under the midpoint of that range on a full frame mirrorless or DSLR camera with the 150mm angle of view equivalent on an APS-C 1.5x body being a bit narrower and still great for portraiture, especially for tightly-framed portraits. An APS-C format camera requires a longer working distance to get the same framing as a full frame model and therefore will have more depth of field and a less-strongly blurred background at the same aperture.

The "portrait photography" designation is a broad one that covers a wide variety of potential still and video subject framing (from full body to head shots) and a wide variety of potential venues (from indoors to outdoors). Portrait subjects can range from children to seniors and from individuals to groups. Think engagements, weddings, parties, events, families, small groups, senior adults, fashion, documentary, lifestyle ... all are great uses for the 100mm focal length. There is often adequate space in even a small studio for portraiture with a 100mm angle of view. Entire portrait sessions can be done, inside or outside, with a 100mm lens.

My typical subjects were not available for portrait sessions during my window of opportunity with this lens, so I turned to the horses instead. Pay attention to the background blur quality, though it is not as easy to see in the reduced size images shared here.

A note about head shots: everyone loves head shots, but it is easy to get too close to the subject's head when using a too-wide focal length, resulting in a not-pleasing perspective that usually includes an enlarged nose and reduced-size ears. The tight head shot portrait framing distance provided by the 100mm focal length angle of view on a full frame camera is about as close as I like for this type of image. Being too far away is seldom a perspective problem, though features appear more compressed at longer distances, reducing the feeling of being close to the subject in the result. Communication also becomes problematic as the subject-to-camera distance increases.

I like to argue that people are the most important subjects available. You can't buy stock photos of (most) people and that means portrait photography is one of the most-revenue-producing genres. Producing revenue of course makes a lens purchase much easier to justify. Memories of the special people in your life are priceless.

Regardless of the camera format being used, the 100mm focal length (like most others) can be used for landscape photography. Telephoto focal lengths can fill the frame with color from an only mediocre sunrise or sunset. This lens is an excellent choice for medium-small through large products, commercial and general studio photography applications, some architecture needs and a wide range of other subjects.

Max Aperture

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The product name specifies "f/2.8" as the widest aperture available from this lens. The product images shared in this review reveal that this lens's manual aperture ring is denoted "T", for T-stops, showing the actual amount of light transmission. While this lens technically, by the physical measurement definition, has an f/2.8 max aperture, the T-stop ring stops at f/5.6. The f/5.6 aperture is the widest selectable in-camera and is the widest aperture setting that will show in EXIF data for images captured with this lens. The reason for this has to do with the STF (Smooth Trans Focus) feature provided by an optical apodization lens element.

"An optical APD element is a special type of filter that exhibits gradually decreasing light transmission towards its periphery. It attenuates the edges of point images, resulting in exceptionally smooth, beautiful bokeh in both background and foreground areas with an absolute minimum of double-edge effects." [Sony]

Note that we continue to use the conventional "aperture" (vs. T-stop) designations throughout this review, but from a brightness perspective, this is a T5.6 lens. We'll explore the bokeh in much greater detail in the image quality section. As of review time, 100mm prime lens apertures get as wide as f/1.4 and T5.6 is rather dark.

Being a short telephoto lens, the FE 100 STF can create a strong background blur.

Sony has been featuring an aperture ring on some of their prime lenses including this one, permitting a manually-chosen aperture to be selected. With the ring in the A (Auto) position, the camera controls the aperture setting. All other settings force the aperture to the selected opening and a 2-position switch on the bottom right side of the lens toggles the aperture ring between 1/3 stop clicks and smooth, quiet, non-clicked adjustments, ideal for video recording.

Image Stabilization

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A dark short telephoto lens benefits greatly from image stabilization and this one has it.

Sony marketing touts their cameras as having IBIS (In-Body Image Stabilization), but many of their lenses also feature OSS (Optical SteadyShot). While perhaps not immediately clear, these two stabilization systems are complementary and the 5-axis in-body image stabilization becomes available when used with an α series bodies having that feature.

These stabilization systems significantly increase the versatility of this lens, enabling sharp handheld results to be captured in low light conditions. The difference they make is significant.

Sony does not specify a number of stops of assistance rating for this lens. Shooting handheld under ideal conditions (indoors on concrete), using a Sony a7R III, most of my 100mm images were sharp at 0.1 seconds and enough were sharp at 0.2 seconds to make this exposure duration definitely worth trying.

Those results are far better than I could obtain without assistance. Photographing outside, perhaps in the wind or on unstable footing? Expect to need faster exposures than those I reported. But, also expect a similar amount of assistance from OSS and IBIS as it is still similarly and significantly compensating for shake.

While OSS is great for reducing camera shake-caused blur in images, it is also helpful for precise framing of subjects in the viewfinder. While OSS is active, drifting of framing is not an issue with the viewfinder view remaining well-controlled, not jumping at startup/shutdown and subject reframing being quite easily accomplished.

Handheld video recording is also nicely assisted by OSS and the stabilized composition also provides a still subject to the camera's AF system, permitting it to do its job better.

Note that Sony recommends turning OSS off when using a tripod. A switch on the lens makes this easy to do.

Image Quality

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So, this is an f/2.8 max aperture lens that only transmits as much light as an f/5.6 aperture in a normal lens. The dark wide-open performance is greatly aided by OSS, but ... a lens's optimal image sharpness is typically a stop or two narrower than at its widest aperture. If this lens needed an extra stop or two for sharp performance, it would be really dark.

Fortunately, the Sony FE 100mm f/2.8 STF GM OSS Lens is exceptionally sharp from full frame corner to full frame corner at its widest aperture, f/2.8 or T5.6. This is a impressively high-performing lens.

In addition to our standard lab tests, I like to share some real-world examples. Below you will find sets of 100% resolution crops captured in uncompressed RAW format using a Sony a7R III. The images were processed in Capture One using the Natural Clarity method with the sharpening amount set to only "30" on a 0-1000 scale (Note that images from most cameras require some level of sharpening but too-high sharpness settings are destructive to image details and hide the deficiencies of a lens). These examples are from the center of the frame.

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Be sure to find details in the plane of sharp focus to base your opinions on. Again, this lens performs impressively wide-open and there is little reason to use a narrower aperture aside from increased depth of field.

Speaking of the plane of sharp focus, this can sometimes move forward or backward as a narrower aperture is selected. Called focus shift (residual spherical aberration or RSA), this issue is seldom (never?) desired and this lens does not exhibit such.

Here is a look at an extreme top left corner.

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Again, we see impressive performance.

Take note that the f/2.8 (T5.6) corner results are not darker than the other aperture results. This lens has a remarkably low amount of peripheral shading and the small amount remains static over the length of the aperture range.

The effect of different colors of the spectrum being magnified differently is referred to as lateral (or transverse) CA (Chromatic Aberration). Lateral CA shows as color fringing along lines of strong contrast running tangential (meridional, right angles to radii) with the mid and especially the periphery of the image circle showing the greatest amount as this is where the greatest difference in the magnification of wavelengths typically exists.

While lateral CA is often easily corrected with software (often in the camera) by radially shifting the colors to coincide, it is better to not have it in the first place. Any color misalignment present can easily be seen in the site's image quality tool, but let's also look at a worst-case example, a 100% crop from the extreme top left corner of a Sony a7R III frame.

There should be only black and white colors in this image and the other colors visible indicate that some minor lateral CA is present.

A relatively common lens aberration is axial (longitudinal, bokeh) CA, which causes non-coinciding focal planes of the various wavelengths of light, or more simply, different colors of light are focused to different depths. Spherical aberration along with spherochromatism, or a change in the amount of spherical aberration with respect to color (looks quite similar to axial chromatic aberration but is hazier) are other common lens aberrations to look for. Axial CA remains at least somewhat persistent when stopping down with the color misalignment effect increasing with defocusing while the spherical aberration color halo shows little size change as the lens is defocused and stopping down one to two stops generally removes this aberration.

In the real world, lens defects do not exist in isolation with spherical aberration and spherochromatism generally found, at least to some degree, along with axial CA. These combine to create a less sharp, hazy-appearing image quality at the widest apertures.

In the examples below, look at the fringing colors in the out of focus specular highlights. The subjects are neutrally-colored, so any other color visible here is being introduced by the lens.

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As illustrated, this lens is not perfect in these regards.

"Sony’s original Nano AR Coating suppresses spurious reflections that can cause flare and ghosting, particularly in backlit situations. The result is consistently high contrast and clarity with deep blacks in the widest possible range of photographic situations." [Sony] Put the sun in the corner of a telephoto lens frame, even one with moderate 14/11 lens element/group count, and flare can be expected. However, exceeding expectations is this lens's flare performance. With a wide-open aperture, only minor flaring effects are seen and even stopped down to f/16, the effects remain mild.

A T5.6 lens is not going to be the first choice for photographing the night sky (at least not without a tracking mount) for most people, but there are two lens aberrations that are particularly evident when shooting images of stars, mainly because bright points of light against a dark background make them easier to see. Coma occurs when light rays from a point of light spread out from that point, instead of being refocused as a point on the sensor. Coma is absent in the center of the frame, gets worse toward the edges/corners, and generally appears as a comet-like or triangular tail of light which can be oriented either away from the center of the frame (external coma), or toward the center of the frame (internal coma). Astigmatism is seen as points of light spreading into a line, either sagittal (radiating from the center of the image) or meridional (tangential, perpendicular to sagittal). Remember that lateral CA is another aberration that becomes apparent in the corners.

The image below is a 100% crop taken from the extreme top-left corner of an a7R III frame.

From a relative standpoint, this is great performance. The stars in the corner remain quite sharp and round.

With one focal length to be designed for, prime lenses usually have a low amount of geometric distortion. While this lens does not have a strong amount of distortion, for a prime lens, I'll call the amount of pincushion distortion it has modest. You might see this distortion if a straight line is positioned along the edge of the frame. It could perhaps be marketed as having a thinning effect on subjects.

The quantity and quality of blur seen in the out of focus portions of an image is referred to as bokeh. Bokeh can sometimes be hard to evaluate, but that is not the case here — bokeh is a standout feature of this lens and some explanation is required.

I'm going to drop a lens design illustration here:

The lavender-colored lens element is aspherical, the green indicates ED glass, and the blue lens element is the APD, an optical apodization element, the key to this lens's outstanding bokeh. As discussed at the beginning of the review, an APD element acts as a radial graduated neutral density filter, allowing a decreasing amount of light to pass through from the center to the periphery.

Let's start with some f/2.8 (T5.6) examples.

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In the "Full f/2.8", we see that the out of focus specular highlights, including those in the extreme corners (the second example), are all round with smooth transitions at the edges. The comparison image is from the optically excellent Sony FE 135mm f/1.8 GM Lens. Without an APD element, this lens has hard edges to the specular highlights and it also has cat's eye-shaped bokeh in the corners.

For a direct comparison, I used an adapted Canon EF 100mm f/2.8L IS USM Macro Lens to represent a normal lens. Before diving into the pixels, I'll share that the camera was tripod-mounted and not moved, yet these two lenses framed the scene slightly differently as illustrated below:

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To better compare the two lenses, the Sony results were cropped to the Canon framing. That this is a "Canon" brand lens used in the comparison is not of big relevance — this lens is representing most normal lenses.

From the image sets captured by the two lenses, two sets of 100% crop comparisons were taken from the upper left region of the frame.

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Here is the second comparison:

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You likely noticed that the f/2.8 (T5.6 on the Sony) results show the greatest difference in quality. As the aperture becomes narrow, less of the APD element's darkened portion is used and the STF lens performs as a normal lens. Here are some f/11 examples.

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These look like the results from most other lenses. The FE 100 STF's aperture ring has an STF line between T5.6 and T8, indicating the range where it provides the greatest effect. Interesting!

Even at f/11, the out of focus highlights remain rounded, thanks in part to a rounded 11-blade aperture. The appearance of the narrow aperture 22-point stars created by this lens from point light sources is decent.

Although this lens is not bright for a 100mm prime, the image quality it provides over the available T-stop range is remarkable with the bokeh being a huge differentiating factor. This is a lens that can create a competitively differentiating look.

Focusing

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The FE 100mm f/2.8 GM OSS lens's AF system utilizes Sony's DDSSM (Direct Drive Super Sonic wave Motor).

This lens internally focuses smoothly, quietly, accurately, and the speed is fast. In AF-S single shot AF mode, the Sony a7R III (along with most/all other current Sony alpha MILC cameras) de-focuses the lens slightly before focusing on the subject even if focusing to the same distance as the lens is already focused to and even with the same motionless subject, resulting in a slightly slower overall focus lock time. In AF-C continuous AF mode, the defocus and focus scenario goes away and this lens's fast AF can be fully enjoyed.

Sony provides an AF hold button on this lens. While in continuous focus mode, this button can be pressed to lock focus at the currently selected focus distance, permitting a focus and recompose technique. This button also acts as a custom button (C5) and can be programmed to another function using the camera's menu (note that not all camera models are supported).

FTM (Full Time Manual) focusing is supported via Sony's DMF (Direct Manual Focus) AF mode.

The manual focus ring is nicely sized and is nice to use. The ring has decent smoothness and the 90° of Linear Response MF rotation is just right for precise manual focusing at all distances. This is a reasonably-well-implemented focus-by-wire design with adjustments being reasonably-smoothly made.

While focus distance marks are not provided, a focus distance meter shows in the lower portion of the electronic viewfinder during manual focusing.

There is a modest change in subject size as full extent focus adjustments are made (without the closer focus distance range being engaged).

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Unique is that this lens provides a focus limiter ring vs. the more common switch and also unique is how it works. Pressing a small button on the left side of the ring releases it to be rotated into one of the two click stop positions, designating a 1.9 - 3.3' (0.60 - 1.01m) or 2.8' (0.85m) - ∞ range. When turned to the shorter range, a group of rear lens elements, including the aperture, shift forward (akin to an extension tube being mounted to the back of the lens).

With a relatively short 22.4" (570mm) minimum focus distance, this lens produces a solid 0.25x maximum magnification.

This is the point where I create a comparison table showing the minimum focus distance and maximum magnification of similar lenses. But, which lenses are similar? The other 100mm lenses have either wide apertures (such as f/1.4) or they are macro lenses which have a distinct advantage in this particular comparison. Only the Canon RF 85 DS has an apodization element, so I'll include that lens here despite it having an f/1.2 max aperture (minus 2 stops for T). I'll also include a couple of other Sony primes.

Model	Min Focus Distance "(mm)		Max Magnification
Canon RF 85mm F1.2 L USM DS Lens	33.5	(850)	0.12x
Sony FE 85mm f/1.4 GM Lens	31.5	(800)	0.12x
Sony FE 100mm f/2.8 STF GM OSS Lens	22.4	(570)	0.25x
Sony FE 135mm f/1.8 GM Lens	27.6	(700)	0.25x

For many more comparisons, review the complete Sony FE 100mm f/2.8 STF GM OSS Lens Specifications using the site's Lens Spec tool.

A subject measuring approximately 5.7 x 3.8" (145 x 97mm) will fill the frame at the minimum focus distance.

Magnification can be increased with the use of extension tubes that shift a lens farther from the camera. Doing so allows the lens to focus at closer distances, though at the expense of long-distance focusing. Sony does not publish extension tube specs nor do they manufacture these items, but third-party Sony extension tubes are available.

This lens is not compatible with Sony teleconverters.

Build Quality & Features

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The G Master series, of which this lens is a member, represents Sony's best-available lenses. These lenses are designed and built for the rigors of professional use.

Members of the same lens family often share design traits and that is what we see here. Here is a closer look at this lens.

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Sony FE lenses have a rather narrow mount and by design, that means a rather abrupt and significant diameter increase starting at just under 1" (25.4mm) into the lens. A small diameter increase occurs at the aperture ring and another small increase tactilely designates the start of the focus ring. The outer lens barrel construction is engineering plastic.

Sony focus rings make distance adjustments by turning in the same direction as Canon lenses (the opposite of Nikon lenses).

Overall, this lens's build quality feels nice with all rings and switches having a precision feel to them. Typical of Sony GM lenses, the AF/MF switch is recessed, making it hard to inadvertently change and requiring a bit more effort to intentionally change, especially with gloves on.

This is a great lens for outdoor use and a dust and moisture-resistant design, including a gasketed mount, can save the day out there. Don't confuse weather sealing with waterproof.

This is a mid-sized lens that is comfortable to hold and use for reasonably long periods of time. Most will not tire of using the FE 100 STF during normal portrait sessions.

Model	Weight oz(g)		Dimensions w/o Hood "(mm)		Filter	Year
Canon RF 85mm F1.2 L USM DS Lens	42.2	(1196)	4.1 x 4.6	(104.1 x 116.8)	82	2019
Sony FE 85mm f/1.4 GM Lens	28.9	(820)	3.5 x 4.2	(89.5 x 107.5)	77	2016
Sony FE 90mm f/2.8 Macro G OSS Lens	21.3	(602)	3.1 x 5.1	(79.0 x 130.5)	62	2015
Sony FE 100mm f/2.8 STF GM OSS Lens	24.7	(700)	3.4 x 4.6	(85.2 x 118.1)	72	2017
Sony FE 135mm f/1.8 GM Lens	33.5	(950)	3.5 x 5.0	(89.5 x 127.0)	82	2019

Again, for many more comparisons, review the complete Sony FE 100mm f/2.8 STF GM OSS Lens Specifications using the site's Lens Spec tool.

Being slightly narrower than some of Sony's other lenses including the 85mm f/1.4 and 135mm f/1.8, the 100 f/2.8 STF does not have as significant of a grip space issue on Sony's current MILC cameras (such as the a7 III, a7R III, and a9).

Use the site's product image comparison tool to visually compare the Sony FE 100mm f/2.8 STF GM OSS Lens to other lenses.

This lens utilizes 72mm filters. This is a common filter size that is not too large, which translates into not too expensive.

The Sony ALC-SH147 Lens Hood is included in the box. This semi-rigid plastic hood does not have a push-button release. The rounded shape means you can stand the lens on that end even with the camera attached (in situations where you are comfortable with that). Nice is that the end of the hood is rubberized, protecting both it and what it is against from scratches and making it less likely to slide. The rubber is also nice to have when bracing the camera against something to steady the shot. And, I think it looks nice.

Sony includes a nice zippered, padded nylon lens case in the box. This case has a belt loop sewn onto the back and a shoulder strap is provided.

Price, Value, Compatibility

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The FE 100mm f/2.8's moderately high price tag is in line with the quality of this product. The price is high enough to give pause to casual photographers but serious and professional photographers will see the value in this purchase.

As an "FE" lens, the Sony FE 100mm f/2.8 STF GM OSS Lens is compatible with all Sony E-mount cameras, including both full frame and APS-C sensor format models. Sony provides a 1-year limited warranty.

The reviewed Sony FE 100mm f/2.8 STF GM OSS Lens was online-retail sourced.

Summary

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The Sony FE 100mm f/2.8 STF GM OSS is a unique lens, primarily due to the optical apodization (APD) element. The APD element causing the physical f/2.8 aperture to transmit T5.6 takes this lens out of the competition for low light action photography applications. However, the APD element does something special with the background blur and this attribute makes the 100 STF especially attractive for portraits and other images with out of focus natural backgrounds.

OSS gives back some low light capabilities (with still subjects) and the image quality from this lens is superb. Add in the qualities that come with GM series designation and the Sony FE 100mm f/2.8 STF GM OSS Lens is a worthy addition to many kits, especially those primarily being utilized for portraiture.