Sony FE 100mm F/2.8 STF Real world images (click for larger):
Sony FE 100mm F/2.8 STF lens review:
The Sony 100mm F2.8 STF lens is almost entirely unique to Sony. STF stands for smooth transition focus. Innovative design allows this lens to render background blur in a much smoother fashion than “normal” lenses. Minolta first released a 135mm STF lens for their SLRs. Sony took over the Minolta A-mount and re-badged the same lens for the Sony A-mount system. I know many Sony A-mount shooters who prized this lens as a unique benefit of the Sony A-mount system. There are now some third party manual focus STF lenses for Canon and Nikon, but they do not have a native lens with this same design and technology. Unsurprisingly, it was just a matter of time before Sony released a STF lens for the mirrorless system. The Sony FE 100mm F/2.8 STF lens is the only STF lens that has autofocus.
My review of the Sony 100mm F/2.8 STF will be a bit different than my other reviews. I’ll cover the basic of image quality, etc. But such discussion is almost superfluous, the bigger question is whether one would want the Sony 100mm STF lens over “normal” prime lenses of similar focal length.
Body and Handling:
Build quality is excellent, in line with Sony’s other premium lenses.
First thing you will notice, while the lens model proclaims to be F2.8, the aperture ring starts at 5.6. Where is the 2.8?!?!?!?! This is the technology of STF. Aperture, technically the size of the lens opening, affects the amount of light entering the camera and it affects the depth of field. The STF lens design causes a separation of these two effects. At maximum aperture, the STF creates the background blur equivalent of F2.8 but only allows light gathering of 5.6. The lens aperture ring is technically listing the T-stops — Light transmission.
Instead of a focus limiter switch, the Sony 100mm STF has a focus limiter ring at the base of the body. It can be set for macro-ish close focus or for distant focus. Unlike most focus limiters, it cannot be set for the full focus range. You must choose near or far. As noted above, this is the only autofocus STF lens that I’m aware of. Apparently, autofocus is difficult with these lenses which may be part of the reason the focus limiter is designed in this fashion. (Pure speculation on my part)
Switches on the side of the barrel allow for manual focus/autofocus and for “clickless” aperture, allowing video shooters to change aperture in silence. There is a focus hold button, very useful when re-programmed for eye-AF. Especially at this is a lens built for portraits.
At 700 grams, it’s a fairly hefty lens. Personally, I feel it starts to push the limit of what’s truly comfortable for long periods on the Sony A7riii. Pushes the limit but doesn’t break the limit. The balance is fine, and I’d be comfortable hand holding the lens for long durations. Still, be aware that it certainly is not a feather weight lens.
There is a massive hood included with the Sony 100mm F/2.8 STF. The size of the hood suggests to me that Sony was aware that flare could be an issue for this lens.
Autofocus can only be described as fair. Perhaps because the light gathering is only 5.6, autofocus was not as consistently fast and snappy as other lenses. That said, I didn’t experience significant hunting. Focus was entirely silent. Certainly completely adequate for any real world use of an STF lens.
Image Quality
By regular measures of image quality, the Sony 100mm F/2.8 STF delivers. Nobody is going to complain about the sharpness of this lens or most other technical image quality characteristics. Of important note, it’s difficult to compare the technical quality of the lens to other lenses. While most other primes in the focal length range would have a maximum aperture of between 1.4 and 2.8, the maximum T-stop of the Sony 100mm STF lens is a rather slow 5.6. It simply doesn’t let in nearly as much light as other primes. Every Sony lens has fantastic image quality at F5.6, thus I can only give the Sony 100mm STF lens so much credit for having excellent image quality wide open — At T5.6.
Vignetting
Simply put, vignetting is not an issue. There is very minor vignette at T5.6 (F2.8) and it’s completely gone at T8. The minimal vignette won’ detract from wide open images, considering the general purpose of this lens to create nice background separation.
Flare – Chromatic Aberration/Purple Fringing –
These horribly back lit photos will emphasize any purple fringing issues. Purple fringing tends to affect wide apertures. It’s not a big issue with the 100mm STF. Where the sun pokes through the branches the strongest, we do see a bit of purple, but it doesn’t affect most of the frame.
Flare is THE technical weakness of the Sony 100mm F/2.8 STF lens. You will note pretty significant flare and ghosting at all apertures. Not something easy to correct in post-processing. These samples were taken with the large hood in place, which still couldn’t prevent flaring. It’s no wonder the hood is included as flare would be even more of an issue without it. Unless you like the flared look, avoid getting strong light into the frame.
Sharpness
Normally, this is my most detailed section of any review. For this review of the Sony 100mm F/2.8 STF, there isn’t much point pixel peeping sharpness. As noted, wide open, the lens gives a T-stop of 5.6 and F-stop of 2.8. Thus, this lens would be nearly worthless if you had to stop down even further to get sharp images.
So let’s look at some crops to see if the Sony 100mm F/2.8 passes or fails:
It passes the sharpness test. The far corner is especially impressive, nearly as sharp as the center, just a tad of softness. Stopping down to T8, the corner sharpens up a bit more:
Ultimately, this is probably one of the sharpest lenses I’ve tested for Sony. On one hand, all of Sony’s lenses are incredibly sharp at F5.6, so it’s not much of an advantage of the Sony 100mm F/2.8 STF. On the other hand, when those other lenses are at F5.6, you are getting far less background blur. The Sony 100mm f/2.8 thus allows you to get that amazing level of sharpness while getting background blur equivalent of 2.8.
Bokeh and Image Comparisons
The real question is simply whether you like the unique look of the Sony 100mm F/2.8 STF. STF stands for “smooth transition focus.” It renders the background blur much more smoothly, bokeh balls become less prominent. In showing images to non-photographers, there was a split in opinion as to image preference. The “smooth transition” look isn’t for everyone.
For these comparisons, I used the Sony 85mm F/1.8 as well as the Sony 90mm F/2.8 Macro, as these lenses are closest in focal length. As shown above, the Sony 90mm F/2.8 macro is actually a bit longer than the Sony 100mm F/2.8 STF, despite being 10mm shorter in focal length.
Let’s start with these 3 images, the first with the Sony 100mm f/2.8 STF wide open. The other two images are from the Sony 85mm F/1.8 at 1.8 and 2.8. Click for larger. Pay attention to the degree and quality of the background blur, as well as the bokeh balls.
In terms of purely the amount of background blur, the 85mm lens gives the narrowest depth of field when wide open at 1.8. The degree of background blur is nearly identical between the 100mm STF at T5.6 and the 85mm at 2.8, but the bokeh balls are rendered very differently. Let’s crop just the bokeh balls in the background from the images:
What a huge difference, though which is best is really a subjective question. The 85mm lens gives bokeh balls with clear edges. With the Sony 100mm f/2.8 STF, you get the same degree of blur (as the 85mm at 2.8), but the bokeh does not have clearly defined edges at all, just soft roundish highlights. It’s hard to grade this bokeh as anything other than “different” or “non-traditional.” I think some viewers of photography expect and prefer to see obvious bokeh, some may never even notice the difference, while others will prefer this smoother softer look.
Wide open, the Sony 100mm F/2.8 STF just doesn’t readily create identifiable bokeh balls:
Notice again, the well rounded and obvious bokeh in the image taken with the 85mm lens at 2.8, while the Sony 100mm f/2.8 just gives a very smooth creamy blur.
Which do you prefer? There is no right or wrong answer. The Sony 85mm f/1.8 obviously gives the most blur in the background, but it is a bit busy. Closest to the STF lens in aperture and focal length, the Sony 90mm F/2.8 macro lens gives the same degree of background blur but it is very very busy in comparison. Personally, I prefer the look of the Sony 100mm STF f/2.8 compared to the other two lenses at 2.8, but part of me prefers the look of 85mm at 1.8.
Looking at a closer portrait example:
By moving closer to the subject, we get very narrow depth of field with all of the lenses. Even with an F stop of 2.8, you get very narrow depth of field, completely blurring the background, in all of the images. Personally, I don’t see tremendous differences in rendering in these examples, where the background is so thoroughly blurred by every lens. Further, in terms of portrait sharpness, all of the lenses are plenty sharp enough.
Portraits are certainly the main use of the Sony 100mm f/2.8 STF, but let’s look at a non-portrait comparison:
The bokeh differences are especially apparent in these three images. Even when there is the same degree of background blur, I almost feel like I get more depth of field from the STF lens. In fact, an experienced portrait photographer was looking at some portraits I did with the STF lens, and commented that I really should have opened the lens up to 2.8 to get narrower depth of field. (The Exif data showed the T-stop of 5.6). The type of background blur is just very different than what people expect in narrow DOF cases.
Overall
This is a unique lens and there really isn’t any substitute. Priced at $1,499, it matches other premium primes. Except for flare, there really are no technical flaws with the Sony 100mm f/2.8 STF.
But I ask myself, is the Sony 100mm f/2.8 STF too much of a 1-trick pony? With a maximum T-stop of 5.6, the Sony 100mm F/2.8 is nearly useless for low light. For wide depth of field shooting, there would be no advantage to using the Sony 100mm f/2.8 STF lens over any other lens of similar focal length. A lens like the Sony FE 85mm f/1.8 (review here) or the Sony 85mm f/1.4 GM will produce images of equivalent image quality, with the potential for more blurred background and far better low light capability. The Sony 90mm F/2.8 macro will give you the same sharpness, the same degree of background blur, better low light capability and true 1:1 macro function.
The Sony 100mm f/2.8 STF is primarily for shooting outdoor portraits where you want pleasant background blur. That’s where is excels over other lenses but many might actually prefer the blur rendering of traditional prime lenses.
If you like the look of the extremely smooth background blur, the Sony 100mm F/2.8 will deliver. But if you’re more equivocal, you are probably better off sticking to traditional lenses. If I had an unlimited budget, I’d probably keep this lens myself but in prioritizing, this is simply a lens that isn’t personally worth the cost for me.
Rating (1-10): Score: Unscored, too unique
(About my scoring: 9-10 is a superb lens which could have a place in the bag of almost every photographer. 6-8: recommended with caveats. 3-5: A compromised lens that may still be suitable for some shooters and situations. 1-2: Just stick to your phone camera)
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