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News & Insight

The Bokeh In The Beast: Sony’s STF Bokeh Mastery Explained

By Wendell Weithers on February 20th 2017

When Sony introduced their new G-Master lenses, they designed them to produce the highest resolution and pleasing bokeh. For anyone unfamiliar with “bokeh”, that’s not a word from the latest Minion movie; its the Japanese word referring to the visual quality of the blur in the out of focus area in your images. While stunning bokeh is a key feature in the other lenses in the G-Master lineup; it is the focus, if not the primary purpose of the 100mm 2.8 STF lens. STF stands for Smooth Trans Focus, and if you are wondering how it make this lens stand apart every other new lens on the market, here is breakdown of what it means.

[REWIND: Sony Unveils 2 Mid-Telephoto Primes & A New Flash | FE 100mm 2.8 SFT GM, 85mm 1.8]

So… how does this work?

Sony included an Optical Apodization Element which acts as an in lens graduated neutral density filter that transmits the most light at the center  and then gradually decreases towards the edges of the element.

The impact of this element creates an extraordinary smoothness to the bokeh in your images, avoiding both the distorted shape and harsh edges you may find in other lenses.

[REWIND: Hands On With Sony’s Newest Gear | 100mm 2.8 STF GM, FE 85mm 1.8, & New Flash]

There is a high level of thoughtfulness in this design and presents yet another example of Sony setting their products apart from their competition. Futhermore, the 100m focal length and the specialization in the design gives this lens the opportunity to go unchallenged and develop a cult following from photographers. At a price just shy of $1,500, this bokeh ain’t cheap and while it is slower than Nikon’s 105mm f1.4, it is $700 dollars less expensive. Ultimately, this seem like a lens worthy of the G-Master label that will be alluring portait photographers for years to come.

The Sony FE 100mm f/2.8 STF GM is slated to be available at the end of March. You can preorder your copy here.

Wendell is based in Atlanta where he shoots events, portraits, and food photography. He also supports his wife Andrea as she runs their cake design business, Sweet Details.

Instagram: Wendellwphoto

Q&A Discussions

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  1. Black Z Eddie

    So, because of the TStop of 5.6 at f2.8, how is this lens at lower light.  Let’s say, an ISO 3200 or even 6400.  Would it be overly grainy.  Some of the sample footage on their commercial appears to be at low light so I’m guessing it’s probably a non-issue?

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    • Patrick Chase

      From a noise perspective it would be exactly like shooting any other T/5.6 lens in those light conditions. The apodization filter won’t have any impact on shot noise or read noise, after all.

      You can’t judge anything about absolute light intensity from the commercial, as It’s the easiest thing in the world to make a brightly lit scene appear to be “low light” by manipulating constrast and shadows. Hollywood films do it all the time.

      I would not use this or any other T5.6 lens for low-light work, FWIW

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  2. Spencer Pablo

    I like how the subjects do not compete with the bokeh anymore. Sometimes the bokeh ends up being a distraction with some of the other glass.

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  3. Adam Palmer

    I wonder why they always do this to 2.8/2.0 lenses.  I’d like to see it applied to a 84mm 1.4

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    • Stan Rogers

      The biggest single reason is that it can only work over a very small range of apertures (about a stop, maybe a stop and a third, end-to-end before apodization basically stops happening in any meaningful sense). So your 85/1.4 would be an 85/1.4-2.0 as an apodized lens and a mostly-ordinary lens stopped down any further, but with a very high light transmission penalty. The lens is already a one trick pony (although it’s a really, really good trick that it does very, very well); making it a one trick pony with no DoF to speak of would restrict its use cases too much to sell at a reasonable price (where “reasonable price” is something a pro would be willing to pay for a tool).

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    • Patrick Chase

      Stan Rogers To be fair, the transmission penalty also decreases as you stop down. If the apodization filter is 100% transmissive in its center then the penalty should approach zero at very small apertures (like f/22). 

      Also the depth-of-field will be a bit larger for an STF lens than for a conventional lens of the same aperture. The reason this is true is because the blur point spread function of the STF lens is “peakier”, which means that it will degrade MTF less than would a conventional blur disc at any given blur diameter. As a completely guesstimated example, a 30 um STF blur might have ~50% higher MTF50 than a 30 um conventional blur disc. 

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    • Stan Rogers

      Its not likely to be 100% (well, as close to 100% as a lens element gets, anyway), since it’s a couplet and the dark element needs to have  non-zero thickness. You do get a little better DoF even wide open, but not enough to cover typical use cases with an f/1.4 short tele (couples, half-length portraits, mother-and-child, that sort of thing). Again, think of it as a tool to get a repeatable effect rather than as a neat experiment, and the sorts of photos that are likely to make the tool pay for itself.

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  4. Alex Kartashov

    That’s.. actually pretty impressive. 

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  5. James Ogden

    Interesting. I’m not sure if I like that type of bokeh, it looks off to me.

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    • Jean-Francois Perreault

      I can only base my opinion on the samples above but to me it looks much more natural and much less distracting.

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    • Kishore Sawh

      Hi James, I spent some time with the lens about a week or so ago and I can tell you, from my experience, if you’re not used to it it can throw you at first, but the kicker is that going back to anything else really stands out as distracting. I’m not a bokeh-crazed shooter or viewer, but this is impressive and more pleasing as time goes by. 

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    • Wendell Weithers

      I was put off at first, but it is a unique look. I figure it would grow on me, it already has..:)

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    • Ben Perrin

      Yeah, I prefer the standard bokeh when it is rounded. But having said that if people prefer this kind of look then it’s good that they’ve got the option.

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