Why Eye AF Is All Anyone Talks About

Why Eye AF Is All Anyone Talks About

So much of the discourse surrounding the latest cameras is usually about Eye AF: how fast it is, how consistent, is camera X’s better than camera Y’s. There’s a reason for that, and it’s not just because it’s the latest buzzword.

Instead, Eye AF represents a couple things. Eye AF is one of the clearest cases of value added by mirrorless cameras. As a software-dependent feature, it’s an opportunity for camera makers to distinguish their product lines without adding anything to the bill of materials. Lastly, and somewhat unfortunately for photographers, it represents the result of other major specs hitting the point of diminishing returns.

A Brief History of Eye AF

Focus tracking, and more specifically subject tracking autofocus is nothing new. DSLR cameras, with their phase-detect autofocus setups, were able to track across a couple of dozen points with decent accuracy. High-level professional bodies, like Nikon’s Dx or Canon’s 1D series cameras could offer something like 50 AF points, spread across the center 1/3 of the frame. Tracking within that zone was actually pretty competent, but as the area was small and the amount of information available to the AF system was limited, it typically wasn’t capable of things like eye or face-aware AF at the same level as mirrorless cameras.

While this illustration isn't technically exact, it should give you a rough idea of the difference between focus point number and coverage between more traditional systems and on-sensor phase detect.

With the advent of mirrorless cameras and on-sensor phase detect, these features got significantly better. Now there were phase-detect points across 90% or more of the frame, and they could number in the hundreds or thousands. Combined with the readout from the sensor itself, it was now feasible to track subjects with much more precision. Eye AF became more consistent, and the availability, or lack thereof, was discussed as a sticking point for buyers.

Face detect AF, and by extension Eye AF, required tight integration between the lens AF performance, image sensor readout and processing, and the software algorithms driving focus. Each of those points has represented an area of potential improvement, and with the last couple of generations of mirrorless cameras, manufacturers have made those improvements.

The Value

At least for me, the autofocus improvements available in mirrorless cameras were a major reason for my switch. Looking beyond Eye AF, moving focus on the chip meant no need to calibrate lenses, as well as no need to focus and recompose. I’d imagine that AF improvements were a significant factor for a number of other users, as AF has served as a major marketing point for most recent mirrorless releases — the latest speed oriented mirrorless cameras have made that even clearer, representing clear competition to the highest levels of DSLRs. For dedicated portrait, wedding, and event photographers, focus and recompose was often no longer necessary. Now it just became a case of selecting the correct eye and firing away.

Eye AF, and the associated improvements aren’t just of value to photographers, though. They also represent significant and meaningful savings to camera makers. Consider the manufacturing complexity involved in a DSLR’s AF: there are multiple mirrors to align, a whole separate sensor module, more complex power, and data routing, all underpinned by a need for tight tolerances between these parts. For a mirrorless camera, basically, all of that can be left off. A mirrorless camera, while it might have a slightly more expensive sensor owing to the inclusion of PDAF points, needs none of those additional parts or tolerance adjustments.

Furthermore, as a feature that is 50% or more software-based, it’s possible to improve every camera in the field with just a few lines of code, delivered via a firmware update. Unfortunately, this can cut the other way, with crippled firmware artificially reducing performance on lower-end bodies, or serving as a way of charging for feature additions after the initial sale (imagine an AF 2.0 upgrade, similar to the raw video output upgrade). Thankfully, that hasn’t yet happened. Instead, firmware updates now actually leave you with a better-performing camera months after release.

The Downside

One unfortunate dimension to this conversation is that we seem to have hit a point of diminishing returns in a number of areas that previously served as banner features. Early on, there was the megapixel race, which mostly died down once cameras hit the 30 to 50-megapixel range. ISO competition has also petered out, with high-performing sensors delivering at least functional 6400 ISO. Dynamic range was a more recent one, but it seems Canon’s latest sensor tech has mostly caught up to Sony’s work, and most cameras now deliver great recovery. Frame rates have risen to the point of being fast enough, with even the resolution-oriented Z7 capable of frame rates that were the domain of sports cameras a few years ago.

One competition that just recently started is the race for a wider aperture. The new mirrorless mounts have enabled even faster lens designs, with things like f/2 zooms and absurd f/.95 primes. With the correspondingly razor-thin depth of field, these lenses demand better than ever AF performance, at least when they can be bothered to include AF in them. To make these designs usable, AF performance has to be great.

As a result, it’s clear that it’s in the manufacturer's interest to focus on autofocus. Not only does improved AF capability represent a carrot for those who haven’t yet switched, it’s also a helpful cost-savings measure in an industry that needs to pinch every penny. Photographers benefit from a better performing system, capable of delivering consistent results under a variety of conditions, and capable of being used with exciting new lens designs.

Things have come a long way from my first experience with live view AF, which was a clunky, contrast-detect experience. Fortunately, this progress doesn’t seem to be slowing down yet, as chip speeds are still improving, and even-faster sensors promise more data for those algorithms to crunch. So, while Eye AF might still be a bit of a buzzword, it represents a feature that actually delivers value to photographers, and shows that new cameras haven’t run out of development opportunities yet.

Lead image courtesy of Amanda Dalbjörn

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29 Comments

Lenzy Ruffin's picture

Camera features have definitely reached the point of diminishing returns for my needs. My Canon 5D3, which I still use, meets all my still photography needs. There's nothing I need it to do that it's not capable of doing.

When I wanted something smaller and more fun to use (because it was easy to take everywhere and didn't intimidate people) and I wanted to get into video, I bought a Fuji XT2.

The XT2 was what I needed at the time, but as my video needs grew, it became deficient. The XT3 fixed all those deficiencies and meets all my photo and video needs. The XT4 doesn't offer anything I need and I suspect the XT5 or XH2 won't either, since I don't need anything that I don't currently have.

One of my pandemic projects is organizing my old photos.

I look at photos of my friends from my college days that I took with a point and shoot film camera, back when I'd never heard the word "aperture" and had no idea what shutter speed was. I see a lot of grainy photos with not great composition or lighting or subject isolation...and they're all priceless. I wouldn't trade them for anything in the world.

And then there's the family photos from before I was born that are even "worse."

Old photos like those are what cured me of GAS. You can't buy a camera or lens in the last ten years that's not a hundred times better than the cameras that produced images that you wouldn't trade anything in the world for.

I am going to get a Fuji XE4, though. Not for new tech, but because it's even smaller than the XT3 and I'll use it more like I used those point and shoot cameras back in the day. And it's perfect as a high-end webcam or for the occasional vlog. No real new tech in it, just a better packaging of existing tech.

Insect eye AF, 200 megapixels, and 75 fps raw with unlimited buffer aren't necessary for any of the things I had in mind when I got into photography. I think a lot of folks get caught up chasing specs and forget what brought them into photography.

Ed C's picture

I agree by and large. There are things that are still useful for me but there is such a wave on nonsense that specs matter more than results it is crazy.

barry cash's picture

Just a great topic for the current times and hits back on all images from past shoots.
Diffraction sets in early with the new breed of cameras after 5.6 its degrading
ISO over base at F1.2 already burns in noise in yeilding non recoverable details .
Wide open fast glass has very thin DOF tolerances as always but now subject or camera moves slightly at wide open apertures no AF system can't handle less than 5mm DOF and get clinically perfect focus.

BUT, I believe the newer AF systems will yield better results then those of past and therefore a reason to upgrade if you're shooting Kids, Sports, Animals or erratic moving subject. How they really stand up will most certainly be determined by new micro motors in the lens also requiring us to buy new glass. This change will globally affect older system kits.

David T's picture

I am lazy. I love the convenience and reliability of Eye AF.

The days of 5D2 were dreadful when every point except the middle one was almost unusuable. Back button focus and recomposing a thousand times during a metal concert probably gave me arthritis or something.

It's like GPS. If the point is just getting from A to B as reliable as possible, I will use GPS any time. Using a paper map is a fun exercise that I would indulge in when hiking or something.

AJ L's picture

People pay too much attention to the camera’s ability to draw a yellow box over an eye. They see a YouTube video of a model spinning in circles while the camera puts a yellow box over her eye, and buy that camera, ignoring everything else (including the fact that all the cameras these days are getting a a good percentage of actual focused shots, regardless of whether the camera has the yellow box).

David T's picture

People are too quick to dismiss buying decisions.

If I spend money, why wouldn't I want the camera with most focused shots? Why wouldn't I want the most reliable car? Headphones with best sound? A screen with accurate colors?

"Good" percentage (how much is good? 60%? 70%?) isn't good enough when I spend my hard earned cash. I am not a charity.

AJ L's picture

Well, if you bought the camera that has the best yellow box, you’d find that the yellow box doesn’t actually guarantee you a focused eye and you’re missing up to 30% of the time you thought you had it when the subject is moving. Oops. The yellow box isn’t everything.

David T's picture

OK, so your issue is with testing methodology not Eye AF? Fair point, although reviewers usually state or provide the series of photos so you can see how many photos are actually in focus.

AJ L's picture

I also think that since none of these systems are perfect and all work fairly well once you’ve got some practice, competing eye AF isn’t such a big deal and most people would benefit from making other comparisons.

David T's picture

I tested Fuji X-T4 vs A7iii and it was atrocious. Face AF mistook random objects or body parts for faces, was super slow and unreliable. Maybe a hit rate of 80% vs like 98% on Sony. What Fuji does better is Face Select button.

Panasonic has tap-to-select-face which is the best system. But the overall performance is worse than Sony. Still feels reliable.

So yes I agree that Eye AF just needs to reach a level of "can rely blindly on it", but that is what some current cameras still manage to fail.

Tom Reichner's picture

David T said,

"So yes I agree that Eye AF just needs to reach a level of "can rely blindly on it", but that is what some current cameras still manage to fail."

I am with you 100% on this.

I look forward to the day when I can have a camera that will focus on my subject's eye whenever I want it to ...... no matter how little light there is, no matter how far away the subject is, no matter how small in the frame the subject appears, and no matter how rapidly and erratically the subject is moving.

If a duck is flying 300 feet away from me, then I want to aim the camera at that duck and have the camera pick out the duck's nearest eye and lock focus on it in a millisecond, and then keep that eye in precise focus the entire time I have the duck in the frame.

Anything less than this is not good enough, and I look forward to the day when technology makes this possible on a 100% consistent basis.

I want to use all of my energy positioning myself, anticipating subject behavior, timing the shot, assessing the background, and composing the image ..... and let the camera do the focusing so that my eyes and brain and fingers are free to do all of that other super-important stuff.

Tom Reichner's picture

AJ L,

You are creating a straw man.

No one - I mean no human on earth - has bought a camera because of the yellow box representing a focus point. People buy said camera because the camera is actually making the lens focus on the subject's eye on a consistent basis, not because the manufacturer uses a yellow box to show the active AF point.

People are basing their purchase decisions on actual focus performance, not on the presence of the yellow box.

Eric Bowles's picture

Actually, people buy cameras for a lot of reasons and then are surprised when they can't execute the shot they wanted. The yellow box problem is just one issue. I'm sure Eye AF will mature. But right now you don't really know whether any of these AF methods will yield 20% in focus or 90% - even if the box indicates focus was achieved. What's more, your miss is not predictable.

Eye AF, Face AF, and Animal Eye AF are tools. In skilled hands they do pretty well. For photographers that don't look through the viewfinder and shoot loose compositions, they work well. But for someone who already is getting 80-90% of their shots sharp and in focus, they are at best an opportunity to try different styles of shooting if critical focus is not required.

AJ L's picture

I think you’d be surprised how many people have it in their head that only one brand of cameras can focus, because of a certain long haired guy’s videos of yellow boxes. If people obsessing on Facebook are an indicator, there are a lot of sales being driven by that.

Marcelo Rojas's picture

I think the reality is we are hitting peak Digital Camera. Camera manufacturers have no interest in actual smart tech and computational photography and solely rely on sensors and lenses. (Which currently for the past 11 years, has not been working out so good).

Camera manufacturers moved to Mirrorless to compete with smartphones but reality is (debatably) lighter bodies (sometimes, if at all) and newer lens mounts can’t fix the problem. People want one device and one device only.

If smart phones had an instant print feature the entire camera industry outside of advertising is dead. Camera sales will never recover and 100 year old brands will die out. Especially those who are late and can’t even get Eye AF right (Nikon).

It’s a make or break situation for a lot of people and tbh the (normal consumer) camera industry only needs 3 brands.
Canon
Sony
FujiFilm

It’s time for companies to go bankrupt and to be merged with either of these 3.

High end will always remain Leica and newly Phase One (Hi Mamiya).

Marcelo Rojas's picture

We are at a point where Mega Pixels don’t matter and are just a creative tool for crops.

Shutter speed hasn’t mattered since 1940

ISO is the best it’s ever going to get and will only see maybe if at all 5% year on year improvements. For the past almost 20 years 1600 iso - 3200 is still the standard Sweet spot for almost all cameras without dual gain sensors

Frames per second for photos is seeing an interesting increase. There has been 0 advancement here for over 60 years (since winders were invented) and 10fps -20fps Max has been common for over 6 decades.

Autofocus has reached peak auto focus

And the only meaningful advancement in camera tech in the past decade has been video. So realistically at this point what else can be added? Dual gain sensors as standard? IBIS? Which is already reaching peak IBIS. There is not a whole lot left to add or many places left to go besides maybe computational HDR and focus stacking.

But even if that’s added then what? That’s it for Digital. A new medium will have to take its place

Marcelo Rojas's picture

Ask yourself this.
Now that the:
100MP
1/32000th
409600 ISO
Bird eye from 7 million mile away Eye AF
8K
30fps (photos)
9 stop IBIS

Barriers have been reached what’s next? It’s only Global shutter and some computational photography to increase dynamic range. We are not just peak digital we are peak camera

Heiko Knoll's picture

. . how about in-camera sky replacement? :-))

Teemu Paukamainen's picture

Now don't go giving the camera makers such ideas!!! :O

Marcelo Rojas's picture

It turns out even with all this:
100MP
1/32000th
409600 ISO
Bird eye from 7 million mile away Eye AF
8K
30fps (photos)
Dual gain sensor
9 stop IBIS
14+ stop dynamic range

Most people only wanted 1 thing.
12 MP and convenience.
That’s why the camera industry is dying -
(in comparison to industry peak).

We are reaching peak Camera and it turns out all most people want is either an instant shareable photo or an instant print. And really what else matters?

David T's picture

Reliable Eye AF is part of convenience to me. But yeah software features are very lacking. They need an open API or something - tether the camera to the phone and let phone app developers figure out all the nice stuff.

Tom Reichner's picture

I don't know of any serious photographers who want "instant sharable" or "instant prints". And I know of very few serious photographers who care about "convenience", if by convenience you mean small size and light weight.

Almost all of the serious photographers I know - several hundred of them - use big lenses for 90% of their work; lenses like 600mm f4, 500mm f4, 300-800mm f5.6, 200-400mm f4, etc. They aren't looking for camera bodies that are smaller or lighter; they couldn't care less about that.

The serious photographers that I know also put a lot of value on editing their images very carefully. They spend many hours every week in Photoshop and Lightroom, making each image as perfect as possible before they will ever even consider sharing it. So we can't relate to what you say about photographers wanting "instant share" and "instant print". That just isn't true for the hundreds of fine art wildlife photographers that I know, nor for the many thousands of other fine art wildlife and nature photographers that are out there.

Linden S's picture

Sheesh! As a Sony mirrorless shooter I really wanted to read this article but the ads that keep on blocking BOTH SIDES OF MY PHONE’S SCREEN and covering essentially 20% of the actual content made it incredibly annoying and almost impossible so I just scrolled to the bottom and fought the ads to say this. Repeats every 12 seconds or so, and stays there for about 5 seconds, and changes the scrolling/clicking behavior while it’s active. I’m all for you guys making money with ads, but this is ridiculous!

terry pitcher's picture

Same here. The swarms of ads make fstoppers unusable.

terry pitcher's picture

Creativity aside, from the pure tech point of view, I think that eye AF is a tectonic shift. It's the first time ever when the technology raises to the next level of abstraction and instead of just measuring contrast at a certain point gains an "understanding" of the subject. Now it "knows" what is person and what is eye and that the photographer is interested in keeping that eye in focus.

Again, personally I still prefer low-tech. I love shooting with my Leica M and I prefer it to any smart tech that takes the craft and decision making away from me. But, at the same time, I can't help to admit and admire the technical progress and human effort behind it.

Muhammad Asif's picture

Superb

Hans J. Nielsen's picture

Good article. Think it hit the truth right in the eye.

jim hughes's picture

We're all getting desperate for something in a photo that impresses people and let's us say "see that? You couldn't get that with a phone." Not sure I want to "rejoin society" :-)

Joe Hoddinott's picture

Next up: computational photography.