Autofocus speed and accuracy

The Fujifilm X-T10 benefits from the company's latest autofocus system, which Fujifilm has also made available to X-T1 users via its recent autofocus firmware update. This new system is said to offer improvements to AF speed and precision, especially when shooting low contrast subjects. This increased precision was achieved by analyzing smaller portions of the AF point. The new system also adds two new AF modes, Zone and Wide/Tracking.

The X-T10's AF system comprises 77 contrast detect and 15 phase detect points. The phase detect points, which are sensitive down to EV 0.5, are arranged in a 5x3 array in the center of the frame, the contrast detect points fill the rest of the frame.

Users can select the entire 5x3 phase detect point array, or a 3x3 chunk of it, by using the new Zone AF mode. It's worth noting that when shooing in continuous AF, the Zone AF mode will only allow users to select a zone in the phase detect portion of the frame. However, when shooting in single AF, the zone can be placed anywhere in the frame, even outside of the phase detect area. Users can also select up to a 5x5 array when shooting in AF-S.

The X-T10 also features a new Wide/Tracking AF mode; it employs all of the AF points, phase detect and contrast detect, across the entire frame. We were told by Fujifilm's engineers that the tracking functionality works best with moving subjects against a stationary background, which limits its practical utility: we don't know about you, but we don't typically shoot moving subjects on a stationary tripod.

Autofocus works best when shooting in AF-S. For this image, I first acquired focused on the net and held the shutter halfway to keep focus, while I recomposed and waited for the right moment to shoot a frame. ISO 400, 1/500 sec, F14.

Before continuing, it is worth mentioning that Fujifilm's ability to track subjects across the frame lags significantly behind many of its competitors, with Nikon, Sony, Panasonic, Samsung, and Olympus offering far more mature implementations. Fujifilm's face detect and eye detect functionality, particularly in continuous AF, also lags behind better implementations found in competitors. In fact, when it comes to continuous AF, it's really only single point AF-continuous in the central portion of the frame that Fujifilm excels at, and you'll be better served by more advanced subject tracking in competitors if that's something you're looking for. Still, AF-single is perfectly capable and accurate to boot, and it is refreshing to see the company addressing the obvious desire for more advanced subject tracking capabilities. We hope this is an area they will continually improve as the company iterates.

General autofocus speed and accuracy

In general, when the X-T10 acquires focus, it does so accurately. Still, the camera does get confused when you try to acquire AF on a subject that falls into the infinity end of the focus scale. This is especially true of very bright subjects, like a setting sun in the distance. In these scenarios, it is not unusual for the camera to miss focus or simply be unable to acquire focus at all.

We mentioned this in the shooting experience, but it is also worth noting here that when shooting in AF-S, the X-T10 will very rapidly hunt past the subject before acquiring focus. You'll see this as some significant 'fluttering,' right before the green square appears indicating focus has been achieved. It's ways less noticeable when shooting with one of the kit lenses, and more noticeable when shooting with primes, or zooms. We were expecting a bit less of this given the phase detection points on the sensor, but the Fujifilm likely continues to use a good deal of contrast detection for final AF confirmation. This is why your see the 'fluttering.' Despite this, AF is still very quick, especially in good light.

Low light and low contrast AF performance

The speed and accuracy of AF acquisition on low contrast subjects has been improved over previous Fujifilm cameras. The above image, which is a JPEG pulled from the camera, was shot using face detect in AF-S, with the focus mode set to Wide/Tracking. In most cases, not only was the X-T10 able to identify the subject's face, but it was also able to lock focus, in a reasonable amount of time, despite the very dim lighting and lack of contrast. ISO 6400, F4, 1/15 sec.

The X-T10 does an acceptable job of focusing in low light. Does it do better than the X-T1 before the firmware update? Yes, thanks to the increased sensitivity of the phase detect points from EV 2.5 to EV 0.5. By the way, these numbers are quoted, to our knowledge, for F2.8 lenses; you'll get better results with faster lenses and worse results with slower lenses on these mirrorless systems.

AF speed and accuracy when shooting a low contrast subject has also been noticeably improved from previous Fujifilm cameras. In the vast majority of dark, low contrast scenarios I tried to the X-T10 in, it was able to accurately achieve focus. But while the improvements are real, performance still is not perfect. The camera may rarely flat out miss focus on a low contrast subject, but AF Acquisition can be painfully slow, depending on how low contrast the subject in, and which lens is affixed.

It is also worth mentioning that the X-T10 still lags a bit behind the competition in terms of PDAF sensitivity compared to other APS-C cameras near its price range. In our head-to-head tests with F1.4 lenses across all systems, the a6000 continues to phase detect AF in lower light than the X-T10, as does the Nikon D5500, with all its AF points capable of focusing even in continuous down to EV -1.*

Continuous Autofocus

The X-T10 is capable of continuous autofocus during high speed shooting (up to 8fps). As should be expected, keeping your subject in the central portion of the frame, where the phase detect points are, helps greatly in keeping focus on a subject moving toward or away from the camera.

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However, when shooting an 8fps high speed burst, the X-T10 is limited to just eight frames, regardless of whether you are shooting Raw files, JPEGs or both. In the roll-over above, the first eight images were shot during the burst, the remaining seven were shot at a slowed down burst rate closer to 3fps. Still, we were fairly impressed with the results. The camera did a good job of keeping the cyclist sharp and in focus. Of the eight frames in the high speed burst, seven of them are in focus (or are very close to it).

Fujifilm may not be the first camera company that comes to mind when considering a brand that can shoot sports or fast action. But the X-T10 certainly appears to keep up against the competition, at least when using a single selected AF point in the central phase-detect area of the frame. The first example in the video below, this time shot at a wider focal length, mimics the findings of our bike test above, with the X-T10 able to keep the mannequin head in focus as we move the camera along the Z axis.

Face Detection and Eye AF

The above video was shot with the 18-55mm F2.8-4 lens attached. In general, we found this lens gave us better AF performance than many of Fujifilm's primes, which suffer from slower focus motors. The final clip in the video shows the X-T10's performance when using Face Detect in AF-C, while shooting a burst at 3fps (CL). The frames captured can viewed at 100% in the roll-over below.

Face Detect is implemented in a bit of a confusing way in Fujifilm cameras. While it might seem natural to think of Face Detection as an add-on feature, something you flip on while shooting to give yourself a leg up on locking focus on human beings, it actually overrides all other AF functionalities. For instance, when Face Detect is turned on, the ability to use AF-L is disabled when shooting in AF-S. You also can not change the Photometry (metering) settings. Furthermore, the X-T10 appears to turn off PDAF and use contrast detect AF only when Face Detect is activated.

The X-T10 also doesn't appear to honor your chosen AF area: even if a face is detected outside of your selected point or zone, the camera will focus on it. This can be a good or bad thing depending on your style and preference. It also means that you can't choose a preferred face on-the-fly by placing it over your selected AF point and then having the camera track it (as you can with eye AF on the recent Sony RX100 IV); rather, the camera makes up its own mind as to which face to focus on.

Since the camera will focus on any face in the scene when face detect is on, it doesn't matter what AF area you've selected. If a face isn't detected, though, the camera will just revert to whichever AF area mode you've selected. It's also worth pointing out that face detect is very laggy when the camera is set to AF-C, too laggy to be useful in many cases, and especially with some slower-to-focus lenses. Continuous AF engages focus 'wobbling', or back-and-forth hunting, so lenses with slower focus motors (like a number of Fujifilm's primes) really slow down continuous AF with face detect.

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As the above video demonstrates at 0:27 mark, the X-T10 has no issue staying with a moving subject (face), or in the case of the video, a static subject with a moving camera, as long as the shutter is not half pressed. The second you hold the shutter, everything grinds to a halt, and tracking becomes incredibly laggy. You can see this in the video above as the green box outlining the face goes from swiftly following the face to barely being able to keep up, jumping every now and then to catch up to the movement.

If you try to hit the shutter in AF-C, with Face Detect on, there is a 1 to 3 second delay before the frame is captured as the camera waits for focus to catch up. Performance varies a bit based on the lens you're using, with slower focus lenses like the 16mm F1.4 leading to more of a lag than faster focus lenses like the kit zoom (compare 0:44 in the 16mm video below to 0:51 in the 18-55mm video above).

Face Detect works well when shooting in AF-S, which is good for a stationary subject, but not so good for a moving subject. In the case of Doc, shown above, it worked just fine. ISO 1600, F2.2, 1/40 sec.

AF-S results in much better acquisition speed and accuracy when using Face Detect, with a delay of only about .5-1 sec from the time the shutter is pressed, to AF acquisition and shutter actually firing. Still, if your subject is moving, by the time you have acquired focus, there is a chance that the subject will have moved out of it before the shutter fires. In other words, focusing on moving faces with the X-T10 is a frustrating experience.

Users can easily toggle Face Detect on and off as a setting in the Quick Menu, instead of having to hunt through the main menu to find it. It is not located in the Quick Menu by default, but can be added-in manually. It's also worth noting, as we mentioned above, that users do have the ability to toggle their AF point when shooting with Face Detect on, which wasn't always the case with Fujifilm cameras. However, again, if a face is detected, the camera will ignore your selected AF point entirely.

Eye AF can be turned on in conjunction with Face Detect, but not on its own. Users can set it to bias toward focusing on the left eye, right eye, or both/either. Unfortunately, it doesn't really do anything, unless your subject is VERY close. Like Face Detect, it works most effectively with the camera set to AF-S than AF-C.

Subject tracking across the frame

We also tested the X-T10's AF performed when we affixed a high-end prime to the camera, in this case we used the 16mm F1.4. The result was a drop in overall AF speed, when compared to the kit lens. Fujifilm's primes tend to suffer from slower focus motors, which severely slows down continuous AF.

The X-T10 is the first Fujifilm camera to ship with the ability to subject track across the frame, baked in, right out of box (the X-T1 can also do it of course, with the latest firmware). Again, this is brand new territory for Fujifilm as a camera company. Both Nikon (with its 3D AF tracking) and Sony (so-called '4D' AF in the a6000) have impressed us with what their cameras are able to accomplish in terms of accurate subject tracking.

The X-T10 unfortunately can not compete with either. Judging by the results of our our studio testing, (see the above video at the 1:03 mark) and field testing, the focus tracking capabilities are simply too slow and too erratic. Still, we tip our hat to Fujifilm for jumping into the subject tracking game, and look forward to the company potentially becoming more of a contender in this area, down the road. But for now, if you want a camera that can subject track really well, you should look to another brand.

The Fujifilm's guidelines do give an indication that the Wide/Tracking AF mode can be used in one of two ways: to (1) photograph a static, preferably wide scene, with a single moving subject that the camera attempts to track as it moves through the scene, and (2) stay with a subject that has started in the center of the frame, as they move, and the camera moves with them.

The X-T10 does neither of these tasks particularly successfully, though it is worth mentioning that we had better results, in both instances, shooting with the 18-55mm F2.8-4 kit lens (demonstrated in the first video), than we did with the high-end 16mm F1.4 prime. This is likely because the kit lens' AF motor can physically hunt faster, giving it a leg up in terms of AF speed. Furthermore, if you use this mode, you'll want to start with your subject in the center as results are better this way (perhaps it helps the system to start with depth information about the subject using the central phase-detect points).

What's it all mean?

X-T10 AF performance in a nutshell? AF-S (single) is quite good and accurate, as we expect these days from mirrorless cameras. Face detect in AF-S also works, though you unfortunately don't have a quick way to tell the camera which face to focus on in the scene by having the camera prioritize faces at or near the selected AF point. AF-C (continuous) performance is disappointing relative to the quickly evolving competition: although continuous focus of an approaching or retreating subject with a single point chosen in the central portion of the frame works quite well (that's where the phase-detect AF points are), any mode involving having the camera track your subject as it moves around the frame, including face detection, can cause severe lagginess, misfocus, or simply missed shots due to the camera struggling to keep up.


* Note that DSLR AF doesn't benefit from F1.4 lenses over F2.8 or F4 lenses, as the AF system doesn't 'see' the extra light due to what can be thought of as virtual apertures over the phase-detect AF sensors. Mirrorless cameras, however, do make use of the extra light brighter lenses can provide.