Autofocus

The Panasonic S1R's contrast-detect autofocus system is generally fast and accurate, but not without its quirks.
Panasonic Lumix S Pro 50mm F1.4 | ISO 250 | 1/60 sec | F1.4

The Panasonic's S1R uses a contrast-detection autofocus system built around Panasonic's 'Depth-from-Defocus' technology. The way this works is the camera interprets the out-of-focus regions of the scene, according to the known characteristics of whatever lens is attached, to build up an understanding of depth. This ensures that it drives the lens focus an appropriate amount in the correct direction to achieve focus on your chosen subject quickly without too much of the usual contrast-detection 'wobbling' (except in AF-C mode, described in more detail further down this page). It generally works very well, but it's not without its shortcomings.

Key takeaways:

  • The S1R's Depth from Defocus system performs well, though it doesn't track moving subjects in depth (movement toward / away from the camera) as well as competitors
  • Face detection is effective for eyes, faces, bodies and pets, with a provision to use a button press to cycle through the detected subjects
  • The face detection can still result in false-positives, and sometimes 'loses' subjects just as you want to switch to them, making it hard to use with more than one person
  • The 'flutter' during continuous autofocus is distracting and makes it difficult to see if your subject is actually in focus

AF modes and face detection

Just as with the S1, the S1R comes with nine AF area modes and several of them can be tweaked to your liking. The focus mode button, which has a dial for switching between single, continuous and manual focus around it, can be found next to the 'AF-On' button on the rear of the camera.

Just like a pro-grade DSLR you can disable the AF modes you don't use, so that you only need to choose between the options you find useful.

The available AF modes are:

Mode Description
Face/eye/body detection Animal detection is optional. Detected faces can be switched by pressing the joystick inward or tapping a subject on the LCD.
Tracking Select a subject via the touchscreen. The size of the focus point cannot be adjusted.
225-area Whole scene multi-area AF mode
225-area (AF-C starting point) Select a single focus area and the camera will use all of the surrounding focus areas to track a subject. This option isn't shown by default and can found in the AF section of the menus.
Zone (vert/horiz) Select a series of rows or columns of the 225 AF points you want to be active
Zone (square) Off by default, you can select the size of the rectangular region of tje 225 AF points you want to be active.
Zone (oval) You can adjust the diameter and position of an oval region of the 225 focus points in the frame
1-area+ Like regular 1-area, but the selected focus point is surrounded by a slightly larger box, to keep your subject in focus if they slightly stray out of the focus area. Not limited to the 225 large AF regions
1-area Standard-issue single-point AF. Not limited to the 225 large AF regions.
Pinpoint A tiny AF point for focusing on things like stars
Custom [1,2, 3] Off by default, you can define your own AF point pattern, from the 225 large AF points, if your subject's movement doesn't suit any of the presets.

The face/eye/body detection is impressive, capable of detecting bodies that are quite far away. Compared to its peers, faces and eyes have to be relatively large in the frame to be detected as such, but once the camera has locked on to an eye it tracks it tenaciously, even if the face turns sideways - though as a caveat, we've noticed a number of our images were focused on a subject's eyelashes, and not necessarily their pupil or iris. Lastly, pet detection AF is quite effective.

We find the AF controls seen here to be well thought out.

You can switch between detected people/pets in the scene by pressing the joystick inward or using the touchscreen, but the camera will occasionally 'see' faces in non-human subjects and will intermittently lose and regain detection of others, often making it difficult to effectively cycle to your intended subject. Additionally, pressing inward on the joystick isn't always reliable; sometimes nothing happens, and at other times the camera thinks you've made a directional press, which snaps the camera out of face / eye detection mode.

Basically, the system works well for casual use with single subjects, but we wouldn't recommend enthusiast and pro photographers rely on it to quickly target the desired subject out of many in a scene.


Continuous AF

To test continuous AF performance, we first try to shoot a subject approaching at a steady speed using the central AF point. This lets us see how good the camera is at assessing subject distance and whether it can drive its lens to that point quickly. We shot this sequence (and the one that follows) using the Panasonic Lumix S Pro 70-200mm F4 lens at 1/1000 sec, with the aperture wide open and burst speed set to high (6 fps).

The S1R did well on this test, though you can see (partly because of the immense resolution of the files) that images 4 and 13 are slightly soft: this is consistent with our broader use of the camera in continuous autofocus. Generally, performance is quite good, but you will have the occasional soft image in the middle of a burst.

We then have the subject weave across the camera's AF region in a way the camera can't predict. This has the advantage that the approach rate varies as the subject changes direction. For this test we use the S1R's dedicated tracking mode at default settings, selecting our subject using the touchscreen.

On the whole, the S1R tracked our subject well, both when viewing on the LCD as it happens, and when reviewing the photos afterward. The tracking box stuck tenaciously to our subject as we were shooting, though you'll notice some softness throughout the images (images 5, 7, 13, 14, and 17). This level of softness isn't likely to be a huge problem, especially if you consider downsizing an option, but its performance is some way behind best-in-class.

AF-C customization

The S1 has four sets of continuous AF sets that you can use as predefined, or customize to your liking. Each of these sets has three options that can be adjusted:

Description Range
AF sensitivity How quickly the camera reacts to changes in subject distance. A higher number will bias the camera toward other subjects that enter the frame. -2 to +2
(Locked-on to responsive)
AF area switching sensitivity How quickly the camera switches to adjacent focus points when the subject moves. Only affecting 225-area modes. -2 to +2
(Locked-on to responsive)
Moving object prediction How sensitive the camera is to changes in the behavior or movement of your subject. Higher numbers are for subjects that change their speed unpredictably. 0 to 2
(Constant to variable)

The four C-AF sets have the following settings by default:

Set Description AF sensitivity AF area switching sensitivity Moving object prediction
1 Versatile and basic 0 0 +1
2 For subjects that go in one direction at a constant speed +1 -1 0
3 Continue tracking subject, ignoring obstacles -1 +1 +2
4 For subjects that change speed and move unpredictably 0 +1 +2

For the 'weave' portion of the bike test we tried both set 1 and set 4, but did not notice a significant difference in performance. Even so, it's worth trying out the various settings if you're not getting the results you expect.

Continuous autofocus in use

While the autofocus performance of the S1R is generally good, the DFD focus system can be a bit disconcerting at first. Just like high-end Panasonic Micro Four Thirds cameras such as the GH5 and G9, you'll end up with a good number of keepers if you just leave the camera in continuous autofocus.

Unfortunately, the focus 'wobble' through the S1R's viewfinder can be distracting, perhaps exacerbated by the shallower depth-of-field of a full frame sensor, the much higher-resolution viewfinder, or the increased speed of the autofocus communication and movement. Interestingly, it's better behaved when the camera is set to Face Detection mode, perhaps because the system is more robust and the camera can be more certain that it's focused on the right thing.

An unfortunate consequence of the contrast-based AF system is that the camera can hesitate to fire the shutter with erratically moving subjects, due to the autofocus system playing catch up or hunting. This can mean missed shots with faster moving subjects.