Pentax Q-S1 Review

Autofocus and MF Assist

The autofocus system in the Pentax Q-S1 is that same as that of the Pentax Q7 in stills mode.  The camera has also received a new continuous AF option for videos which we will discuss on the video page.  Compared to older models, the Q-S1's AF system is a big step up. Its AF feels faster and more responsive than that of the Q or Q10, and it shows what's in focus more effectively, both in playback mode and at the time of capture.

The Q-S1 shows the user exactly which AF points are in focus, which makes it much easier for the user to see if the camera locked focus on what it was supposed to.  When shooting photos of non-rectangular objects, such as lamps or trees, the AF points that lock focus should create a pattern that roughly matches the shape of those objects.  The screenshot below compares the Q-S1's AF display with that of the Q.


Q-S1 - AF points correspond roughly to shape of the subject


Q - only a small area is shown as being in focus even though much of the CD case is in fact sharp

The Q-S1, like the Q, can use up to 25 AF points at a time.  Spot focusing, face detection, and rudimentary tracking are also supported (the tracking doesn't really work in practice). The Q-S1's AF point selection screen has been redesigned, giving the user a better idea of where the AF point boundaries lie, and which points are being used.  The Q-S1 supports rectangular areas of 1, 9, or 25 points.  The Q supports these sizes as well as a 1x3, 3x1, and 5-point AF layout; the additional layouts are not needed by the Q-S1 due to the way that it displays what's in focus (as shown above).


Q-S1 - redesigned AF point selection screen


Q - old AF point selection screen

Autofocus Speed

So how fast is the Q-S1's AF in practice?  In order to find out, we set up an indoor test scene with three contrasty subjects approximately 1.5 meters (5 feet) away from the Q and Q-S1.  We experimented with natural lighting (10EV) as well as artificial lighting (5.3 EV and 2.3 EV) and very low light (1.3 EV), measuring the time it took for each camera to focus from minimum focus as well as infinity focus.  We tested the Q with the original and latest firmware versions.

The table below shows the time it took each camera's AF system to lock on and release the shutter in 9-point AF mode.  For each test, 5 readings were taken using a stopwatch.  The median reading, rounded to the nearest tenth of a second, is shown in the table.  Both cameras used the same 5-15mm lens set to 15mm.

10EV
5.3EV
2.3EV
1.3EV**
Inf. Min. Inf. Min. Inf. Min. Inf. Min.
Q-S1 & Q7 0.4s 0.5s 0.5s 0.8s 0.6s 0.9s 1.0s 1.5s
Q (v1.12) 0.5s 0.6s 0.6s* 1.0s* 1.1s* 1.5s* 1.1s 1.5s
Q (v1.00)
0.5s 0.6s 1.2s* 2.1s* 1.3s* 2.3s* 1.4s 2.5s

*AF assist light fired | **AF assist light disabled

As the results above show, the Q-S1 has an advantage the Q across the board, but the difference is only significant in low ambient light. This means that you won't notice much of a speed improvement during the day, but when shooting at night, it's a whole different story!  The Q-S1 has the same AF performance as the Q7.

The Q-S1's specifications state that it can focus in lower light: at 0EV and up.  This is one stop better than the Q or Q10.  At 1.3EV, however, the Q-S1's performance proved to be very similar to that of the Q.

In the field, we set the Q-S1 to 25-point AF and we generally had no issues with it.  During the day the AF system is quick and reliable, and it rarely misses focus except when shooting close-ups, which require you to select a smaller number of AF points or to pinpoint the location of your subject.

In our tests, neither camera failed to lock focus; as long as there is plenty of contrast in the subject you should therefore be in good shape. We do not recommend spot AF (i.e. single-point AF) as it doesn't give the camera much data to work with when focusing, even when it's very bright.  9-point AF is what you should opt for instead if you wish to focus on subjects in the center of the frame.

We also tested the time it took for each camera to re-confirm focus.  This operation isn't instant: it takes about as long as focusing from infinity. 

Focus Peaking

In order to help you out when focusing manually, the Q-S1 has a focus peaking feature that tries to highlight edges when they are in focus.  Objects that are in focus are outlined in white, as shown below.

Unfortunately, the focus peaking only works well in high-contrast areas of the image, as the white edges are hard to see otherwise.  At times, the edges aren't even shown, or are very difficult to spot, as in the scene below.


Focus Peaking On


Focus Peaking Off

When focusing manually, the Q-S1 also supports live view magnification of 2x, 4x, and 6x.  The resolution of the magnified image isn't the best, and you will likely still find if difficult to manually focus with long lenses, but it's a start.

We recommend disabling focus peaking when using the magnification feature.  With focus peaking on and the live view magnified, you mostly see a bunch of noise on the screen from erroneous focus peaking data. 

Overall, the Q-S1's focus peaking and manual focus assist systems are in need of improvement.  A higher-resolution display would undoubtedly come in handy in facilitating a more user-friendly and more discernible way of showing focus peaking, and we strongly feel that this change needs to be made given the fact that no EVF option exists for the Q-S1.  Focus peaking on Pentax DSLRs, which have twice the screen resolution, is much more useful.

Focusing Verdict

The Pentax Q-S1's autofocus system is excellent for everyday shooting as well as low-light shooting.  With faster response times and an explicit display of what's in focus, the Q-S1 has the best contrast detect autofocus system that we've seen to date in any Pentax.  The speedy and silent AF motors found in Q-mount lenses go together perfectly with the Q-S1's reliable AF.

In terms of focus peaking and manual focus assist tools, the Q-S1 still has a ways to go.  It's tough to focus manually with this camera, as blowing up a low-resolution image on a low-resolution monitor won't always be enough to see fine details, especially with adapted telephoto lenses that have a narrow depth of field.

Reliable continuous tracking is also not currently possible, as the Q-S1 has no PDAF sensors.


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