Pentax Q-S1 Review

General Image Quality

Now, let's take a look at what matters the most: the Q-S1's image quality.  It is well known that sensor size largely dictates how clear and detailed digital images will turn out.  At 1/1.7" diagonally, the QS-1's sensor is about 50% larger than the 1/2.3" sensor found in Q bodies preceding the Q7.  Even at this size, however, the new sensor is still only classified as an upper-end point-and-shoot sensor.  The Pentax Q system is currently the only mirrorless system to use these small chips: other systems employ 1" (2.5x larger), micro four-thirds (5x larger), or APS-C (8-9x larger) sensors.  Smaller formats also suffer from other issues, such as diffraction: indeed, you don't want to be stopping down your Q-S1 as much as you would a DSLR, as you will quickly see details disappearing from your images.

Thus, on a theoretical level, the Q-S1 doesn't have much going for it.  Its image quality is the same as that of the Q7.  But this doesn't mean we can jump to conclusions. Sensor technology has evolved tremendously over the course of the past decade, so could it be that the Q-S1's sensor is actually good enough for everyday shooting?  We believe the answer is "yes": the Q-S1 does quite well in practice, especially if you're just interested in capturing snapshots everywhere you go.

Unedited Q-S1 Sunset Photo (click for full size)

The remainder of this page is broken up into sub-sections that take a closer look at various aspects of the Q-S1's image quality.

RAW Files

The Pentax Q-S1 is of course capable of capturing photos in a 12-bit RAW format.  Files are saved in Adobe's universal .DNG standard.  Shooting in RAW gives you considerably more control over your photo at the expense of a longer post-processing time, and you're also able to extract more detail and more dynamic range than you would from a JPEG.  Note that if you decide to use the Pentax desktop software bundled with your camera, you can apply any JPEG "custom image" presets retroactively.

For the best results, we recommend shooting in RAW+ with the Q-S1: this allows you to use the camera's JPEG files for simple subjects and the DNG files when corrections must be made to the exposure.

The noise reduction that the Q-S1 applies to its JPEG files removes or smudges a considerable amount of detail, even at base ISO.

Detail

The Q-S1 renders plenty of detail in nearby subjects, and you might even observe moire at times. This shows that the resolving power of the camera, even when paired with the 5-15mm kit zoom, is very good.  The photo below includes a 100% crop alongside the original scaled image, developed from RAW.

At longer distances, however, the Q-S1 struggles to render fine details, as is to be expected.  Our main gripe about this camera is that more often than not, there simply isn't enough resolution to allow for any significant cropping.  If we were to only keep the houses in the image below, for instance, it would not look good, even at a small web resolution.

Q-S1 full-size JPEG sample: click to view (download DNG)

Diffraction

The smaller a camera's sensor, the earlier diffraction sets in.  In other words, if you stop down the lens too much, you will start seeing less and less detail in your images.  The test photos below were taken with the 5-15mm set to 10mm; the ISO was set to 100.

F4
F5.6
F6.3
F7.1
F8

Shooting wide-open or close to wide-open will give you the best results, as the image quality worsens noticeably at F6.3 and below.  This is a bit restrictive as it means that you'll have to rely more often on the shutter speed to control exposure. 

Fortunately, though, this is a noticeable improvement over the Q or Q10, which start exhibiting diffraction about half a stop earlier based on our tests.

Field of View

The Q-S1 and Q7 "see" more of the frame than the Q or Q10; this means that all lenses used with it will have a wider field of view at the same focal length.

Pentax Q-S1/Q7 field of view vs. cropped Q/Q10 field of view (red)

A consequence of this is that certain lenses- namely the 03, 04, and 05 lenses (details at the end of this review) will operate in a "crop mode" on the Q-S1, which yields a lower resolution and a field of view corresponding to that of the Q/Q10.

When using other lenses, such as the 01 prime, 02 zoom, 06 zoom, or 08 zoom, you may also need to compensate for more geometric distortion and other aberrations than on the Q.

Bokeh

Getting nice bokeh with a sensor as small as that of the Q-S1 is tough.  It's a bit easier than with the Q or Q10 at wider focal lengths, but if you really want to see some smooth backgrounds, you'd be better off with a DSLR.  This also means that we don't recommend the Q-mount system for portrait photography.

Pentax Q-S1 w/02 lens at 10mm, F3.5 (click for full size)

The Q-S1 also includes a "blur control" mode, which adds a simulated blur effect to the image using software.  Photos taken in this mode aren't particularly appealing (see our Pentax Q review for samples).

Exposure, Dynamic Range, and White Balance

We found the Q-S1's white balance to be accurate in daylight, though it does struggle a little in artificial lighting compared to the latest Pentax DSLRs.  It often makes colors from artificial light sources warmer than they should be, thus introducing a yellow color cast.

The Q-S1's metering is generally very accurate, but the camera has a tendency to blow highlights and has visible noise in shadows.  On a sunny day, you will often need to bracket in order to capture detail in the sky.  But if you get the exposure right, and if you shoot in RAW to remove noise, the Q-S1 has enough dynamic range for shooting scenes with varied lighting.  Noice how well we were able to recover the shadow detail and remove noise while in RAW mode; click to enlarge and compare:

Cropped Out-of-camera JPEG (download original)	Adjusted RAW File (download DNG)

While a dynamic range test is outside the scope of this review, it is our impression that the dynamic range of the Q-S1 is very similar to that of its predecessors: about 11 stops.  This is some three stops less than the dynamic range of current Pentax DSLRs, which makes the Q-S1 much less forgiving as far as exposure goes.

Most users will be happy with the out-of-camera files from the Q-S1 except when highlights dominate the frame; should this be the case, we recommend underexposing by a third of a stop.

JPEG Image Engine

As we mentioned earlier, the Q-S1 allows you to customize the appearance of its JPEG files via a "custom image" menu.  In addition to choosing from one of 11 presets, you can manually tweak the following parameters:

• Saturation
• Hue
• High-key/low-key filtering
• Sharpness
• Contrast
• Color filter (B&W only)
• Toning (B&W, muted, and bleach bypass only)

The default preset, "bright", delivers pleasing images with warmer color tones compared to the "natural" preset.

Depending on your shooting style, we recommend either the "bright", "natural", "landscape", or "vibrant" presets.  Black and white conversions are best done in post.

Over-Sharpening and Noise

While we have nothing against the color tones available via the JPEG engine, we've observed that the Q-S1 likes to over-sharpen its JPEG files when using default settings.  It also applies noise reduction a bit too liberally.  This manifests itself as glowing edges and blurred detail, plus occasional noise where it doesn't belong.  We therefore recommend either decreasing the JPEG sharpness or simply shooting in RAW for the best image quality.

Let's consider the scene below:

Test scene: Original JPEG | DNG RAW

When comparing a full-size crop of the original JPEG file to our developed RAW file, we observe noise in the sky and glowing edges around the leaves in the former.  These artifacts shouldn't be there as the Q-S1's sensor is otherwise good enough to keep the image noise-free and clean at ISO 100.  Note that all lens corrections were disabled when this image was shot and processed.

100% Crop - From JPEG	100% Crop - From RAW

Shake Reduction

Thanks it its mechanical shake reduction, the Q-S1 compensates for up to 3 stops of camera shake when hand-held.  We were able to successfully hand-hold it at night at shutter speeds as slow as 1/8s at ISOs of 1600 and 3200.

Read on for a close look at the Q-S1's high-ISO performance as well as our image quality verdict.