Pentax Q Optics
Pentax Q Optics
As you'd expect given that it ships with a brand-new lens mount, the Pentax Q isn't available body-only. In the US market, it's currently available in only one kit, which includes the 01 Standard Prime lens, an 8.5mm f/1.9 optic that's equivalent to a 47mm lens on a 35mm camera. Some overseas markets offer a choice of kit lenses, either replacing or supplementing the prime lens with the 02 Standard Zoom. With a 3x optical zoom range, this lens offers focal lengths from 5 to 15mm with a variable f/2.8 to f/4.5 aperture. 35mm equivalent focal lengths range from 27.5 to 83mm.
Both lenses are part of what Pentax is referring to as the 'High-Performance series' (and at this time, they're the only models in the series). They have metal lens mounts, mix metal and plastic construction in the rest of their makeup, and despite their small size and weight, achieve a feeling of good quality. They feature 40.5mm filter threads, a nice touch since that means they can both share the same filters, and their center-pinch lens caps are interchangeable. They also have fly-by-wire manual focusing, and are internal focusing designs. Their front elements don't rotate when focusing or (for the zoom) when adjusting focal length. Both have 5-bladed apertures that double as in-lens shutters, and allow maximum shutter speeds of 1/2,000 second, with internal flash sync possible at up to the same speed. They also include built-in, optional two-stop neutral density filters. Minimum aperture in both cases is f/8.0. As you'd expect, they also include Pentax's lens coating to combat flare.
Optical construction of the 01 Standard Prime kit lens consists of eight elements in five groups, with two aspherical elements. Minimum focusing distance is 20cm or 7.9 inches for a maximum magnification ratio of 0.05x or 1:20 equivalent. Length is 23mm or 0.9 inches, while maximum diameter is 46mm or 1.8 inches. Weight is just 96 grams or 1.3 ounces, without the optional lens hood. Given that it's included with all Q camera bodies in the US market, this lens isn't available for purchase separately here. In some other markets where it's possible to buy the Q with just the zoom lens, the prime may also be available as a separate product, however.
For the 02 Standard Prime lens that's available as a kit model in some markets, the optical formula is eight elements in seven groups, including four extra-low dispersion glass elements. Minimum focusing distance is 30 cm or 11.8 inches across the zoom range, for a maximum magnification of 0.06x or 1:16.7 equivalent at the telephoto position. The optical zoom ratio is 3x, with a rotary mechanical zoom control, and the lens extends by about 3/8 inch (10mm) or so at the wide angle position. (Its most compact size is achieved at an actual focal length of 12-13mm, although it only extends negligibly at full telephoto.) There's no zoom lock, but given the extremely light weight of the lens, it's unlikely that zoom creep would ever be an issue, even with several filters and a hood attached. Length is 48mm or 1.9 inches when the lens is retracted, and maximum diameter is also 48 mm or 1.9 inches. Weight is about 175 grams or 3.4 oz, without the optional lens hood. List pricing for this lens is $300 in the US market.
The Pentax Q features a brand new bayonet lens mount dubbed the Q mount. It's not backwards-compatible with any previous lenses, although Pentax has plans to offer an adapter offering K-mount compatibility, with some limitations (and a fairly extreme focal length crop). The Pentax Q-mount is designed to accommodate a 1/2.3-inch type (7.7 mm / 0.30 inch diagonal) image sensor with sensor-shift stabilization mechanism, and the reduced backfocus distance of a mirrorless design.
Pentax's Q-mount lenses are unusual in that the company defines them as two distinct groups, separated by price and feature set. In the kit lens section above, we've already detailed the 'High-Performance series', which launches with two lens models. The remaining three lenses available at launch make up the 'Unique series'. These are aimed at lower cost, and replace the metal mount with a plastic one, much like the company's DA-L lenses on K-mount cameras. More importantly, though, they don't include the in-lens shutter mechanism of the 'High-Performance' models, which brings a couple of key limitations. They can show significant rolling shutter effect in still images, if your subject is in motion. They also limit flash sync speed to just 1/13 second.
Additionally, they have a fixed aperture, drop autofocus capability and the built-in ND filter, don't include filter threads or provision for lens hoods, and most models don't feature a Pentax SP lens coating. Another cost-saving difference from the High-Performance series lenses can be found in their lens caps. Unlike their more expensive siblings, which ship with a traditional spring-loaded center pinch lens cap, the Unique-series lenses include a soft, plastic cap that simply presses around the outside of the lens barrel, and is held in place by friction. The front caps for the fisheye and toy wide lenses are interchangeable, while the toy tele lens is slightly larger than those for the other Unique models.
Although the Unique-series lenses all include mechanical manual focus dials, they have a very short throw indeed. It takes only around an eighth of a turn to traverse the entire focus range, and you do have to pay attention to focusing carefully: all three lenses will go beyond infinity.
The PENTAX 03 Fish-eye is the sole model in the series to include an SP coating, and has a fixed f/5.6 aperture, and a 3.2mm focal length (17.5mm equivalent), yielding a 160° field of view. Pentax describes it as a pan-focus design, meaning that depth of field is sufficient to keep both your subject and background sharp, unless the subject is very close to the camera. The optical formula is six elements in five groups, and minimum focusing distance for this lens is rated at 89mm or 3.5 inches, while maximum magnification is 0.06x / 1:16.7. Length is 30mm or 1.2 inches, while maximum diameter is 41mm or 1.6 inches. Even though its weight is just 29 grams or 1.0 ounces, this is actually the heaviest current unique-series lens. Pricing for this model is in the region of US$130.
The remaining two lenses are intended to appeal to fans of Lomo photography, and are dubbed "toy" lenses by Pentax. The Pentax 04 Toy Lens Wide has a fixed f/7.1 aperture, and a 6.3mm actual focal length (35mm equivalent), yielding a 64° field of view. The optical formula is four elements in three groups, and minimum focusing distance for this lens is rated at 71mm or 2.8 inches, while maximum magnification is 0.15x / 1:6.7. Length is 25mm or 1.0 inches, while maximum diameter is 41mm or 1.6 inches. Weight is just 21 grams or 0.7 ounces. This lens is priced at a very affordable US$80 or thereabouts.
Finally, the Pentax 05 Toy Lens Telephoto has a fixed f/8 aperture, and an 18mm actual focal length (100mm equivalent), yielding a 24.5° field of view. The optical formula is extremely simple: just three elements, none of them grouped, and minimum focusing distance for this lens is rated at 26.9cm or 10.6 inches, while maximum magnification is 0.08x / 1:12.5. Length is 20mm or 0.8 inches, while maximum diameter is 41mm or 1.6 inches. The weight is a remarkable 18 grams or 0.6 ounces; this is both the smallest and lightest Q-mount lens as of this writing (Feb 2012). As with the other toy model, pricing for this lens is approximately US$80.
Pentax revealed development of several additional Q-mount optics expected to be available sometime during 2012, although this is subject to change. These include a telephoto zoom lens of unspecified focal length and aperture, a pinhole lens tentatively known as the 'Mount Cap Lens', and a mount adaptor allowing use of K-mount lenses on Q-mount bodies. This last is particularly interesting, given that it includes a built-in shutter unit, but sadly it doesn't provide for autofocus or automatic aperture control. (There's an aperture dial allowing apertures from the maximum of the lens to f/8, however.) Slated to go on sale from Spring 2012, pricing isn't available for the adapter; nor do we have pricing info for the new lenses.
Following are detailed specifications for all five Q-mount lenses available as of February 2012.
The Pentax Q offers five autofocus modes: Face Detection, Tracking, 25-point AF Select, Select, and Spot. Of course, manual focus is also available. Like almost all compact system cameras, all modes rely on contrast detection algorithms that analyze data streaming off the image sensor.
In Face Detection mode, the Pentax Q can detect up to twelve faces simultaneously, and automatically selects one of these faces for autofocus and autoexposure determination. A yellow frame is placed around this face, while white frames appear for other faces. If no faces are present, the camera falls back to a centered 9-point mode.
The 25-point AF Select mode divides the image frame--with the exception of the extreme edges--into an array of five by five areas. The camera automatically selects the focus point, and it's possible to limit the number of points to either 9-point (a 3x3 array), 5-point (a plus-shaped array), 3-point (either vertical or horizontal), or single-point. All of these reduced-point modes allow the active area to be moved around the frame, and can't overlap the edge of the frame, except for the 5-point mode. This last can be placed so that the center point sits on one edge of the array, or in the extreme corner.
The Tracking mode provides a single, smaller AF point at the center of the frame, and attempts to follow the subject as it moves around the frame. The Select mode offers a smaller AF point size, and lets you position that single point within a much finer-grained grid of 47 x 33 locations covering most of the image frame, apart from the extreme edges. Finally, Spot mode simply locks focus from the very center of the image frame.
Note that there isn't a separate Continuous Autofocus mode on the Pentax Q. Instead, this is enabled only when the camera is placed in Moving Object, Night Snap, Pet, Kids, or Stage Lighting scene modes.
When using manual focus, you can magnify the image by either 2x or 4x courtesy of the MF Assist option in the Focus Settings menu, and activated by pressing the OK button, and this defaults to zooming at the center of the frame, although you can move this area around the frame with the arrow keys, and roll the E-dial to change between the two zoom levels when active. The four-way controller can be used to move the magnified area around the frame, and if set to Contrast Detection AF, the focus point moves so as to remain in the center of the view. Pressing the OK button a second time immediately returns the view to the center, and when you half-press the shutter button, the magnified view is immediately canceled to allow image framing.
To help with focusing on nearby subjects in low ambient lighting conditions, the Pentax Q includes an AF assist lamp, which can be disabled in the Custom menu.
Like its SLR cameras, the Pentax Q includes an in-body stabilization system, or 'Shake Reduction' in Pentax parlance. Unlike lens-based systems which rely on each lens to provide stabilization capability, the in-body stabilization functions with all Q-mount lenses. The potential disadvantage is that sensor shift designs aren't necessarily as effective at correcting for shake on lenses with longer focal lengths, compared to lens-based stabilization. This, as yet, isn't something that Q owners need worry about, given that the no current Q-mount lenses offer more than a 100mm focal length. That may change when the company ships longer focal length lenses for the Q mount, however. In the meantime, Shake Reduction comes in very handy to freeze blur from camera shake in low-light conditions, although obviously only a higher shutter speed can help with subject motion.
According to Pentax, the Q's Shake Reduction can provide up to a 4 stop reduction in blur. Through the Custom menu, you can opt to have Shake Reduction performed only during image exposure, or during framing as well. Disabling the function isn't likely to save much power, however, as the system must remain active if only to hold the sensor still during exposure.
The Pentax Q also includes a Pentax dust removal system, branded as DR II, the same system that debuted in the Pentax K-7 and also features in the K-5. Like these models, the Q relies on the combination of an SP coating on the low-pass filter to keep dust from adhering in the first place, and high-frequency vibration using a dedicated piezoelectric element to try shake dust off the sensor. Our past testing has found these systems to be more effective, compared to systems like those in Pentax's entry-level SLRs, which instead use lower-frequency vibrations induced using the sensor shift mechanism.
Unlike the company's SLRs, the Pentax Q doesn't offer a Dust Alert function, however, so you'll need to take your own test images if you want to confirm if there's any dust adhering to the OLPF that merits a manual sensor cleaning.
Distortion Correction. The Pentax Q can correct for lens distortion in-camera, when using Q-mount lenses. This feature corrects for both pincushion and barrel distortion for 'High-Performance' series lenses, helping ensure lines that should be straight appear so in the final image. No correction is available for 'Unique' series lenses.
Kit Lens Test Results
Fair performance with the 8.5mm f/1.9 kit lens.
8.5mm @ f/5.6
The Pentax Q is available bundled with a Pentax-01 8.5mm f/1.9 lens (35mm equivalent is 47mm). The lens is reasonably sharp at f/5.6, with minimal softness in the corners and fairly strong detail throughout the rest of the frame, though finer details are a bit fuzzy. (We normally shoot our Far-field test at f/8 for interchangeable lens cameras, however because the Pentax Q's sensor is much smaller than most, we shot it at f/5.6. A larger aperture such as f/4 or f/2.8 would have likely performed better in terms of center sharpness.) Coma distortion in the trees was low, and chromatic aberration appears well controlled, with only a hint of flare around some of the white trim.
A larger-than-average minium area, with good detail in the center. Flash had trouble up-close, producing a very dim exposure.
Macro with 8.5mm kit lens, f/1.9
Macro with Flash, f/1.9
The Pentax Q's macro performance will depend entirely on the lens in use. However, with the 8.5mm kit lens, the Pentax Q captured a somewhat larger-than-average minimum area measuring 3.53 x 2.64 inches (90 x 67 millimeters). Resolution and detail were both good in the center of the frame, with moderate softening in the extreme corners. (Most lenses have some softening in the corners at macro distances, and stopping-down to a smaller aperture generally helps.) The built-in flash had trouble at this close distance, producing a very underexposed image. You'll likely have to stick to external lighting for up-close shots like this one with the Pentax Q.
Very low geometric distortion with the 8.5mm kit lens in JPEGs with Distortion Correction enabled.
Distortion Correction On: Pincushion distortion is less than 0.1 percent
Distortion Correction Off: Barrel distortion is about 1.4 percent
The Pentax Q's 8.5mm kit lens produced under 0.1 percent pincushion distortion in JPEGs, which is negligible, though it's interesting that distortion was pincushion (slightly overcorrected barrel distortion). Turning off the camera's Distortion Correction feature resulted in barrel distortion that was quite high, at just under 1.4 percent. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).
Chromatic Aberration and Corner Sharpness
Moderate chromatic aberration with the kit lens, with strong blurring in the right corners.
8.5mm @ f/1.9: Lower right
C.A.: Moderate and somewhat bright
Softness: Very soft
8.5mm @ f/1.9: Center
Chromatic Aberration. Chromatic aberration in the corners with the Pentax Q's 8.5mm kit lens is moderate and a little bright, though some of this is no doubt affected by some strong blurring in the right corners. (CA is less in the left corners.) Chromatic aberration in uncorrected RAW files is similar, but the camera may be applying CA correction to RAW files (there's no way we can tell).
Corner Softness. The Pentax Q's 8.5mm kit lens produced very soft corners on the right side of the frame, though the left corners showed only minor blurring. In the center, sharpness was very good. (Corner sharpness generally improves when a lens is "stopped-down" a couple of f-stops below full aperture.) There's a bit of corner shading visible as can be seen by the darker corner crop, but light fall-off is actually quite low for the brightness of the lens (f/1.9).
8.5mm @ f/5.6: Lower right
C.A.: Fairly low
Softness: Mild blurring
8.5mm @ f/5.6: Center
Softness: Slightly soft
Chromatic Aberration. With the aperture stopped down to f/5.6, chromatic aberration in the corners with the Pentax Q's 8.5mm kit lens is fairly low, showing really only a hint of a red or green fringing along target lines.
Corner Softness. Corner sharpness is better at f/5.6, with only mild blurring in the corners compared to what we saw at f/1.9, but the center is a touch soft, probably due to diffraction. Vignetting (corner shading) is very low when stopped down to f/5.6.
8.5mm @ f/2.8: Lower right
8.5mm @ f/2.8: Center
During our testing, we found that our 8.5mm f/1.9 lens is sharpest in the center at around f/2.8, however corners on the right side are still quite soft though not as soft as f/1.9. See above. A second copy of the lens tested similarly. We'll be testing this lens on SLRgear.com, so stay tuned for test results at a full range of apertures. Bottom line, avoid apertures smaller than f/2.8 for maximum sharpness.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Pentax Q Photo Gallery .