Ever the innovator, Pentax is the first company to offer a DSLR camera in colours other than black and grey. The 12.4 megapixel K-x model will be available in a choice of white or black, as well as bright red and dark navy. Kit lenses are available to match. Its small body makes the K-x one of the most compact, lightweight models in its class. However, this camera also provides heaps of in-camera adjustments plus the ability to record HD video clips.

The K-x sits between the 10.2-megapixel, entry-level K-m and the 14.6-megapixel K-7 and shares features of both models. A comparison of specifications shows it to be remarkably good value for money in its market sector. The main differences between the three models are shown in the table below.

The review camera was supplied to us with the smc Pentax-DA 18-55mm f/3.5-5.6 AL lens, which is the standard kit lens. A review of this lens can be found on the Photo Review website. The K-x is also offered in a twin-lens kit with the 55-300mm DAL lens.

Build and Ergonomics
Physically the K-x is quite similar to the K-m model, as shown in the illustrations below. It has the same body dimensions, although for some unknown reason it's 10 grams lighter.

The Pentax K-m (left) and K-x (right) cameras compared. (Source: Pentax.)

It also has the same stainless-steel chassis, which is covered by a fibre-reinforced plastic polymer, and the same viewfinder. The generous hand grip has a rubberised coating for comfort and security and the camera is well-balanced and small enough to allow users to shoot one-handed.

Front view of the Pentax K-x body in bright red, with the lens removed to show the mirror box. (Source: Pentax.)

Front view of the Pentax K-x body in white with matching 18-55mm kit lens. (Source: Pentax.)

Front view in black with the 18-55mm kit lens and flash up. (Source: Pentax.)

Rear view of the Pentax K-x in black. (Source: Pentax.)

Top view with the 18-55mm kit lens fitted. (Source: Pentax.)

Build quality is very good for the camera's price tag. A single slot is provided for SD/SDHC memory cards. The grip has a rubberised coating for comfort and security and the controls are all easily accessed.
The battery compartment, which accepts four AA batteries, has a close-fitting lid. It's located in the base of the grip. A metal-lined tripod socket lies mid-way across the base plate, in line with the optical axis of the lens.

Unlike the pricier K-7, the K-x lacks weatherproof sealing. However, all seams are snug and the card compartment door is sturdy and close-fitting.  Another key to the lower price tag is the LCD monitor, which is only 2.7-inch diameter with a relatively low resolution of 230,000 dots. No data LCD is provided so the monitor must double as a data display.

It also supports the camera's Live View capabilities - which include widescreen HD video capture at 720p resolution (1280x720 pixels) with the popular ‘cinematic' 24 frames/second frame rate. Contrast-detect, phase difference detection and Face Detection autofocus (up to 16 faces) are supported in Live View mode.

The viewfinder appears to have been carried over from the K-m. It's not particularly bright and covers only 96% of the sensor's field of view with roughly 0.85x magnification. A slider on the top of the housing provides easy diopter adjustment. The eyecup surround is rubberised but not particularly deep. 

Status indicators showing the flash status, picture mode, shake reduction, shutter speed, aperture, focus indicator, number of recordable images/EV compensation/ ISO sensitivity and focus mode are shown below the image. EV compensation can be adjusted without taking your eye from the viewfinder by pressing the +/-AV button and rotating the e-dial.

In addition to the monitor, the rear panel carries a suite of button controls that will be familiar to most compact digicam users. The arrow pad has a central OK button, with the vertical buttons accessing the drive and flash modes and the horizontal buttons the white balance and ISO settings. Between the arrow pad and monitor four buttons are arranged vertically: Play, Live View, Info and Menu.

There's a single ‘e-dial' wheel above the Play button, which also accesses the playback zoom and index modes. A small AF/AE-lock button is located in the top right corner of the rear panel, while in the top left corner is a button that doubles for flash-up and delete.

The top panel carries the standard Pentax mode dial, which is somewhat over-crowded with shooting modes. There are 14 in all, including a prominent green Auto Pict mode, a SCN mode that accesses a sub-menu containing 10 illustrated pre-sets, the Movie mode, P, Sv, Tv, Av and M modes, a flash-off mode and additional pre-sets for Night Scene Portrait, Moving Subject, Macro, Landscape and Portrait modes.

Also on the top panel are buttons for exposure compensation and Green button, which replaces the Help button on the K-m. You can assign one of the following functions to this button: Custom Image, Optical Preview, Digital Preview, Digital Filter, RAW+JPEG and Centre AF Point selection. This button also provides a depth-of-field preview in optical and digital preview modes.

The built-in flash lifts its head approximately 45mm above the camera body when you press the flash-up button. It has to be pushed down manually if you don't want it to fire. The sensor-shift Shake Reduction mechanism and dust reduction system have been carried on from the K-m.

Controls
Pentax has revamped with user interface on the new model to provide quicker access to key camera settings. Although the main menu remains unrefined, the graphic display on the monitor has evolved since the K-m and K7 were released and adopts the best features of each model. When you press the Info button, you see a graphic control panel showing the selected shooting mode plus current camera settings. You can navigate through the options with the arrow pad buttons.

The new graphic user interface on the Pentax K-x.

The arrow pad provides a different, ‘close-up' view of individual settings but, again, increasing or decreasing values or moving from one setting to the next is done by toggling the arrow pad buttons. Pressing the OK button locks the setting in.


Adjusting sensitivity via the new graphic user interface.

The Scene sub-menu contains the same 10 illustrated pre-sets as found in the K-m, with illustrated examples of when the selected setting should be used. The interface is the same as on the K-m.


The Scene mode interface.

As in the K-m, the first page of the K-x's Shooting menu carries a Custom Image setting that lets you choose from six Image Tone modes: Bright, Natural, Portrait, Landscape, Vibrant and Monochrome, all involving some degree of image processing. They're largely self-explanatory and usable only in the Exposure modes (P, Tv, Av, Sv and M) - but only for JPEG capture.

Each Custom Image setting is individually adjustable for the following parameters: saturation, hue, contrast, sharpness, toning and filter effects. The K-x also provides the same range of Digital Filter effects for JPEG capture as the K-m. However, the new camera boasts 16 different filters including Colour Extract, Retro, Soft, Starburst, Toy Camera plus a custom filter for building multiple effects. Photographers may also apply multiple filters to a single image for customised effects.

Another special effect is the Cross Processing mode which, like the filter effects, only works for JPEG capture. Designed to replicate of processing colour film in the wrong chemicals, it changes the colour balance and contrast of the image. Reds are suppressed and greens are enhanced in this mode, which also increases brightness a little and reduces contrast. An example is shown below.


The image on the left is a normal shot, while the one on the right was taken with the Cross Processing effect applied.

Multi-exposure capture is similar to the K7 and is selectable on page 2 of the shooting menu. It's usable with the full auto, P, A, S and M shooting modes but not in the movie mode or with Cross Processing, HDR capture or Digital Filters or when exposure bracketing or lens corrections have been set. Users can set the number of shots to be superimposed anywhere between two and nine and enable the camera to automatically adjust exposure levels to produce a correctly-exposed result.

The HDR (high dynamic range) capture setting from the K7 has been carried over to the  K-x and is also provided on page 2 of the shooting menu. With this setting, the camera records three frames in rapid succession, one underexposed, the next with correct exposure and the last overexposed. The images are combined in the camera to produce one composite image with an extended dynamic range.

The HDR mode works best when the camera is tripod-mounted because it takes roughly 1/8 second for the three shots to be captured. Processing takes approximately half a minute, during which time the camera locks up. Three HDR modes are provided: Off, Standard and Strong. It only works for JPEG capture.

A new CTE (Colour Temperature Enhancement) setting has been added to the white balance pre-sets. According to the user manual, it's designed to ‘keep and strengthen the colour tone of the light source in the image'. It's used to counteract the automatic white balance processing, allowing you to retain, for example, the orange cast of incandescent lighting or the green bias of a shot of a Coffs Harbour golf course.

Another unusual feature in a camera at the K-x's price point is the provision of in-camera lens corrections which enable photographers to compensate for rectilinear distortions and lateral chromatic aberration inherent in the lens they use. These corrections are only possible with DA, DA L or D FA lenses and won't work with accessories like tele-extenders and close-up rings.

The main menu also allows users to set a Custom Image ‘finishing' tone when the P, A, S and M shooting modes are used. This sub-menu provides adjustments for saturation, hue, brightness (high/low key adjustment), contrast, sharpness and toning and provides a range of colour filter effects for monochrome photography. These simulate the effects of colour filters on B&W film and include green, yellow, orange, red, magenta, blue, cyan and infrared.


Options provided in the Custom Image sub-menu.

Sensor and Image Processing
The CMOS sensor in the K-x appears to have been made by Sony. It's 0.1 mm larger horizontally and vertically than the CCD chip in the K-m and has 12.9 million photosites in total, with 12.4 million of them used for recording the image.

The Pentax PRIME (Pentax Real Image Engine) image processing engine has also been upgraded and appears as version II in the K-x. It underpins the camera's fast 4.7 frames/second burst capture speed and 1/6000 second maximum shutter speeds, enabling the larger files to be processed and stored faster. In-camera 12-bit analog/digital conversion is also supported.

The new processor enables the camera to support a new High Dynamic Range (HDR) image capture mode that replaces the dynamic-range expansion function in the K-m. It blends three bracketed images into a single picture with improved shadow, highlight and midrange detail. Sensitivity expansion is now offered for up to ISO 12,800 via a custom function and down to ISO 100 beyond the standard ISO 200-6400 range.

Like other Pentax DSLRs, the K-x allows users to choose between the proprietary PEF and 'open' DNG raw file formats. It also provides three JPEG sizes and compression ratios. Raw files are only recorded at full image size and RAW+JPEG capture is supported for both raw file formats.

JPEG compression levels appear to be lower than in the K-m, providing larger files for the same resolutions. Typical file sizes are shown in the table below.

Like the K7, the K-x offers two continuous shooting speeds, albeit at a slightly slower frame rate. In the High-speed mode, the camera can record up to 17 high-resolution JPEGs or up to 11 raw shots at up to 4.7 frames/second. The Low-speed mode records at two frames/second and users can capture up to 11 raw frames in a burst or shoot high-resolution JPEGs until the memory card is full.

Like the K-m, the K-x provides two noise reduction processing settings, separately covering slow shutter speeds (long exposures) and high ISO settings. Both settings are found in the Custom Function menu and the default settings are on for the former and off for the latter. Slow shutter speed NR processing can only be switched on and off but high ISO NR processing offers four levels: off, weakest, weak and strong.

Live View and Video
These features are similar to the Pentax K7 and based on the K20D. Live View is accessed via a dedicated button, between the Quick Review and Info buttons on the rear panel. Contrast-detect autofocusing is the default AF system in Live View mode. It uses data from the image sensor and is relatively slow.

Face detection AF is also provided, using the contrast-detect system. Up to 16 human faces can be indentified and a white frame will appear on the monitor around each face, with the main face identified by a yellow frame. Focusing and exposure metering will prioritise the main face.

Selecting phase-difference AF cancels the Live View mode when the shutter button is half-pressed and focuses the camera with the dedicated AF sensor. It's faster and more accurate but the Live View display disappears momentarily, only reappearing when focus has been achieved.

Pressing the Info button in Live View mode, magnifies the image by two, four or six times for focus checking. Users can also display a data or grid overlay on the Live View or superimpose a small brightness histogram. The Electronic Level display can also be applied.

To shoot video, the mode dial must be set to the movie mode and Live View capture must be used. Recording starts and stops when the shutter button is pressed. Audio is recorded monaurally. Focus is fixed with the first frame, which means moving subjects can't be tracked and are likely to be unsharp if they approach the camera. The flash is also inactivated and sensitivity defaults to auto.

Like the K7, the K-x uses the AVI (Audio Video Interleave) format to record video clips with a frame rate of 30 fps. Two sizes are supported: 1280 x 720 pixels with a16:9 aspect ratio and 640 x 416 pixels in 4:3 aspect ratio. Three quality levels are provided for each. The table below shows typical capacities for a 4GB SDHC card.

Unlike the Nikon cameras, you can record for more than five minutes at a time. The camera can record video continuously for up to 25 minutes with a clip length limit of 4GB. Recording will stop when the memory card is full and the camera will save the recording. Depending on the clip length, this locks the camera for between about 20 seconds and more than a minute.

Although ISO is non-adjustable, setting Movie Aperture Control in the menu to Fixed lets you adjust aperture settings.  A warning will appear on the monitor if under- or over-exposure is detected.

Playback and Software
As  in the Pentax K7, options include one shot (with or without shooting data and/or colour channel histogram), index display (4, 9, 16, or 36 thumbnails), calendar filmstrip and folder playback. Images can be magnified up to 16x resized, cropped and rotated. Side-by-side comparison of two shots is also supported and raw files can be 'developed' in-camera and saved as separate JPEG or TIFF files.

Most of the digital filters provided for image capture can be applied in playback mode in the camera - along with a couple of additional filter effects that aren't supported for image capture. Many effects are adjustable, so users can fine-tune the ‘look' of the picture to suit their requirements. Adjusted images are saved as separate files. Some examples are shown below.


Examples of some of the Digital Filter effects that can be applied to images post-capture. From top left:  top row - original image, toy camera, retro; middle row - high contrast, watercolour, pastel; bottom row - fish eye, monochrome (with toning), soft focus.

Users can also apply DPOF tagging and protect or delete selected shots.  Movie playback is also supported with no data, basic data or full data displayed.

The software bundle consists of the latest versions of Pentax's Digital Camera Utility 4, which includes a raw-data processing application based on the previously-used Silkypix processing engine developed by Ichikawa Soft Laboratory plus a browser application. However, since no software was supplied with the review camera, we can make no further comments.

Performance
Pictures taken with the test camera were similar to the shots we took with the K-m. Contrast and saturation were restrained; out-of-camera sharpness was acceptable and colours were natural-looking. Autofocusing was acceptably fast and metering was accurate across a wide variety of subjects and with all metering modes.

Initially, power management appeared to be faulty, with the camera flattening a set of NiMH rechargeables in less than 30 shots. However, with several recharges of the batteries, we were finally able to get more than 150 shots per charge, which is less than 1/10 of the CIPA rating for this camera - but a significant improvement.

The body-integrated image stabiliser enabled us to use shutter speeds approximately two f-stops slower than would have been possible with a non-stabilised camera. More than 90% of shots taken in our stabiliser tests were sharp with this degree of adjustment.

Without a software disk, we had to conduct our resolution tests on DNG.RAW files, which were converted into 16-bit TIFF format with Adobe Camera Raw. Two main factors became evident in the course of our tests:
1. Resolution was strongly influenced by the choice of file format and only met the resolution expected for a 12-megapixel camera with raw files. The best JPEGs were slightly below expectations in resolution.
2. Resolution was dependent on focal length and aperture settings. Imatest revealed two distinct ‘sweet spots' in the lens's performance: at f/5.6 with the 45mm focal length and around f/9 for the 18mm focal length. Edge softening could be seen at all focal lengths throughout the aperture range. The graph below shows the results of our tests.

 Resolution remained relatively high throughout the test camera's sensitivity range with a surprisingly small difference revealed between the ISO 200 and ISO 12800 settings. The graph below shows the results of our Imatest tests and also highlights the difference between JPEG and raw performance.

Test shots taken in dim lighting with and without flash showed little visible noise right up to ISO 1600. Both pattern and colour noise could be seen in long exposures at ISO 12800 but shots were printable and little noise could be seen in snapshot-sized prints. Flash shots appeared slightly less noise-affected at ISO 12800 but were a little soft.

The built-in flash provided even illumination of an average-sized room throughout the camera's ISO range. Flash exposures were also well balanced for indoor close-ups for which flash provided the main illumination.

Barrel distortion was noticeable in shots taken with the 18mm focal length setting, although it was largely resolved by zooming in to 35mm. No pincushion distortion was evident at 55mm.

The lateral chromatic aberration we identified with the kit lens when we reviewed it with the K7 was also evident with the K-x body. Best results were obtained between 35mm and 55mm focal lengths, where CA remained in the ‘negligible' band. At 24mm CA was mainly in the ‘low' band, while at 18mm it moved well into the ‘moderate' category. In the graph below, the red vertical line represents the boundary between ‘negligible' and ‘low' while the green line separates ‘low' from ‘moderate' CA.

Video quality from the review camera was similar to clips we shot with Nikon's D90 and D5000 models. Picture quality was reasonably good with each resolution setting (although not outstanding); audio quality was pretty ordinary.

Clips often exhibited the so-called ‘jello effect' in which camera shake and horizontal movement of the camera to follow moving subjects produced wobbly videos. The lack of focus tracking further reduced picture quality.

You can avoid most of these problems by mounting the camera on a tripod before you start shooting video clips and by sticking with stationary subjects or slow-moving subjects that remain at the same distance from the camera. Switching on the body-integrated Shake Reduction system improved matters considerably - but not with faster-moving subjects.

The review camera powered up in just under 0.2 seconds and we measured an average capture lag of less than 0.1 seconds, which was eliminated by pre-focusing. It took 1.8 seconds, on average, to process each high-resolution JPEG, 2.2 seconds for each DNG.RAW, 2.3 seconds for each PEF.RAW file and 3.2 seconds for each RAW+JPEG pair. Shot-to-shot times averaged 0.32 seconds.

In the high-speed continuous shooting mode we recorded 10 high-resolution JPEG frames in two seconds, which is slightly faster than the claimed 4.7 frames/second speed. Shooting DNG.RAW files in burst mode we were able to record five frames in 0.9 seconds, while four RAW+JPEG pairs were recorded in 0.7 seconds before capture speeds slowed. It took 6.7 seconds to process the burst of JPEGs, 7.6 seconds for the raw files and 8.9 seconds for the RAW+JPEG pairs. The K-x can, therefore, support faster burst speeds at high resolution than either Canon's EOS 500D or the Nikon D5000.

Buy this camera if:
- You're seeking an affordable, feature-rich DSLR with some creative in-camera filter effects.
- You want a wide range of pre- and post-capture, in-camera image adjustments.
- You're happy to shoot and process raw files when high resolution output is required.
- You'd appreciate the Live View shooting capabilities.  
- You'd enjoy shooting the occasional video clip for viewing on a widescreen TV set. 
- You require superior high-ISO performance.

Don't buy this camera if:
- You want autofocusing while shooting video clips.
- You require fast autofocusing and focus tracking in Live View mode.
- You require a large buffer memory for continuous shooting.
- You're not interested in in-camera processing to obtain special effects with JPEG files.
- You'd like a wide choice of lenses (Pentax's range is currently smaller than competing brands).

IMATEST GRAPHS

JPEG image files

Raw image files converted into 16-bit TIFF format with Adobe Camera Raw.

SAMPLE IMAGES

Auto white balance with incandescent lighting.

Auto white balance with fluorescent lighting.

30-second exposure at ISO 200, 35mm focal length, f/5.6.

6-second exposure at ISO 6400, 35mm focal length f/9; no noise reduction.

6-second exposure at ISO 12800, 35mm focal length f/13; no noise reduction.


Flash exposure, ISO 200; 55mm focal length, 1/30 second at f/5.6.

Flash exposure, ISO 3200; 55mm focal length, 1/30 second at f/5.6.

Flash exposure, ISO 12800; 55mm focal length, 1/50 second at f/5.6

18mm focal length, ISO 200; 1/320 second at f/7.1.

55mm focal length, ISO 200; 1/400 second at f/8.


Coloured fringing with 18mm focal length; ISO 200, 1/500 second at f/8.

Crop from the above image, enlarged to 100% to show visible coloured fringing.

Rectilinear distortion at 18mm; ISO 200; 1/320 second at f/7.1.

Close-up taken with the Macro Scene mode at 55mm; ISO 200, 1/320 second at f/7.1.

Bokeh at wide apertures; 42.5mm; ISO 200; 1/640 second at f/7.1.

Image stabiliser test: 55mm focal length; ISO 400, 1/13 second at f/5.6; spot metering.

55mm focal length, ISO 200; 1/60 second at f/5.6.

Image sensor: 23.6 x 15.8mm CMOS sensor with 12.9 million photosites (12.4 megapixels effective)
A/D processing: 12 bits/channel
Lens mount: Pentax KAF2 bayonet for KAF3, KAF2, KAF and KA lenses
Focal length crop factor: 1.5x
Image formats: Stills - JPEG (Exif 2.21 with 3 compression levels), Raw (PEF/DNG), RAW+JPEG; Movies - AVI (Motion JPG)
Image Sizes: Stills - 4288 x 2428, 3936 x 2624, 3072 x 2048, 1728 x 1152; Movies - 1280 x 720, 640 x 480 (both at 24 fps)
Image Stabilisation: Sensor-shift Shake Reduction (4 stops max)
Dust removal: Image sensor movement combined with SP coating (Dust Alert available)
Shutter speed range: 30 to 1/6000 second plus Bulb
Exposure Compensation: +/- 3EV in 1/2 or 1/3 Ev steps
Exposure bracketing: 3 frames, up to +/- 1.5 (1/2 steps) or +/- 1.0 (1/3 steps)
Self-timer: 2 or 12 seconds delay
Focus system: TTL phase-matching SAFOX VIII  system with 11 AF points (9 cross type); AF assist via built-in flash
Focus modes: AF Auto, AF Single (w focus lock), AF Continuous (available in Action mode including Auto Picture Action, Kids, Pet, Stage Lighting, Night Snap, P/A/S/M/B/Sv), Manual Focus point adjustment: 11 point auto, 5 point auto, AF point select, centre/spot
Exposure metering: 16 segment TTL open aperture metering with Multi-segment, Centre-weighted and Spot modes 
Shooting modes:  Auto Picture, Picture (with Portrait, Landscape, Macro, Action, Night Scene Portrait, Flash Off), Scene (Night Scene, Surf & Snow, Food, Sunset, Kids, Pet, Candlelight, Museum, Night Snap [JPG]), Program, Sensitivity Priority, Shutter Priority, Aperture Priority, Metered Manual, Bulb (available in Metered Manual)
Picture Style/Control settings: Digital filters: Toy Camera, High Contrast, Soft, Starburst, Retro, Colour Extract (6), Fisheye, Custom (8) - all are adjustable
Colour space options: sRGB, Adobe RGB
Custom functions: 22
ISO range: Auto: ISO 200-6400 (in 1, 1/2, 1/3 EV steps); up to ISO 1600 in Bulb; expandable to ISO 12,800
White balance: Auto, Daylight, Shade, Cloudy, Fluorescent (D, N, W, L), Tungsten, Flash, CTE Manual mode; WB fine adjustment available in all modes
Flash: Retractable P-TTL auto/manual popup flash; GN 12 (m/ISO 100); On, off, redeye, slow sync, slow sync with redeye, slow sync with trailing curtain, wireless modes
Flash exposure adjustment: -2 to 1 EV (1/2 steps)
Sequence shooting: Max. 4.7 frames/second for 17 JPEG, 5 RAW 
Storage Media: SD/SDHC memory cards (single slot)
Viewfinder:  Pentamirror with approx. 96% coverage; 0.85x magnification, Natural-Bright-Matte II focusing screen; Dioptre adjustment:  -2.5 to 1.5 dpt
LCD monitor: 2.7-inch TFT colour LCD monitor with 230,000 dots
Live View: Yes with contrast, phase difference, and Face Detection AF (up to 16 faces)
Video Capture: Yes; 1280 x 720 or 640 x 480 at 24 fps
Data LCD: No
Playback functions: One Shot (no data, basic data, full data, colour channel histogram), Multi Image Display (4, 9, 16, or 36 thumbnails), Calendar Filmstrip, Folder, Magnification (quick zoom available), Select & Delete, Movie Playback (no data, basic data, full data), Bright/Dark Indication Mode palette: Image Rotation, Digital Filter, Resize, Cropping, Slideshow, Image Comparison, RAW Development, Index Print, Protect, DPOF Magnification: Up to 16x, scrollable; Digital filters (playback): Toy Camera, Retro, High Contrast, Extract Colour (6), Watercolour, Pastel, Miniature, Base Parameter Adj, Monochrome (filter effects, toning), Colour (6), Soft, Starburst, Fisheye, Slim, HDR, Custom Filter
Interface terminals: USB 2.0 Hi-Speed, AV out, Video out (NTSC/PAL); IR remote control
Power supply: 4x AA lithium, alkaline or NiMH rechargeable; CIPA rated for approx 1900 shots
Dimensions (wxhxd): 122.5 x 91.5 x 67.5 mm (body only)
Weight: 515 grams (body only)