Digital SLR

Pentax has designed its 14.6-megapixel K20D model to appeal to demanding photo enthusiasts but many of its features will also appeal to professional photographers. Like the earlier K10D model, the K20D is built to resist dust and moisture with seals protecting 74 different parts of the camera body. Physically the two cameras are similar, with identical body dimensions, although the new model has a larger LCD and is five grams heavier than its predecessor.

As with the K10D, the K20D's metal chassis is polycarbonate-clad. It's as well-balanced as its predecessor, with a large, but comfortable, grip that provides easy access to key shooting controls. The 2.7-inch monitor provides a worthwhile improvement but, otherwise the new model has a similar data LCD on the top panel and an identical set of controls on both top and rear panels. Both cameras record to SD or SDHC cards and the card and battery compartment doors lock very securely.

Front, back and top views of the K20D.

The body-integrated SR (Shake Reduction) mechanism is essentially identical to the system used in the K10D and relies on angular velocity sensors to detect camera shake. A ball-bearing-mounted oscillator unit with four electromagnets detects and counteracts motion by re-positioning the free-floating image sensor. Although the K20D's image sensor unit is lighter than its predecessor's and Pentax has refined the data-control algorithm to make the system more effective it still provides compensation of between 2.5 and four shutter speed steps with all existing Pentax interchangeable lenses.

The K20D supports the same shooting modes as its predecessor, with Program AE and manual exposure control plus priorities for aperture (Av), shutter speed (Tv), sensitivity (Sv) and a 'TAv' mode that lets photographers set both the aperture and shutter speed while the camera will adjust the ISO setting. ISO values are now included in the viewfinder display to assist users shooting in this mode. The standard Pentax 'green button' is provided for full-auto shooting and the same three-second Guide display appears each time you switch the camera on or change a mode to clarify current settings.

The recording mode menu.

It also includes the same 'USER' mode, which lets you retrieve exposure combinations you have saved via the Setup menu. Settings that can be adjusted in this mode include file format (covering raw file format and JPEG size and quality), colour space, exposure mode, flash mode, drive mode, exposure bracketing (steps and number of frames), sensitivity, auto sensitivity adjustment range, white balance and expanded dynamic range.

The Function button menu.

Another feature carried over from the K10D is the 'Fn' button, which accesses the drive, flash, white balance, sensitivity and Custom Image processing settings in the shooting mode or the DPOF, Digital Filter, slideshow and Raw display settings in playback. Hitting the Fn and OK buttons in playback mode displays two sequential shots side-by-side for comparison. This function is also available in Enlarged view, allowing focusing comparisons.

Sensor and Image Processing
Unlike the K10D, the K20D uses a CMOS image sensor, which is marginally smaller in area than the earlier chip. Measuring 23.4 x 15.6mm, it has a resolution of 14.6 megapixels (effective) and supports sensitivities up to ISO 6400 (up from ISO 1600), although this setting is only available via a custom function. We believe Samsung manufactured this imager as both companies collaborate on DSLR development and Pentax has no sensor foundry.

According to Pentax, the new chip - which was developed in collaboration with Samsung - boasts a higher ratio of imaging area to circuitry than previous Pentax imagers. Consequently, it also claims to be better at collecting light that enters the lens at an angle, although we have no way to validate this claim. We estimate the area of individual photosites to be approximately five microns square, which is smaller than the 6.01-micron square photosites on the K10D's imager.

On paper, the K20D appears to have the same image processor as its predecessor. It certainly has the same name (PRIME) and also includes DDR2 (Double Data Rate 2) RAM components to ensure fast data processing and file transfer. Digital noise reduction processing has also been improved, a necessity for higher sensitivity settings.  

The new camera claims a full-resolution continuous shooting speed of up to three frames/second for 14-16 RAW files or 38 JPEGs. The frame rate is identical to the K10D's, which is impressive given the larger file sizes. The buffer also appears to be larger as raw file capacity is increased by roughly 50%. A new high-speed burst mode can record 1.6M JPEGs at approx. 21 fps with a maximum capacity of up to 115 frames. 1.6M JPEGs.

Like the K10D, the new model records image files in the standard JPEG format as well as Pentax's proprietary PEF.RAW and the open-format DNG file formats. Typical file sizes for each of the image size and quality settings are shown in the table below. 

The in-camera raw file converter has been replaced with a new 14-bit ADC converter. Although this may seem like a backward step (the K10D boasted a 22-bit converter), the previous model only offered 10-bit file conversion in practice, so it's actually an improvement. The K20D also has a new pixel mapping function for detecting defective pixels in the sensor. 'Dead' pixels are removed from images by interpolation.

Live Viewing
The K20D's new Live View function is engaged by moving the main power switch past the On position to a circular, iris-like icon. This raises the mirror and displays the scene on the 2.7-inch LCD screen, allowing photographers to preview the shot.  Live View previews can be displayed for up to three minutes before the mirror drops.

The autofocusing system disengages when Live View is used so if you try to half-press the shutter button a picture will be recorded. You can focus manually with the lens focusing ring or, if you wish to use autofocus, you must hold the AF button down. This causes the mirror to drops so the AF system can operate but, in the process, blanks out the live view. When it rises again several seconds later, the subject should be in focus.

This option is only usable when the camera is tripod-mounted as any variation in the camera's position between pressing the AF button and taking the shot will cause accurate focus to be lost. The only way of confirming focus when the LCD blacks out is when the noise of the AF motor ceases.

In Live View mode, the displayed image can be magnified up to 8x by turning the e-dial on the rear panel for focus checking. The effectiveness of the in-camera shake reduction function can also be confirmed in the on-screen view. In fact, apart from autofocusing, shooting with Live View is like shooting with a digicam.

Digital Preview options.

The Digital Preview section in the playback menu can be used to superimpose a framing grid and/or AF on the Live View screen (Neither is displayed by default.)  It also allows a bright/dark area warning and/or histogram (brightness or RGB) to be displayed with the preview when you press the Info button.

If you press the Fn button when Digital Preview is engaged you can save the preview image as a JPEG file by pressing the OK button when the confirmation screen appears. These previews are captured and saved with the resolution you have selected in the camera's menu.

New Functions
Although the K20D also has the same dedicated RAW button as its predecessor (which defaults to a single raw shot), if you want to shoot RAW+JPEG files it's now easy to select this mode in the File Format section in the main menu. It's no longer only accessible via a Custom Function.

In-camera Raw file processing now allows Raw files to be converted into JPEG or TIFF format instead of JPEG only. JPEG size and quality parameters are still adjustable and the same adjustments to white balance, sensitivity, image tone, saturation, sharpness and contrast are provided. However, colour space settings can now be changed. Four levels of high-ISO noise reduction processing are also provided.

Interval shooting of up to 99 frames over a 24-hour period is also provided in the Recording Mode menu and you can set the time for the first picture in the sequence to be taken as well as the intervals between shots. A new multiple exposure mode has also been added, allowing you to superimpose up to nine shots. Automatic exposure compensation can be applied based on the number of frames.

A couple of new Custom Functions have been added, bringing the total to 36. A new 'Expand Sensitivity' setting lets you increase the upper sensitivity limit to ISO 6400. There's also a new 'One-Push Bracketing' setting that sets the camera to shoot all frames with one release when using exposure bracketing. Another new function locks in automatic fine-tuning of white balance when specifying the light source in the white balance setting.

Two Custom Functions are now provided for noise reduction, with high-ISO and slow shutter speed processing separately adjustable. The colour space setting has been moved from the Custom menu to the main menu and colour temperature adjustment in Mired steps has been deleted, leaving only Kelvin steps. Adjustments for E-dials in B and X modes have been added.

A new Flash in Wireless Mode adjustment sets the built-in flash discharge method in wireless mode. Another new Display Sensitivity setting sets whether to switch the number of recordable images in the LCD panel and viewfinder to over-ride the sensitivity display. Catch-in focus is another new function that releases the shutter when a subject comes into focus when a manual lens is fitted to the camera. AF adjustment is also provided in the new Custom Function suite. 

The new model provides some minor handling improvements for photographers, in part because it is a quieter camera to operate. Both the mirror and shutter mechanism are better dampened and autofocusing noise is also subdued. Shake reduction is also marginally improved.

A nice addition is the new Dust Alert function, which detects any dust particles that remain on the sensor and visually displays where they are to make them easy to remove. The system is rather nifty; after locating the dust spots, the camera displays them on the LCD with a reversed view that is surrounded by a graphic of the lens mount. This makes it easy to track down spots for removal with a blower, cotton bud or cleaning pad.

Playback
Most of the standard playback modes are provided, including single and multi-image index displays, slideshows and image plus histogram or highlight/shadow alert. Each time the Info button is pressed, the display toggles through four display options: standard display (with basic information), histogram display, detailed display and image only.

The playback menu.

Users can choose between brightness and RGB histograms, with the latter also providing a small brightness graph in addition to the graphs for the colour channels. Slideshow intervals can be set to display images at any of four time intervals: three, five, ten or 30 seconds.

The Standard playback mode with brief data display.

Playback with histogram.

Detailed shooting data display.

Selected images can be rotated or protected and users can delete all images, erase individual shots of delete selected images in a multi-image index display. Entire folders can also be deleted.

A video cable is provided for displaying shots from the camera on a standard TV set (PAL or NTSC) but high-definition playback does not appear to be supported and the camera lacks a widescreen capture mode.

Software
The Pentax Digital Camera Utility disk supplied with the K20D has two applications: Pentax Photo Browser and Pentax Photo Laboratory, an evolution of the  Silkypix application bundled with the K10D. The browser is a straightforward file browser that is similar to the browser applications provided with most DSLRs. It displays folder trees, thumbnails of files and image metadata and provides a direct link to the 'laboratory' application.

 
Browser display with metadata.

Browser display with Auto Image Fix options.

Pentax Photo Laboratory appears to be designed mainly for automated raw file processing but, if you dig a little, you can find a wide range of image adjustments. Selecting the Custom Processing option from the drop-down menu will reveal them. The illustrations below show the style and content of the processing interface.

 
Raw file processing adjustments in Pentax Photo Laboratory.

Cropping in Pentax Photo Laboratory.

Interestingly, although Pentax Photo Laboratory opened PEF.RAW files quickly and easily, we were unable to open DNG files. This isn't a problem because, being a 'universal' file format, DNG files can be opened in just about any independent raw file processor. We obtained excellent results with Adobe Camera Raw 4.3.1.31 and Photoshop CS3.

 
Processing DNG raw files in Adobe Camera Raw.

Performance
The review camera was supplied with the smc Pentax-DA 1:3.5-5.6 18-55mm AL lens, which covers a slightly wider field of view than the Pentax lens we used for reviewing the K10D. Subjective assessment of pictures taken with the camera-plus-lens combination showed exposure metering to be slightly biased towards recording highlight details so shots were a little darker than shots from the K10D. However, they contained plenty of detail and showed no evidence of over-sharpening. We observed a slight yellow-brown cast in many shots, which was picked up in our Imatest testing.

Imatest showed resolution to be slightly lower than expectations, although still relatively high - and quantifiably higher than the K10D. It also showed a close correspondence between centre and edge resolution, indicating good flatness of field and negligible corner darkening in the lens. A graph showing the results of our Imatest tests at different focal lengths and aperture settings is provided below.

Resolution remained high at all ISO settings up to (and including) ISO 1600 but declined sharply thereafter. The graph below plots the results of our Imatest tests. Image noise became visible at ISO 1600 when shots were enlarged to 100% but was increasingly obvious as sensitivity was increased.

Colour accuracy was reasonably good but Imatest detected some shifts in green and purple hues and slightly increased red saturation. Skin tones were also slightly off the mark and their saturation was a tad high. Lateral chromatic aberration was consistently low but we found traces of coloured fringing at the edges of some outdoor shots when they were enlarged to 100%.

The auto white balance setting delivered neutral colours with fluorescent lights but failed to remove the orange cast of incandescent lighting. This residual orange cast was easily removed with white balance tuning in the camera- and also with editing software and through raw file processing. Better performance was delivered by the tungsten pre-set and close to neutral colours with the manual measurement function.

The pop-up flash performed as well as the flash on the K10D and provided good and even exposures throughout the test camera's ISO range. Long exposures at night were relatively free of colour noise up to ISO 800 but noise increased visibly thereafter. At ISO 6400, noise was quite obvious, although no stuck pixels were found.

The camera powered-up almost instantaneously. However, swapping to Live View mode incurred a delay of just over one second. When shooting with the viewfinder, we measured an average capture lag of 0.2 seconds, which reduced to instantaneous capture with pre-focusing. With Live View, capture lag increased significantly. The table below compares the results we've obtained when testing the live viewing lags of several popular DSLRs.

Task	Pentax K20D	Sony A350	Canon EOS 40D	Olympus E-410
Capture lag (without pre-focusing)	0.7 sec.	negligible	0.13 sec.	0.7 sec.
Shutter lag (pre-focused)	n.a.	negligible	0.1 sec	0.55 sec.
Time to process Large/Fine JPEG	2.0 sec	2.8 sec	3.1 sec.	6.1 sec.
Time to process burst of 10 Large/Fine JPEGs	4.5 sec.	4.1 sec	4.4 sec.	6.8 sec.

We also measured the following write speed times with a range of popular SD and SDHC memory cards.

File Format	ATP Pro Max SDHC 4GB	Verbatim Premium SDHC 4GB	Panasonic Pro High Speed SD 1GB	Verbatim SD 1GB
PEF.RAW	16.11MB/sec	9.76MB/sec	15.86MB/sec	4.28MB/sec
JPEG (high res.)	16.70MB/sec	10.57MB/sec	15.99MB/sec	4.93MB/sec

IMATEST GRAPHS

Centre of field resolution.

Edge of field resolution.

SAMPLE IMAGES

Auto white balance with incandescent lighting.

Auto white balance with fluorescent lighting.

Close-up.

Backlighting and flare.

18mm focal length, 1/180 second at f/5.6, ISO 200.

Lens at 55mm focal length, 1/180 second at f/6.7, ISO 200.

30-second exposure at ISO 200.

20-second exposure at ISO 6400.

Image sensor: 23.4 x 15.6 mm CMOS with approx. 15.07 million photosites (14.6 megapixels effective)
Lens mount: Pentax KAF
Focal length crop factor: 1.5x
Image formats: JPEG (4 quality levels), RAW (PEF+DNG)
Image Sizes: 4672 x 3104, 3872 x 2592, 1824 x 1216
Image Stabilisation: Yes (in body)
Dust removal: Vibration of optical low pass filter in front of sensor; Dust Alert displays location of dust spots
Shutter speed range: 30-1/4000 second plus Bulb
Exposure Compensation: +/- 3EV in ½ EV steps or +/- 2EV in 1/3 EV steps
Self-timer: 2 or 12 second delay
Focus system: TTL phase-matching system (SAFOX VIII) with 11 AF sensor points
Focus modes: Single-servo AF, continuous-servo AF, manual focusing
Exposure metering: 16-segment TTL multi, centre-weighted  and spot metering
Shooting modes: Auto (‘Green mode’), P (‘Hyper-program’), Sv (sensitivity priority), Tv, Av, TAv (shutter & aperture priority), M (‘Hyper-manual’), Bulb, X (flash X-synch)
Picture Style/Control settings: Image Tone (6 pre-sets), Saturation/Filter Effect, Hue Toning, Contrast, Sharpness
Colour space options: sRGB, Adobe RGB
Custom functions: 36
ISO range: Auto, ISO 100-3200 in 1, ½ or 1/3 EV steps; ISO 6400 available via Custom Function
White balance: Auto, daylight, shade, cloudy, fluorescent light (x3), tungsten light, flash, manual, colour temperature (3 types); fine tuning available
Flash: P-TTL flash with serial control; GN approx. 13 (ISO 100/m); synch speed at 1/180 sec.; daylight and slow-speed synch
Flash exposure adjustment: -2.0 to +1.0 EV in 1/2EV or 1/3EV increments
Sequence shooting: Up to 3 fps for 14-16 RAW, 38 JPEG; High-speed burst at approx. 21 fps for 1.6M JPEGs (up to 115 frames)
Storage Media: SD/SDHC  cards
Viewfinder:  Pentaprism with interchangeable Natural Bright Matte II focusing screen; approx 95% field of view; magnification approx 0.95x (with 50mm f/1.4 lens); Diopter adjustment -2.5 to +1.5 dpt
LCD monitor: 16-segment TTL metering;
Live View modes: Optical preview with depth-of-field confirmation (electronically controlled and usable in all exposure modes); Digital preview with composition, exposure, focus and white balance confirmation
Data LCD: Yes; displays full photographic and digital settings
Playback functions: Full frame, thumbnail (4, 9 or 16 segment index), zoom (up to 32x with scrolling), image comparison, folder display, slideshow, brightness/RGB histogram, shooting data, bright/dark area indicators, image rotation
Interface terminals: USB 2.0 Hi-Speed, Video (PAL/NTSC), DC-in, cable switch terminal, X-synch socket
Power supply: D-LI50 rechargeable lithium-ion battery (740 shots/charge (without flash)
Dimensions (wxhxd): 141.5 x 101 x 70 mm (body only)
Weight: 715 grams (body only)