Pentax K-50: Performance

by Jim Keenan Reads (66)
Editor's Rating

TG Ratings Breakdown

    • Image/Video Quality
    • 8
    • Features
    • 8
    • Design / Ease of Use
    • 8
    • Performance
    • 9
    • Expandability
    • 9
    • Total Score:
    • 8.40
    • Rating 1 to 10, top score 10

Shooting Performance

With the K-50 sharing most the specifications of its predecessor I was curious to see if the new camera would differentiate itself at all from what was, after all, a very capable platform with the K-30.

The K-50 started up in about the same time as the K-30, taking just under one second to present a display on the monitor. There is a dust removal feature that can be enabled at startup, shutdown, or both – enabling this feature at startup adds about 1/5 of a second before the display comes up. With my eye affixed to the viewfinder at power up I was able to acquire focus and get off a first shot in about 1.5 seconds. After that, single shot to shot times take only as long as required to reacquire focus and press the shutter again.

The K-50 retains the one push file format shooting option I first encountered in the K-30. The default setting for the RAW/Fx button located on the left side of the camera body permits the conversion of single JPEG images into a RAW file at the time they are captured. When shooting single JPEGs, the K-50 saves the RAW data for the JPEG on a separate buffer; before you take the next shot if you decide the image would better serve your purposes as a RAW image, you can change it. Simply display the last image via the playback button and check to see if an icon depicting the exposure compensation button along with the word RAW and an icon depicting the memory card appear in the upper right corner of the replayed image — if they do, push the exposure compensation button atop the camera body and you will be prompted on the monitor about saving the JPEG as a RAW file. You can use the button customization submenu in the record menu to disable this feature if you wish, or assign other functions to the RAW/Fx button.

An optional GPS unit may be attached to the K-50 and provides features such as an electronic compass, GPS time sync and astrotracer. This latter feature matches the movement of the camera’s shake reduction unit with the movement of celestial bodies during time exposures, allowing the capture of objects such as stars as individual points rather than trails.

Pentax advertises a continuous shooting rate of approximately 6 frames per second for 30 JPEG or 8 RAW files: our review unit flew well past the 30 JPEG figure and captured 9 RAW images with the camera at default settings before shooting speed slackened. (Memory media was a Lexar 32GB/600x SDHC card). Shooting a RAW plus JPEG file format produced 7 captures before things slowed. Write times for a 30 shot sequence of JPEG files was about 5 seconds; 9 RAW images wrote in about 4 seconds and 7 RAW/JPEG captures took almost 6 seconds.

The K-50 comes with a default setting of “focus priority” for both single and continuous autofocus settings, which means that the camera won’t allow the shutter to be fired unless an image is in focus. There may be occasions, particularly when tracking a moving subject in continuous AF mode where the shooting rate drops below the advertised 6 fps as the camera acquires focus. The K-50 also allows you to set “FPS priority” which favors the continuous shooting rate over focus. Focus priority has been the setting of choice in my personal cameras for years, operating on the theory that when shooting continuous bursts it’s better to get some sharp images out of the sequence at perhaps less than advertised shooting rates rather than a full speed sequence of fuzzy images.

The camera also features a “distortion correction” setting that is disabled as a default setting; enabling this feature can help correct instances of barrel or pincushion distortion in captured images, but takes a heavy toll on continuous shooting performance. For example, with distortion correction enabled the K-50 managed only 7 JPEG images at the continuous high-speed shooting setting before slowing.

Autofocus performance in the K-50 seemed on a par with the K-30 and in any event comparable to other cameras in the similar market niche. AF generally acquired promptly in good lighting conditions and predictably was a bit slower in dim light; as with the K-30 the autofocus assist lamp seemed somewhat limited in its range. The default auto focus setting is a 5-point automatic mode with the camera selecting the active focus point; an 11 point automatic and user-defined 11 point and center point only options may be selected instead. There is a face detection and tracking AF option available in live view, which uses a contrast detection system in lieu of the TTL phase-matching autofocus system employed by the viewfinder. Live view was a bit slower to acquire focus than the viewfinder but was still fairly prompt in good lighting conditions and not too bad in dim light, assuming the focus assist lamp was capable of illuminating the intended subject.

The built-in flash on the K-50 is rated by Pentax for a guide number of about 39.3 feet (12 meters) at 100 ISO. This translates into a maximum aperture range of about 11.2 feet at wide-angle and 7 feet at telephoto. Available flash modes are dependent upon the shooting mode being employed and include auto, auto/redeye reduction, flash on, flash on/redeye reduction, slow speed sync, slow speed sync/redeye, trailing curtain sync as well as a wireless mode to synchronize an optional external flash without using a sync cord. Flash recycle times with a fully charged battery were quick, about 2 seconds in most cases and about 3 seconds when the flash fully discharged. Flash sync speed is 1/180 of a second.

Pentax lists the battery life for the rechargeable lithium-ion battery supplied with the K-50 as approximately 410 images with 50% flash usage and 480 images with no flash usage. AA lithium batteries provide 710 images with 50% flash usage and 1250 images without; the K-30 reported AA performance as 1000 images with 50% flash usage and 1600 without.

Lens Performance
The SMC Pentax-DA L 18-55mm F3.5-5.6 AL WR kit lens provided with our K-50 is a compact, standard zoom lens with focal lengths from 27.5mm to 84.5mm (in 35mm equivalents) owing to the physical dimensions of the camera sensor. Its optical design includes aspherical lens elements and super-low dispersion glass elements encased in a composite body and lens mount to save weight. While the lens itself has been in the Pentax arsenal for number of years, our review unit is a recent variant including weather sealing to complement the K-50’s sealed body.

Site editor Laura Hicks did a preliminary image quality shoot with the K-50 before sending it along to me and found disappointing image quality out of the kit lens at maximum aperture and the 55mm focal length. Things improved as the lens was stopped down from its maximum aperture but Laura nevertheless red flagged kit lens image quality for closer scrutiny in my time with the camera.

With default settings in the camera I shot the lens at 55mm in aperture priority mode and wide open at f/5.6 and got the same results reported by Laura – images looked really soft. Next, I closed the lens down a stop to f/8 in addition to going into the custom image menu and maximizing out the sharpness setting for the picture style I was using. Image quality was much improved as to sharpness and very usable directly out of the camera. Here’s an example of a default shot with the lens wide open and then again closed down to f8 with the picture style sharpness setting maximized.

Next, I took a look at the lens at wide-angle with maximum aperture and the bad news here is the 18-55 is even softer than it was at telephoto. The good news is repeating the process of maxing out picture style sharpness and closing the lens down a stop brings sharpness back to a satisfactory level. It’s not unusual for a lens to perform a bit better in the sharpness department when closed down from its maximum aperture, so the K-50/18-55mm kit lens combo isn’t breaking any new ground in this regard, but if you’re looking for maximum optical performance out of this setup utilize shooting modes that let you set the lens aperture at something other than wide open. The K-50 camera is compatible with every Pentax lens ever made: all K mount lenses install directly on the camera while the earlier screw mount and 647or 67 series lenses require adapters, so there’s a wide variety of higher performance lenses available for folks who want to move beyond the kit lens.

At the telephoto end and closed down 1 stop to f/8 the 18-55 is fairly sharp in the center with some slight softening in the corners and edges; wide open the lens is distinctly softer. At wide-angle closed down to f/5.6 the lens is fairly sharp in the center with a bit more softening in the corners and edges than at telephoto; wide open the lens is distinctly softer with some noticeable light drop-off in the corners. There is a bit of barrel distortion at wide-angle and a bit of pincushion at telephoto; both of these defects are prominent enough to be noticeable in images with straight lines on/near the perimeters of the frame, and both are handled nicely by enabling the “distortion correction” setting in the lens correction submenu on page 2 of the record menu. But, as mentioned earlier, enabling distortion correction hamstrings the continuous shooting performance of the K-50.

There is some longitudinal chromatic aberration (purple fringing) present at both the wide and telephoto ends of the 18-55 lens although enlargements in the range of 300% are necessary to make the defects readily visible — the lens actually does pretty well in this regard. The K-50 has a lateral chromatic aberration correction feature that is enabled by default but, as expected, there was no noticeable change in purple fringing with the feature enabled or disabled.

Video Quality
With virtually identical specifications to the K-30 it was no surprise the K-50 video shares the highs and lows of the video performance of its predecessor. On the plus side image quality is pretty good and full 1080 HD video can be recorded at 30, 25 or 24 fps. Even with its CMOS sensor the K-50 turns in a pretty credible performance in dealing with rolling shutter effect, which tends to stand out only when pans become exaggeratedly fast. On the negative side the microphone is wind sensitive and there is no wind cut feature; continuous autofocus in video capture is not available although autofocus on demand is — to refocus you press the AF button on the right rear of the camera body and then wait several seconds while the camera hunts back and forth before reacquiring focus, all the while recording the clunking sounds of the focus process. It takes about 3 seconds plus for the camera to switch into video capture mode after setting the mode dial for video capture, at which point the shutter button is used to acquire focus and initiate the start of video capture. While Pentax advertises video capture times of 25 minutes this time is achieved at less than maximum quality; full HD video at the highest image quality setting is good for about 16.5 minutes, assuming the 4GB maximum file size and/or circuit overheating doesn’t cut this short.

Image Quality
We covered a lot of ground on still image quality in discussing the optical performance of the 18-55 kit lens that came with our K-50 review unit, but suffice it to say that even default shots with the kit lens at maximum aperture might be acceptable if viewed at small size. The image softness problem becomes more readily apparent when images are enlarged to 100%. Closing down the lens a stop and ramping up the sharpness setting of the picture style being utilized (when possible) goes a long way toward producing nice images right out of the camera. But, like the K-30, the K-50 he has one last trick in the bag to produce a little extra sharpening in the camera. While the four-way controller allows the user to establish various degrees of sharpening within the individual picture styles, rotating the rear control dial toggles these settings between “sharpness” and “fine sharpness”; fine sharpness provides an additional level of sharpening. The following 2 shots were made at 55mm with the lens after closed down 1 stop to f/8 and the sharpening setting of the picture style set to maximum. The first shot was made with the sharpness setting, the second with fine sharpness.

Color reproduction out of the K-50 at the default “bright” picture style was pleasant, if a bit oversaturated – “natural” is a more accurate setting. The camera features 11 picture style options, same as the K-30, and here’s a look at the bright, natural, landscape, radiant, vibrant and monochrome versions. When shooting monochrome you have the option to employ green, yellow, orange, red, gentle, blue, cyan or infrared digital filters; the monochrome sample has the red filter enabled.

BRIGHT                                                                          NATURAL

LANDSCAPE                                                                    RADIANT

VIBRANT                                                               BW-RED FILTER

The K-50 has additional features such as digital filter and HDR capture but these options are only available when shooting JPEG files. K-50 RAW files were recognized by my Photo Ninja and Photoshop Camera RAW 6.7 converters, so I didn’t have to resort to the Pentax-supplied CD ROM for processing. Personally, the bulk of my shooting these days is done in RAW files simply because post processing is an easier and more rewarding task with a RAW file if the original shot isn’t perfect in terms of exposure. Here’s a shot that was taken as a RAW/JPEG combo – if you look closely at the JPEG version which is just as it came from the camera there are lost highlights in the petals of the cactus flower. The RAW version was post processed in Photo Ninja to recover the lost highlights and ramped up some color saturation in the process.

Auto white balance was used for the overwhelming majority of images taken for this review and did a good job and overall lighting conditions ranging from bright daylight to flash, open shade and overcast. In addition to the automatic preset there are daylight, shade, cloudy, 4 fluorescent options, tungsten, flash, and CTE (color temperature enhancement) presets along with 3 manual white balance options and a Kelvin temperature scale ranging from 2500 to 10000 in 100 degree increments.

Multi segment metering is the default exposure calculation method but there are center weighted and spot metering options available. Multi segment is considered the best choice for a variety of lighting conditions but can, on occasion, lose highlights in situations involving a fair amount of contrast.

While the K-50 utilizes a sensor and processing engine found in the K-30, both have the benefit of an additional year of engineering behind them and this is perhaps best indicated by the K-50 picking up an additional ISO sensitivity step, 51200.

ISO 100                                                                              ISO 200

ISO 400                                                                              ISO 800

ISO 1600                                                                              ISO 3200

ISO 6400                                                                              ISO 12800

ISO 25600                                                                              ISO 52100

100 and 200 ISO in the K-50 are indistinguishable and I shot most of the images for this review at 200 ISO to pick up an extra stop of shutter speed. The 18-55 kit lens is relatively slow to begin with and given its optical performance at maximum aperture you lose another stop closing it down to pick up some extra sharpness. 400 ISO is practically indistinguishable from the lower sensitivities although at 100% enlargement very close scrutiny shows a few miniscule artifacts here and there. 800 ISO is very similar to 400 ISO and at this point I have no reservations about shooting any of the sensitivities up to 800 for large print work. The jump from 800 to 1600 shows the largest change between any consecutive steps to this point, and this change is miniscule it best – a slight increase in grain readily apparent only upon very close inspection. As with the K-30, I think 1600 is a viable large print setting if there was no way to capture the image at a lower ISO sensitivity. There is a very definite increase in graininess going from 1600 to 3200 and while the image still looks good when viewed small, 100% enlargement shows a definite escalation of grain. 6400 is another magnitude grainier than 3200, losing more and more detail although color fidelity is remaining pretty good. 12800 deteriorates to about the same degree as 6400 did over 3200, with noticeably increased graininess and loss of detail, but still relatively true color fidelity. 25600 adds another heavy increase in graininess accompanied by a loss of detail and for the first time colors are noticeably blotchy at 100% enlargement. 51200 increases graininess and loss of detail by all another magnitude over 25600, and actually the term “graininess” to describe noise at 51200 should probably read something more like “small rocks”.

Overall, my general impression is that the K-50 offers up ISO noise performance very much on a par with the K-30.

Additional Sample Images


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