Pentax K-x at a glance:
- 12.4-million-pixel CMOS sensor
- HD video capture
- 4.7fps shooting rate
- Street price around £550,
including 18-55mm lens
Pentax K-x – Introduction
Although the Pentax K-x is based on the same design as the K-m, it actually inherits a number of features from the high-end enthusiast-level K-7. These include an 11-point AF system, in-camera HDR and HD video capture.
When we reviewed the Pentax K-m in AP 6 December 2008, we awarded it a score of 75%. While this is a good score, it lost some marks because we felt its performance lagged behind that of other entry-level cameras. Hopefully, Pentax will have made improvements in these areas rather than simply adding a few new ‘glamour’ features to appeal to the entry-level photographer.
While the K-x looks remarkably similar to the Pentax K-m, a number of changes have taken place inside the newer model. The first, and possibly most important, is that the sensor has been upgraded from a 10.2-million-pixel CCD sensor to a 12.7 million-pixel CMOS sensor. This small increase in resolution keeps it ahead of the resolution of the Nikon D3000, Canon EOS 1000D and Olympus E-450, which all feature ten-million-pixel sensors.
The switch to a CMOS sensor from CCD is presumably to allow HD video capture and Live View technology on the K-x. Another improvement that will have an impact on photographers is the new AF system. Instead of the rather basic five-point AF system, the K-x has the same 11 points found on the K-7.
Also inherited from the K-7 is the latest Prime II image-processing engine. This should have an impact on image processing and the speed of data transfer. In turn, Pentax has been able to increase the shooting rate in the K-x to an impressive 4.7 images per second.
A number of new in-camera image effects have been added to the K-x. A selection of cross-processing filters are available, but the most notable feature is in-camera HDR image capture. This creates a single in-camera HDR image by combining three different camera exposures. It is a feature I recently looked at in detail as a Feature in use when I reviewed the Pentax K-7 against the Nikon D300S (AP 17 October).
So while the Pentax K-x may have inherited its camera body from the K-m, there are a number of changes that have taken place inside the camera that should produce marked improvements in the K-x.
Build and handling
Like the K-m, the Pentax K-x is one of the smallest and lightest DSLRs available. Despite its size, the depth of the handgrip makes it comfortable to hold. It is also possible to use the camera single-handed and still change the shutter speed and aperture settings.
The rear of the K-x has the usual selection of shortcut buttons to alter the most regularly used settings. In addition, there is a green function button to which the user can assign one of the features they use the most. Pressing the Info button shows an extended shooting menu on the rear screen, which changes other features such as the picture mode, image file format, metering, AF modes and the HDR shooting feature.
Using the camera’s more in-depth menus is also straightforward, with most features appropriately named and easy to find. There are 22 different items in the custom menu. These can adjust a host of settings, ranging from the order of the auto bracketing to activating the expanded ISO sensitivity settings.
Although there are a huge number of settings, there is also a range of automated scene modes to help those learning photography to get good results. Apart from the addition of a dedicated Live View button and the opportunities that Live View offers, the Pentax K-x handles in a similar way to the K-m.
White balance and colour
When used in a variety of lighting conditions, I found that the Pentax K-x performed extremely well in AWB mode and in its default WB settings. There are also a large number of colour options and effects. These include the usual standard presets, such as landscape, portrait, vibrant and black & white, and each of these can be tweaked to the photographer’s taste. However, these settings are only part of the story.
There are seven filter effects, ranging from Toy Camera to a Fisheye effect, and a custom filter that allows you to create your own look. The effects are applied immediately after the image has been taken and they take a few seconds to process, so using the filters can slow down the camera’s shooting rate significantly. A better option is to apply the filters by editing the image in-camera later.
However, the fun doesn’t stop there. Among the new features of the K-x is the Cross Processing-style option. This applies one of four randomly selected cross-processing effects to an image. While it is intriguing to see which random effect will be applied, it can be frustrating if you don’t get the effect you like. This is compounded by the fact that in the pre-production model I had previously used, you could choose which style to apply.
With the K-x also including in-camera HDR creation from three individual exposures, there is a huge amount of creativity possible in-camera.
Image: The Cross Processing option has randomly added green and magenta hues to this image
The metering system of the Pentax K-x is the same 16-segment system found in the Pentax K-m and the K20D, but is not as advanced as the 77-segment system of the K-7.The K-x’s evaluative metering produces good results in most situations. Like all such systems, there are times when a bright sky or very dark foreground can fool the camera. In such cases, I found that using the AE-L button and spot metering mode helped to get more accurate results.
Like other Pentax DSLR cameras I have tested, I found that the K-x had a tendency to underexpose slightly. Switching to spot metering mode and taking an image of a grey card confirmed this. The measured value of the midtone was around 118 rather than 128. This was easily resolved by setting the EV compensation to +0.3EV
As mentioned earlier in this article, autofocus is one area where Pentax has made improvements with the launch of the K-x. The new model has an 11-point AF sensor, which is the same as that found in the K-7, and much improved over the five-point system of the K-m. Nine of these sensors are of the cross type, which are more accurate than standard AF points.
The biggest improvement in the AF is that the AF points can now be selected individually. However, the AF point in use is not illuminated in the viewfinder, which can make it difficult to remember which point is in use and where it is placed in relation to the subject on which you are trying to focus.
On the whole, the AF system of the K-x seems slightly faster than the AF of the K-m. I found that the K-x still searches for focus a little too much when in AF-C mode and it isn’t as ‘snappy’ as more expensive cameras.
That said, unless you intend to photograph sports or fast-moving wildlife, the AF should be able to cope adequately with most situations.
Resolution, noise and sensitivity
The 12.4-million-pixel sensor of the K-x doesn’t perform quite as well as other 12-million-pixel cameras we have tested. However, at ISO 100 it reaches 22 on our chart, which is better than the Pentax K-m.
Colour noise is well controlled in-camera at all ISO sensitivities. Looking at unedited raw files produced by the K-x, colour noise starts to appear at around ISO 400 but it only becomes a real problem at ISO 1600.
Even at ISO 12,800 both colour and luminance noise can be controlled in Adobe Camera Raw and it produces very good results given the ISO sensitivity. Pentax has obviously spent some time making sure that images are usable throughout the ISO range Although Pentax is clearly pushing the limits of what the 12.4-million-pixel sensor can do, the company has made it clear that the ISO 12,800 is an extended option, and not a default.
These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, still-life scene and a grey card. We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera’s detail resolution is at the specified sensitivity setting.
The section of the still-life image contains the emblem on a standard-sized matchbox. The full scene can be viewed at https://tinyurl.com/67sj96. Images are taken using the Sigma 105mm f/2.8 EX DG Macro lens.
Our tests show that the Pentax K-x has a dynamic range of around 12EV. This is a good score and matches many other more expensive cameras. In use, though, I found that the lower midtones are a little dark. However there is an in-camera solution.
Like most other digital SLRs, the K-x has highlight and shadow correction features. These do not affect the dynamic range, but they do reduce the brightness of highlight areas and lift shadows.
If you are taking images that you don’t wish to spend too much time editing before printing, it may be worth leaving these settings turned on. However, the shadow correction can introduce noise in shadow areas, so I would recommend using it only at low ISO sensitivities.
Viewfinder, LCD, Live View and Video
Unlike its predecessor, the K-m, the Pentax K-x features Live View technology. In my review of the K-m I commented that Pentax ‘may have missed a trick by not including a Live View mode’, so it is good to see it included on the K-x.
The Live View image is displayed on a 2.7in, 230,000-dot screen, which is the same as that on the K-m. While not up to the standard of the current 3in screens found on higher-end models, it shows enough detail to check that focusing is accurate.
Although Live View is now a standard feature, most photographs will still be framed using the optical viewfinder. This has a coverage of 96% of the final image, which is again on a par with other similar cameras in this price range. Viewfinder magnification is 0.85x, which is bright and large enough so you can focus manually with a degree of accuracy.
Perhaps the biggest selling point of the K-x over the K-m is the video-capture facility. Video footage can be recorded in 1280×720 resolution (16:9 ratio) and also a lower resolution 640×416 (3:2 ratio). It is a nice addition to the camera, although not one that I feel will hugely benefit enthusiast photographers.
With competition very fierce in this sector of the market, it is perhaps no surprise that the K-x comes in a choice of four colours, including a bright red that may attract a few more fashion-conscious photographers than the dowdy, conservative black we are now used to. In Japan, the K-x is actually available in 100 colour combinations.
However, the K-x is far more than a fashion accessory, as the improvements over the K-m are worthwhile. There are numerous in-camera options and settings, and certainly enough to keep someone learning photography interested. It should also be considered as a back-up DSLR for the K20D and K-7, especially as it features video capture. In all, it’s a great little DSLR with just a few areas in need of improvement.