Pentax K-x Review
Pentax K-x
Using the Pentax K-x
Record Mode
Flip the power switch and the K-x is ready to go almost instantly. If you've chosen to have the noisy dust reduction system run at startup it'll slow things down by about a second, though you can interrupt the process by pressing the shutter release button.
As usual, autofocus speeds depend on a number of factors, including the lens you're using and whether you're using live view. When shooting with the viewfinder, the K-x focuses quickly, though the lack of focus point indicators in the viewfinder is very annoying. Expect wide-angle focusing times between 0.1 and 0.3 seconds, with telephoto times ranging from 0.4 - 0.8 seconds (both with the 18 - 55 mm kit lens). Low light focusing is good, especially with the flash popped up (for AF-assist) -- expect focus times to stay under a second.
Things aren't nearly as nice when you're using live view. If you're using face or contrast detect AF, expect multi-second waits for the camera to lock focus. And forget about low light focusing -- it takes forever, and quite often the camera won't lock. For better results, use phase difference AF, which gives you the same speeds as when shooting with the viewfinder, plus about a second delay while the mirror does its thing. Do note that the AF-assist flash cannot be used when in live view.
As for shutter lag, there won't be any if you're shooting with the viewfinder, or using contrast detect AF in live view. If you're using phase difference AF in live view, there's about a second of lag due to the mirror flipping action.
Shot-to-shot delays are minimal, regardless of the image quality setting or whether you're using the flash.
You can delete a photo right after you take one by pressing the -- get ready -- delete photo button!
Now, here's a look at the available image size and quality choices on the K-x. Like on their point-and-shoot cameras, Pentax uses a star system to rate image quality, with 3 stars being the highest.
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As I mentioned earlier, the K-x supports not one, but two RAW formats. You can select from Pentax's PEF or Adobe's DNG format, both of which offer the same benefits of the RAW format that I discussed earlier. The camera allows you to take a RAW image by itself, or along with a JPEG of any size or quality.
One thing that hasn't changed with Pentax's cameras over the years is its menu system. If you went back five years ago and found an Optio camera, odds are that the menu would look a lot like the one on the K-x. That's not to say that the menu system is bad -- rather, it just looks dated, lacks any kind of help system, and could just be a little more user-friendly. The menu is broken down into four main tabs, covering shooting, playback, custom, and setup options. Here's what's available in the K-x's menu:
Shooting options
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Playback options
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Setup options
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Custom options
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As you can imagine, there's a lot to talk about before we can move on to our photo tests. Let's start with the Custom Image feature:
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| All the Custom Image sets | Tweaking the sharpness of the "bright" set |
A Custom Image "set" contains various exposure and color settings, and there are seven presets available: bright (default), natural, portrait, landscape, vibrant, muted, and monochrome. There aren't any custom sets, though -- you have to modify one of the presets. For each of these you can adjust the following:
- Saturation (-4 to +4)
- Hue (-4 to +4)
- Brightness [high/low key] (-4 to +4)
- Contrast (-4 to +4)
- Sharpness (-4 to +4) - a "fine" sharpness option is also available
- Filter effect (None, green, yellow, orange, red, magenta, blue, cyan, infrared) - for monochrome modes only
- Toning (-4 to +4) - lower numbers are "cold", higher numbers are "warm"
You can get a preview of the Custom Image settings by pressing the exposure compensation button, which takes a quick photo that is not saved to the memory card (by default).
The K-x has two dynamic range settings: highlight correction and shadow correction. Highlight correction is something that is turned on or off (it's off by default). It boosts the ISO to a minimum of 400 (it will use ISO 200 if ISO expansion is on), and then does its stuff. Shadow correction can be turned off (which is the default) or set to low, medium, or high.
Here's an example of the highlight correction feature in action:
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| Highlight correction on View Full Size Image |
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The highlight correction feature definitely improves highlight detail -- just look at the columns over on the right side of the photo. The bad news is that shadow detail really gets sacrificed in the process. Of course, you can also turn shadow correction on too, though I didn't get a chance to try that.
Speaking of which, here's how the shadow correction feature performed on the K-x:
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| Shadow correction off View Full Size Image |
Shadow correction low View Full Size Image |
Shadow correction med View Full Size Image |
Shadow correction high View Full Size Image |
If I could describe this feature in one word, it would be "subtle". The trees get a bit brighter, but don't expect massive amounts of brightness to suddenly appear.
Next up is Cross Processing, which is a technique that dates back to the film days. In those days, cross processing meant that you used the wrong chemicals when developing your film, to get photos that look a lot different than expected. Now it's a digital effect, and there are four modes to choose from (if you only have on or off, then you need to update your K-x's firmware). Pentax doesn't actually specify which each of the options does, so I'll just show you:
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| Cross Processing off | Standard CP | Cross processing 1 | Cross processing 2 | Cross processing 3 |
Pretty freaky if you ask me! The K-x has numerous digital filters that can be applied to images, either as you take them, or later in playback mode. You can even combine several of these filters into a new custom one, if you really want to go crazy.
Lens correction is another neat trick the K-x can pull off. Some cameras, notably from Panasonic, already apply distortion and chromatic aberration correction to photos you're taking, and those are both optional here. You can correct for lens distortion (both barrel and pincushion) as well as lateral chromatic aberration. You'll find an example of the barrel distortion correction in action a little further down the page, in the photo test section. Here's a crop showing the chromatic aberration correction at work:
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| Chromatic abberration correction off | Chromatic aberration correction on |
This as you may recognize is a crop from the "purple fringing tunnel of doom" at Stanford, that's included in every photo gallery on this site. This hallway is guaranteed to bring out the worst purple fringing in a camera, and it definitely does so here. And, look at that -- the CA correction feature did a pretty good job of reducing the amount of purple fringing AND highlight clipping in the photo. Do note that both distortion and lateral CA correction require some extra processing time after you take a photo. In addition, these features only work with modern DA, DA *, and DA L lenses.
The HDR Capture feature takes three exposures in rapid succession and combines them into a single image with high dynamic range. One image is underexposed, another is overexposed, and the third is of normal exposure. Since the images need to be precisely aligned, a tripod is essentially required for this feature. You can apply "standard" or "strong" HDR enhancement to a photo. Here's what this feature can do for you:
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| HDR off View Full Size Image |
HDR standard View Full Size Image |
HDR strong View Full Size Image |
There's no doubt that dynamic range is improved when using the HDR feature. That said, the resulting photos have that sort of washed out, surreal appearance that can be a trademark of HDR images. Do note that you can't take RAW images in HDR mode, and that the image stabilizer is turned off as well.
The multi-exposure feature lets you combine anywhere from two to nine exposures into a single image. You can choose to have the camera adjust the exposure (gain) automatically, if you'd like. The K-x doesn't have the time-lapse (interval shooting) mode of the more expensive K-7.
And what are those AF modes all about? AF-S locks the focus when you halfway-press the shutter release button. In continuous AF (AF-C) mode, the camera will keep focusing, even with the shutter release pressed -- great for moving subjects. The default setting, AF-A, automatically selects one of those two modes based on what's going on in the scene.
The last thing related to menus that I wanted to say is that the K-x has a rather large number of custom functions for a camera in this class. Many folks may not use them, but it's nice to know that they're available!
Alright, that's all for menus (phew) -- let's move onto photo quality now. With the exception of the night scene (which was taken with the F4.0-5.6, 50 - 200 mm lens), all of these test shots were taken with the 18 - 55 mm kit lens.
The Pentax K-x did a very nice job with our macro test subject. The colors look good, and the subject is quite sharp, especially for a digital SLR, whose images are often soft out of the box (I imagine that Pentax tweaked the sharpness to make the K-x more consumer-friendly). You can easily count the specs of dust on the figurine. The only issue I really have (and this is something that I encountered throughout my tests) is that it's hard to get accurate exposure if you rely on exposure compensation. The subjects were either too dark (see the studio ISO test later), or too bright (as in this case).
The minimum focus distance to your subject depends on what lens you're using. For the 18-55 kit lens, it's 25 cm. If you think you'll be doing a lot of macro photography, Pentax has four lenses for just that purpose, with focal lengths ranging from 35 mm to 100 mm.
The night shot is just "okay", and I think that's mostly due to the rather unimpressive 50 - 200 mm lens that Pentax sent along with the camera. The image is a bit on the soft side, with strong purple fringing. Put on a more impressive piece of glass, such as this guy, and I imagine you'd get a much sharper photo with very little purple fringing. There's also a considerable amount of highlight clipping, which is something that the K-x has some issues with. Still, the camera does capture a lot of detail, and there's no noise to be found here. And, as you'd expect, bringing in enough light is a piece of cake, thanks to the full suite of manual exposure controls on the K-x.
Alright, let's use that same scene to see how the K-x performs at its various ISO settings. I've opened up the full ISO range here (using the ISO expansion custom function), so now we're starting at ISO 100 and going all the way up to 12,800. I apologize for some minor inconsistencies in exposure between these photos -- turns out that the K-x and my Eye-Fi Pro card don't get along too well!
 ISO 100 (requires ISO expansion to be on) |
ISO 200 |
 ISO 400 |
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 ISO 1600 |
 ISO 3200 |
 ISO 6400 |
 ISO 12800 (requires ISO expansion to be on) |
The photos taken at ISO 100 through ISO 400 are all very clean. You start to see some increase in noise at ISO 800, but it's not nearly enough to concern me. The ISO 1600 shot came out darker than I wanted (though look for the DNG conversion below, which is okay), but you can still see that there's a bit more noise present, though it's still very usable for small and midsize prints. Detail loss becomes a lot more noticeable at ISO 3200, so now's a good time to start thinking about shooting RAW, or just sticking to small prints. I'd probably pass on ISO 6400, and definitely ISO 12,800.
Now let's see what the benefit of shooting RAW and doing some simple post-processing can do to improve your high ISO photos. There's a difference in exposure between the ISO 1600 JPEG and RAW conversion, since the JPEG at that shutter speed was corrupted.
| ISO 1600 |
JPEG, straight out of the camera |
 RAW -> JPEG conversion (ACR) |
 RAW -> JPEG conversion + NeatImage + Unsharp Mask |
| ISO 3200 |
JPEG, straight out of the camera |
 RAW -> JPEG conversion (ACR) |
 RAW -> JPEG conversion + NeatImage + Unsharp Mask |
| ISO 6400 |
JPEG, straight out of the camera |
 RAW -> JPEG conversion (ACR) |
RAW -> JPEG conversion + NeatImage + Unsharp Mask |
There's no doubt that you can get photos with more detail and less noise by shooting in the RAW format and using some noise reduction and sharpening filters -- up to a point. The improvement is quite noticeable at ISO 1600 and 3200, but not so much at ISO 6400, so I'd still probably avoid that sensitivity unless you're really desperate.
I was surprised to see some mild redeye on this digital SLR. Usually, since the flash pops up well away from the lens, redeye will not be a problem, but that's not the case here. And, for those who are wondering, I used the redeye reduction flash setting when I took this shot. Unfortunately, the K-x does not have a redeye removal tool in playback mode, so if you encounter this annoyance, you'll have to fix it on your computer.
Distortion correction off
Distortion correction on
The first distortion test chart you see above was taken with the 18 - 55 mm lens with the camera at its default settings. As you can see, there's some noticeable distortion, plus some vignetting as well (which wasn't a problem in my real world photos). When you turn on the distortion correction feature, things look a lot better -- look at how much straighter the lines are now. While blurring corners weren't an issue with this lens, things did seem sharper in the center of the frame than they did toward the edges.
Now it's time for our normal lighting ISO test, which is taken in our studio. Since the lighting never changes, this test can be compared to other cameras I've reviewed over the years. This image turned out a bit darker than I would've liked, but adjusting the exposure a bit higher make it too bright. And remember, While the crops below give you a quick idea as to the amount of noise at each ISO sensitivity, viewing the full size images is always a good idea. And with that, here we go:
 ISO 100 (only available with ISO expansion on) |
 ISO 200 |
 ISO 400 |
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 ISO 1600 |
 ISO 3200 |
 ISO 6400 |
 ISO 12800 (only available with ISO expansion turned on) |
Everything looks really clean though ISO 800, with minimal noise, found mainly in the shadows. There's a very slight increase in noise at ISO 1600, but it won't stop you from making large prints at this sensitivity. You start seeing some detail smudging at ISO 3200, which reduces your print sizes a bit, but it's still usable, especially with a little post-processing. ISO 6400 really isn't that bad, and could be used for small prints without any retouching. That said, a trip through Photoshop will give you even better results, as you'll see in a moment. I'd probably pass on the ISO 12,800 setting, which has too much detail loss to be usable.
Let's take the ISO 3200 and 6400 images and do some really easy post-processing on them. These were taken in the RAW (DNG) format, converted with Photoshop, and run through the NeatImage (noise reduction) and Unsharp Mask filters.
There's actually very little difference between the JPEG and retouched RAW images as ISO 3200, which tells me that Pentax's JPEG algorithms are pretty solid. Post-processing in Photoshop does make a more noticeable difference at ISO 6400, so I'd recommend spending the extra time to do that for your super-high sensitivity photos.
Overall, the Pentax K-x's photo quality was very good, though there's some room for improvement. The issues I have are mainly related to exposure. In many of my real world photos, the camera underexposed by 1/3 to 2/3 of a stop (though the reverse was true on one or two occasions). The K-x also clips highlights a bit more than I'd like. On a more positive note, colors are spot-on, and images are much sharper than your typical D-SLR (though photos are a bit soft toward the edges of the frame). I did notice some jaggies in some of my photos, which could be from the heavy sharpening the K-x is applying to its photos. The K-x does a nice job of keeping noise and noise reduction under control, until you reach the highest ISO settings. You will see some grainy noise in areas of low contrast (the sky being one example), but that won't be noticeable unless you're viewing the photos at 100% on your computer screen. Purple fringing is mostly a lens issue, and I found it to be moderate at times with the 18 - 55 mm kit lens.
Don't take my word for all this -- have a look at our extensive photo gallery and judge the K-x's image quality with your own eyes!
Movie Mode
The K-x features a high definition 720p movie mode. You can record videos at 1280 x 720 (24 fps) with monaural sound for up to 25 minutes or 4GB (whichever comes first). At the highest quality setting (***), you'll hit the file size limit in a little over eleven minutes. Thankfully, Pentax gives you three quality levels to choose from, so you can take longer movies if you wish. A lower resolution is also available -- 640 x 416, to be exact.
When you're recording movies, the image stabilizer is active, but it makes a lot of noise, and will likely be picked up by the microphone (watch the shake reduction sample video to see what I mean). You can zoom in and out to your heart's content, but the camera will not be continuously focusing. If you're in AF-S mode, you can hit the AF button to have the camera focus again, or you can just do it manually. The K-x can adjust the aperture automatically (to keep brightness consistent), or it can be fixed throughout the recording.
Movies are saved in AVI format, using the "dmb1" codec. File sizes are quite large, courtesy of a nearly 40 Mbps bit rate. Our sample movie, which is less than 10 seconds, is almost 49MB. The quality looks pretty good to my eyes, though the 24 fps frame rate seems more choppy than cinematic.
Here's a sample video for you, taken at the highest quality setting. I've got the huge 48MB original for you, or a recompressed QuickTime version whose colors don't look quite as nice.
View original movie (48.3 MB, 1280 x 720, 24 fps, AVI format)
View recompressed movie (6.0 MB, 1280 x 720, 24 fps, QuickTime/H.264 format)
Playback Mode
While they're not visible immediately, the K-x actually has a nice set of playback mode features. The basics are all here, including slide shows, DPOF print marking, image protection, thumbnail view, and playback zoom. This last option lets you blow up the image by as much as 16X, and you can then scroll around to check for proper focus, closed eyes, etc. A "quick zoom" option in the playback menu allows you to immediately jump to 2, 4, 8, or 16 times magnification.
All of the other playback bells and whistles can be reached by pressing down on the four-way controller. There you'll find tools for:
- Image rotation
- Digital filters (Toy camera, retro, high contrast, extract color, water color, pastel, miniature, base parameter adjustment [brightness, saturation, etc], monochrome [with filters], color filters, soft, star burst, fisheye, slim, HDR, custom)
- Image resizing
- Image cropping
- Slideshows
- Image comparison
- RAW processing
- Index print
- Image protect
- DPOF print marking
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| RAW editing | Side-by-side image comparison |
Two of those features are worth some further discussion. The RAW processing option lets you take a RAW image, adjust its properties, and save the result as a JPEG. You can adjust the image type, quality, and color space, the Custom Image setting, white balance, sensitivity, high ISO noise reduction, plus shadow, highlight, chromatic aberration, and distortion correction. Very handy! The side-by-side feature lets you look at two photos simultaneously, with the ability to maintain the zoom and position for both.
There's only one movie-related editing tool on the K-x, and that's to grab a still frame from your video. Why some camera manufacturers can't add a simple "trim movie" feature is beyond me.
The K-x can display plenty of information about your photos, including your choice of histograms. The camera moves from one photo to the next without delay.