on April 19, 2011
I've shot with the K-5 for a month now, and I'd like to share my viewpoints on it.
First, the noise level in the high-ISO images really is as excellent as the technical reviews say it is. This means that you can use a higher ISO number and get results equivalent to other cameras at lower ISO numbers. You can take your shot with either a faster shutter time (better motion freezing) or smaller aperture (better sharpness, etc) or just enjoy the reduced noise. This puts the camera at an advantage over all other APS-C cameras and a few of the full frame cameras.
Next, the movie mode is a mixed bag. It has the 1920x1080 at 25fps setting, as well as 1280x720 at 30fps settings, and lower settings too. The 25fps setting is often quoted as a major problem, with videographers wanting to shoot 23.976fps as a "cinema" mode, but it takes only a bit of video conversion to change the frame rate to 23.976 and resample the 32k s/s stereo signal to match. So, if you're desperate you can manage, but even then it is clear that this is not a camera for someone who wants video as a major use. The biggest problem is the inability to autofocus while shooting. The worst-case test of this is shooting a 2-year old running around in a house. Being indoors with available light, the aperture is open and depth of field is short; as soon as the child runs towards you the focus is way out. The camera is simply not usable in this kind of situation. On the other hand, with available light and a subject which is not in wild motion, the results are acceptable, but even then, a much less expensive camcorder often gives superior results. The only place where the K-5 shines in video is if you are outdoors, and you have a 500mm telephoto mounted, and you want video of distant wildlife - then, you have a system giving nice results. However, again, if you want a camera with great video capability and very good but not quite great still capability, go for the Panasonic-DMC-GH2.
Next, color gradient linearity. A partly subjective criteria, not an easy item to quantify, but not too hard for a professional photographer to see. This is the quality of a color image which makes it as lifelike and genuine-looking in the shadows and highlights as in the midranges. A face is a good choice, especially a baby's face - a fair skinned baby should have subtle colorations in the midranges perceivable because their skin is so thin it is nearly transparent. The shadows should look like skin in shadow, not various types of dirty brown, and the highlights should look like brightly illuminated skin not just brightly-colored areas. Being able to set the K-5 with 14-bit linearity may be the key to its terrific color gradient linearity. The K-5 has a wonderfully realistic treatment of living things, and subtle colors which extend from bright to dark look authentic in a way which the eye can see but which are hard to describe - to put a phrase on it, the beauty of the image is deep. The genuineness of the color gradients give a realistic sense of depth which stay in the image even after you have blown it up and put it on your wall. Again, this is hard to quantify, but you won't see this much in the Panasonic GH-2. Or even the Canon Rebel 550D. Pentax has gotten this just so right. I've seen Nikon D7000 shots with similar qualities, but I'd have to still give the K-5 the advantage here. To me, this is one of the deciding features of the K-5, and it has nothing to do with all the technical tests at which it has excelled.
Let me say a few words about the image stabilization, which unlike most cameras is in the camera body. You can put any lens on the camera, including old classics, and get modern image stabilization. If you try this with Canon, you will end up stuck on your tripod. Why don't other manufacturers do this? And yes, it works extremely well. Even for long lenses.
Now, auto-focus. I have to say, when shooting a still subject the K-5 is near perfection. It is fast and positive in bright light, slower but certain in fairly dim light. If it fails to find a focus in autofocus mode, it will not acknowledge the shutter press. The focus-assist LED is excellent and works well for darkened rooms, but only for distances less than about 5 feet, above that it gets a little less reliable. I sometimes take flash shots in absolute darkness of subjects over 5 feet away, and I've gotten good results using a small hand held flashlight to get a temporary focus, then hold it and turn off the flashlight, and take the shot. This gives you the ability to get dramatic shots like an animal in water at night, splashing, with every drop suspended in air. On the other hand - the situation with a baby running around in circles in front of you, the test I gave for the video mode focus problem, remains a worst case. Moving to continuous focus mode, you get excellent sharp shots, but the timing may be awkward - for instance, with the child running in circles, I got many shots at the point the child turned to run away, when I wanted to get the shot a half second earlier. But enough shots were sharp and well-timed to make it a good experience. Doing the same test with the Canon 550D gave an advantage to the Canon's AI-Servo mode focus, which seemed to follow the child much better - but in many cases, the shot, when taken, was not as well focused as the K-5. So summing up the results for the Canon 550D, I got better autofocus speed, but inferior accuracy. Both cameras can give good results, but the photographer needs to know each camera's weaknesses.
I ordered my K-5 from Amazon Warehouse Deals a month ago, and quickly noticed that the front setting wheel was defective. You could turn it and it would sometimes ignore you, other times skip values, so that in manual mode, where you need both the forward and rear wheels, it was difficult to use. As days passed the problem got worse, so I sent the camera back to Amazon (thanks to their excellent return policy). Being an engineer myself, I recognized it as an optoelectronic component failure, not a design issue, so I felt confident that a replacement would not have the problem again, and this did not bias me against the K-5. While waiting for my refund, I spent the time carefully looking at my photos and thinking whether any other camera would better fit my needs. The cameras which came the closest were the Panasonic Lumix GH-2 and the Nikon D7000. But I couldn't avoid coming to the same conclusion. I reordered the K-5 because of its low noise level, wonderful color linearity, unique in-camera image stabilization, rugged weather sealing, and compatibility with the excellent Pentax Limited lenses. To me it was well worth the extra money, because no other camera has these same features.