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Pentax K20D: Reevaluating the Pixel
Digital Deal


At an ISO equivalency of 400, the K20D's picture remains clean and free of noise, even in the considerable shadow areas of this shot. The texture of the young lady's jacket is especially well-pronounced when the photo is viewed at full size.
Don Sutherland


Enormous 14MP+ image from Pentax's K20D provides a bright, snappy picture at ISO 200. The overall shot of New York's Memorial Day celebration has been reduced to fit our page-the image of the helicopter suggests the fine detail that can be captured in a full-size rendition of the picture below.
Don Sutherland


Don Sutherland



"How many pixels do ya need, anyway?" We're sure you've heard the question, and with a 14MP camera like the Pentax K20D, you're sure to hear it again.

Pixels. What a dynamic life they've led as camera marketing implements. At the dawn of the digicam, back when 640x480 pixels was a lot, adding more gave the gift of "more resolution." Little matter that the pixel count was only one factor in "how much resolution" you got from a camera. It was quantifiable, and easy to digest. If more horsepower makes a faster car, more pixels makes a higher-resolution camera. Right?

So in those pioneer days of digicams, 1996 and thereabouts, Canon with its original PowerShot 600 had the "most resolution"-its picture measured an eye-popping 832x624 pixels-a whole half-megapixel. How many pixels do ya need, anyway?

The Pentax K20D makes a picture measuring 4672x3104 pixels. That's how much we need. In fact, we need more.

HOW MANY MORE?

When we say "we," we mean "us," that is, the writer of this article (using the "editorial we"), not necessarily the whole world, as in "we shall overcome" or something. We mean us here, the one at the keyboard typing, the one who protested so oft and loudly so long ago, "Pixels aren't all there is to 'resolution!'" We've become pixel junkies, and we opine we can't have too many.

We don't expect everyone to agree, for there is a downside or two, theoretically at least, to piling on the pixels. For starters, the additional pixels represent additional data, additional stuff for the camera to process before writing the file. In other words, the camera must have a faster processor, or the user must get accustomed to slower burst-shooting, fewer pictures per burst, and/or a longer wait before the next shot.

SDHC memory cards such as those the K20D uses are now available in 32-gigabyte capacities, and that's good. At 41.5 megabytes per picture (in high-quality JPEG format), storage space fills quickly. They probably won't send anyone to the poorhouse, but the extra-large files also consume more space in disk drives and optical discs for backup. What exactly do you get for all the big bucks?

Noise. All other things equal, a camera with more pixels will make a noisier picture than a camera with fewer, because the "pixels" on the imager must be correspondingly smaller to fit the space. Among the things that must be "equal," of course, is the size of the imager. Going to a 12MP imager created the rationale, in Nikon's mind at least, to go to a full-frame sensor (about 36x24mm). This permitted larger pixels on the chip, but it also sparked some pyrotechnics among critics who perceived an abandonment of Nikon's traditional digital-lenses-for-digital-imagers pitch. As we write, we know of no full-frame lenses that boast the special features attributed to digital-specific lenses.

The Pentax K20D uses an APS-C-size imaging chip (and Pentax's extensive line of digital-specific lenses), same size as the camera's predecessor, the K10D, used with 10MP. Indeed, it's the same size as the 6MP imager used by the original Pentax *ist DSLRs. We lavished praise on those DSLRs for their low-noise results at the higher ISO equivalencies -they made very decent pictures at 1600 speed. But no one would expect an imager with more than twice the pixels in the same space to produce the same results. What results should you expect, and how many pixels do ya need, anyway?

THE WHYFORES OF MULTI-MEGAPIXELS

Digital tech has wrought resounding wonders in reshaping the practice of photography, and it's also wrought some subtle ones, too. For example, with a digital camera you can change the ISO equivalency from one frame to the next-a principle that was attempted a couple of times with 35mm film, but as a successful practice is a distinctively digital trait. The Pentax K20D can be set anywhere from ISO 100 to ISO 3200 equivalency for every picture it takes.

Another resounding wonder of digital tech is the oscillating imager, the one that jitters around inside the camera body in opposition to shake and tremor-the Shake Reduction feature, in Pentaxian. You couldn't accomplish the same result with a long strip of film, but in digital it's now considered a standard.

Each of these two resounding features brings something seriously useful to the practice of photography, but their additional, more subtle effect involves lenses. If you can raise the ISO equivalency to order, and if you have a Shake Reduction feature, you have a camera that presumably can take handheld pictures in lower levels of light. You could also take handheld pictures in lower light if you used much faster lenses, but faster lenses are expensive. Shake Reduction and adjustable ISO equivalents aren't.

So fairly quietly, the whole industry has seen a shifting of values in lens features. Not an absolute shift, not a universal one, but enough of a shift to be called an option-some customers may find it wiser to buy a camera with Shake Reduction and variable ISO for low-light shots with an f/4 lens. It'll work, at least some of the time. However, if the customer is wont to photograph fast-traveling subjects in low light, an f/2.8 or faster lens will still prove better.

A similar set of options (or trade-offs, if you prefer), accompanies multi-megapixel imagers. To a degree, you can control distractions like noise by downsizing the picture. Why shoot a photo at 4672x3104 pixels? One reason is because it might make a superior email attachment at 640x480 pixels.

THE BIG SQUOOSH

There are a lot of misconceptions about the role of size in photography. You'll hear a lot of people say that the purpose of medium- and large-format photography back in the days of film was to gain the extra quality-that is, "resolution"-those large films could capture. Well, maybe. They captured extra quality if the lenses on the cameras were extra good. Generally they weren't. Quite frequently, medium- and large-format lenses were allowed to be "less sharp" than 35mm lenses, because they could be. The larger film made up for the difference, when printed at the reduced sizes for photo frames or magazine pages. The lenses produced for 35mm cameras were much sharper, because they had to be-rather than reductions, almost all their prints would be enlargements, needing all the help they could get.

More than a picture with "more resolution," medium- and large-format films brought the "workflow" advantages of easier handling-easier to look through in filing cabinets, easier to retouch by hand. Such virtues no longer apply in the digital age.

But the principle of downsizing from a larger digital picture comes with many of the same attractions in digital that it did in film. Is the subject a little blurred, despite Shake Reduction (which can't correct for subject motion)? It's harder to see in a smaller picture. Ditto noise and other kinds of artifacts-a lot of them get interpolated out.

Camera manufacturers used to draw scorn for promoting a "digital zoom" feature which, as the intelligentsia pointed out, was nothing more than a cropped section of an already limited number of pixels. But when you start with over 14 million, a cropped section need not be so limited. It wasn't long ago that 6-megapixel cameras were state of the art, making frames of about 3000x2000. That's still a good size for the majority of common applications-so the "digital zoom" concept gains a renewed respectability.

We wouldn't say that the reducibility of a 14MP photograph is its most significant selling point. But it is an evolutionary factor in photography that's becoming apparent for the first time. It's changing a few ways we can think about how to present our cameras, how to use them.

THE K20D AS IT IS

While the accents and the emphases of photography are evolving through the auspices of advanced cameras like the K20D, they bring something more direct to the picture-taking process. That is, the K20D is one of those digital cameras that can work almost anywhere, being heavily armored and splashproofed. It has all the features we loved about the K10D, including a RAW button that writes files in a RAW format (Pentax's own, or Adobe's DNG-user's choice) for as long as it's pressed; once released, the camera writes JPEGs.

Also on deck is a selector lever for the AE reading pattern-matrix, center-weighted, spot-a control that's relegated to menu settings on a number of cameras. It's better to have as a discrete control on the top deck, per this Pentax, because it's the type of thing a photographer might want to change swiftly from picture to picture.

The K20D is the first Pentax DSLR with a live-view feature, another enormously useful addition recently added to the roster of standards in DSLRs. The screen itself is appreciably larger than that of the K10D.

We were certainly pleased with the picture characteristics of the K20D at ISO equivalencies up to 400. Even 800 was very good, with only the beginnings of some chrominance noise beginning to emerge-but only beginning-in the shadow areas. Chrominance noise was more pronounced at 1600 equivalency when the picture was full size-but at 50% on-screen, the chrominance noise practically disappeared, leaving us with some handsome pictures. At the slower speeds of 200 and 100, or course, the pictures are gorgeous.

Pentax scores another hit with the K20D, a high-value camera with a lot of capability, at a modest price. It's a market leader at pixel count for the moment. But even with over 14 million of 'em, it doesn't answer the question of how many do ya need, anyway? We'll come back to that and a few other newfangled themes a few issues hence.


   







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