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Tuesday, February 8, 2011

Would Ansel Adams Use A DSLR?

If Ansel Adams were shooting digital, would a DSLR be his tool of choice? We look at the requirements of a serious landscape shooter and see if today’s best cameras are up to the challenge.

Labels: Gear

This Article Features Photo Zoom

21 Megapixels

A small step in resolution below the 24-megapixel models, we find a pair of full-frame, 21-megapixel DSLRs from Canon: an all-out pro flagship camera and a much-lower-priced model with a similar sensor and HD video capability, too.

Canon EOS 5D Mark II. The EOS 5D Mark II created a sensation upon introduction for its 1080p full HD video capability, but it’s a first-rate still camera, too. Featuring essentially the same 21.1-megapixel Canon CMOS sensor as the flagship EOS-1D Mark III, but with a newer DIGIC 4 processor in place of the Mark III’s dual DIGIC IIIs, it delivers what Canon called the best image quality ever for a Canon DSLR. And that—along with its $2,499 price tag—makes it a great choice for a landscape camera in the 21-megapixel category. The EOS 5D Mark II also is smaller and lighter than the flagship model (albeit not quite as rugged), has a better LCD monitor (921,000 dots vs. 230,000) and, of course, can shoot full HD video, while the EOS-1Ds Mark III has no video capability. Estimated Street Price: $2,499.

Also Consider: If you shoot landscapes in really harsh conditions, you might prefer Canon’s top-of-the-line DSLR, the EOS-1Ds Mark III. It provides essentially the same sensor and image quality as the 5D Mark II, but features a more rugged, weatherproof construction. It’s also quicker, has a better AF system and has slots for both CompactFlash and SD memory cards. Estimated Street Price: $6,999.

More Than Just Pixel Count
Basically, pixel count determines how big a print you can make from a digital file: the more pixels, the larger the print before the eye can see the actual pixels. And the more pixels, the finer the detail that can be rendered. But other things besides pixel count determine image quality, and even resolution. Other factors affecting image sharpness include the anti-aliasing filter over the sensor, the ISO setting, the exposure, the lens and aperture used for a shot, the shutter speed and whether the camera is handheld or on a sturdy tripod with a good head.

And there’s more to image quality than just resolution/resolving power/sharpness. Dynamic range—how much detail, from the darkest area of a scene through the brightest, a sensor can reproduce (and the entire camera/lens/printer system can reproduce in a print)—is important to landscape photographers. Bit depth—the number of tones or shades of color a sensor can reproduce—is also important. Some DSLRs record RAW images at 12 bits (4,096 shades from black to white), some at 14 bits (16,384 shades). Most medium-format DSLRs record RAW images at 16 bits (65,536 shades). JPEG images are always 8 bits (256 shades from black to white). The greater the number of tones/shades of gray, the smoother the resulting images. But keep in mind that you won’t always be able to see the difference between 12-bit and 14-bit images, or 14-bit and 16-bit, in an inkjet print, and higher bit depths mean larger image file sizes. A higher bit depth can be handy if you have
to make a large Levels adjustment when editing an image: If you have to move the left and right Levels sliders 15% to yield true black-and-white tones (an extreme example, granted), with a 12-bit image, you’ll still have 11,469 tones in the image (16,384-4,915); with an 8-bit JPEG, you’d have just 180 tones (256-76).

Resolution, dynamic range and bit depth are best at lower ISO settings. Higher ISO settings (all those above the camera’s “native” ISO, which is usually the lowest one in the camera’s “normal” ISO range) are produced by increasing the gain (amplifying the image data), which increases image noise (digital “grain”), and decreases dynamic range, bit depth and detail. Generally, the “best” ISO for overall image quality is the lowest one in the camera’s “normal” ISO range, but Ansel Adams would have tested that with his camera(s) to be sure, and you should, too, for best results.

DxO Labs, best known for its DxO Optics Pro lens-correction and RAW-processing software, also makes gear used by members of the photo industry to test their own products. DxO has tested RAW image quality of popular digital camera sensors and posts the results on its DxOMark website (www.dxomark.com). Sensors are rated in three main categories (color bit depth, dynamic range and low-light ISO) and given an overall score computed from these results. While your results may vary, and there are other important considerations (including resolution, lens quality, ergonomics, AF performance and camera speed if you do wildlife action like birds in flight, etc.), the DxOMark results are a valuable asset when you’re trying to choose a digital camera. (To get the most value from the DxOMark data, look at the graphs provided, as well as the numerical scores, as these provide additional information, including performance at different ISO settings.

Note that DxOMark scores are for RAW sensor performance and aren’t necessarily representative of a camera’s JPEG images (Adams, of course, would have shot only RAW images).


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