Tuesday, January 28, 2014
Be A Digital Ansel Adams
Essential gear to help you adopt an Ansel Adams-type workflow with today’s latest photography tools and technology
Megapixels are important, of course, because they largely determine the level of detail an image can contain and how big a print you can make (all assuming the image is sharply focused and not blurred by camera or subject movement). But there are other important digital camera considerations. One is dynamic range, which means how great a scenic brightness range can be recorded without blowing out highlights or losing shadows to noise. Most newer DSLRs produce very good dynamic range; check DxOMark.com for their test results on current DSLRs. If you look at Adams' work, you'll notice that he shot in a variety of conditions, from bright midday sun to twilight. He relied on different film emulsions and his mastery over the darkroom process of film development and printmaking. Today, we can make use of a DSLR's ISO range to give us the ability to shoot in that broad range. The best cameras for high-ISO work are the newer full-frame DSLRs. While Adams had to deal with reciprocity failure and expertise with chemistry, we can shoot in low light much easier with one of these newer cameras.
The photodiodes (pixels) in conventional image sensors can't detect color; they record only how much light is striking them, not its wavelength(s). To obtain color information, most sensors use a Bayer filter array, which positions a red, green or blue filter over each pixel, so that each pixel receives mainly red, green or blu light. The missing colors are obtained by interpolation using data from neighboring pixels and complex proprietary algorithms.
One problem with this system is that it can result in moiré and other artifacts when a finely patterned subject's image at the focal plane conflicts with the pattern of the sensor's pixel grid. This is especially possible with Bayer sensors because they record only one primary color at each pixel site. To minimize moiré and artifacts, manufacturers position an anti-aliasing (AA) filter (also known as an optical low-pass filter, or OLPF) over the sensor. This blurs the image's high frequencies (fine detail) at the pixel level, eliminating or greatly reducing moiré, but also slightly reducing image sharpness.
Medium-format digital cameras and backs don't use AA filters because users of these devices are concerned with maximum sharpness and prefer to deal with any moiré and artifacts that occur on a per-image basis during postprocessing.
Some manufacturers now offer DSLRs without an OLPF. The pixel density is so great on these 16- and 24-megapixel APS-C and 36-megapixel full-frame models that moiré is less likely to be visible. These include Nikon's 24-megapixel APS-C D5300 and D7100 and 36-megapixel full-frame D800E (with an AA filter, but its effect has been negated), Pentax's 16-megapixel APS-C K-5 IIs and 24-megapixel K-3 (incorporates an AA filter simulator you can activate, when desired) and all Sigma DSLRs (their Foveon X3 sensors record all three primary colors at each pixel site and don't suffer from color moiré). Mirrorless interchangeable-lens cameras without an AA filter include the 16-megapixel Fujifilm APS-C X-Pro1, X-E1, X-E2 and X-M1 (their X-Trans sensors use a non-Bayer color-filter pattern that's less likely to produce moiré) and Sony's 36-megapixel full-frame a7R. If you're looking for Adams-type sharpness in a small camera, consider one of these AA-less models.
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