Tuesday, July 6, 2010
DSLR Performance In A Point-And-Shoot Size?
The new class of cameras—mirrorless, interchangeable-lens models—gives serious nature photographers some interesting options
Mirrorless, interchangeable-lens cameras have DSLR-sized image sensors. Those from Olympus and Panasonic have 17.3x13.0mm Four Thirds System sensors, while those from Samsung and Sony have 23.4x15.6mm APS-C sensors, the size used in many popular entry- and mid-level DSLRs. By comparison, typical higher-end compact digital cameras have sensors one-fifth to one-eighth that size.
The significance of these numbers is this: Smaller sensors can make for smaller cameras (although Sony’s APS-C-format NEX-3 and NEX-5 are currently the smallest mirrorless models). But bigger sensors have more room for more pixels of a given size, or larger pixels for a given pixel count. And all things considered, more pixels, and larger pixels, are better. More pixels mean the ability to make bigger prints before the eye can make out the pixels, as well as the ability to picture finer detail. Larger pixels mean more light-gathering efficiency, which translates to better low-light and high-ISO performance. The mirrorless, interchangeable-lens cameras produce far better image quality than the compact digital cameras, especially at higher ISO settings: true DSLR image quality.
Another important facet of sensor size is its effect on a lens’ field of view. Smaller sensors crop into the image produced by any given lens, creating a “telephoto” effect. Camera manufacturers list a focal-length factor for their digital cameras based on the sensor’s field of view vs. a “full-frame” 35mm image frame’s field of view. A full-frame DSLR frames just like a 35mm SLR; the focal-length factor for full-frame sensors is 1.0x. An APS-C sensor crops in on the image formed by the lens such that it covers the field of view of a lens 1.5x longer on a 35mm camera; hence, its 1.5x factor (Canon’s slightly smaller APS-C sensors have a 1.6x factor, Sigma’s, a 1.7x factor). The even smaller Four Thirds sensor has a 2x factor: A 100mm lens on a Four Thirds (or Micro Four Thirds) System camera frames like a 200mm lens on a 35mm camera.
This is great for sports and wildlife photographers, who seldom can get close enough to subjects for dramatic frame-filling shots: All your lenses are, in effect, 1.5x, 1.6x, 1.7x or 2x “longer.” It’s not so good for wide-angle landscape photographers, whose wide-angle lenses also become “longer” and less wide-angle: A 24mm lens on an APS-C camera frames more like a 40mm lens on a 35mm camera; a 24mm lens on a Four Thirds (or Micro Four Thirds) System camera frames like a 48mm lens on a 35mm camera.
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