A full-frame digital SLR is a digital single-lens reflex camera (DSLR) fitted with an image sensor that is the same size as a 35 mm (36x24 mm) film frame. This is in contrast to cameras with smaller sensors, typically of a size equivalent to APS-C size film, much smaller than a full 35 mm frame. As of 2007, the majority of digital cameras, both compact and SLR models, use a smaller-than-35 mm frame, as it is easier and cheaper to manufacture imaging sensors at a smaller size. Historically, the earliest digital SLR models, such as the Kodak DCS 100, also used a smaller sensor.
Use of 35 mm film camera lenses
If the lens mounts are compatible, many lenses, including manual-focus models, designed for 35 mm cameras can be mounted on the latest DSLR cameras. When a lens designed for a full-frame camera, whether film or digital, is mounted on a DSLR with a smaller sensor size, only the center of the lens’s image circle is captured. The edges are cropped off, which is equivalent to zooming in on the center section of the imaging area. The ratio of the size of the full-frame 35 mm format to the size of the smaller format is known as the “crop factor” or “focal-length multiplier″, and is typically in the range 1.3–2.0 for non-full-frame digital SLRs
Advantages and dis-advantages of a full frame DSLR
Full-frame DSLR cameras offer a number of advantages over their smaller-sensor counterparts. One advantage is that wide-angle lenses designed for full-frame 35 mm retain that same wide angle of view. On smaller-sensor DSLRs, wide-angle lenses have smaller angles of view equivalent to those of longer-focal-length lenses on 35 mm film cameras. For example, a 24 mm lens on a camera with a crop factor of 1.5 has a 62° diagonal angle of view, the same as that of a 36 mm lens on a 35 mm film camera. On a full-frame digital camera, the 24 mm lens has the same 84° angle of view as it would on a 35 mm film camera.
There are optical quality implications as well—not only because the image from the lens is effectively cropped—but because many lens designs are now optimized for sensors smaller than 36 mm × 24 mm. The rear element of any SLR lens must have clearance for the camera's reflex mirror to move up when the shutter is released; with a wide-angle lens, this requires a retrofocus design, which is generally of inferior optical quality. Because a cropped-format sensor can have a smaller mirror, less clearance is needed, and some lenses, such as the EF-S lenses for the Canon APS-C sized bodies, are designed with a shorter back-focus distance; however, they cannot be used on bodies with larger sensors.
In addition to wide-angle photography, another major advantage of full-frame cameras is pixel size. For a given number of pixels, the larger sensor allows for larger pixels or photosites that provide wider dynamic range and lower noise at high ISO levels. As a consequence, full-frame DSLRs may produce better quality images in certain high contrast or low light situations.
The full-frame sensor can also be useful with wide-angle perspective control or tilt/shift lenses; in particular, the wider angle of view is often more suitable for architectural photography.
While full-frame DSLRs offer advantages for wide-angle photography, smaller-sensor DSLRs offer some advantages for telephoto photography because the smaller angle of view of small-sensor DSLRs enhances the telephoto effect of the lenses. For example, a 200 mm lens on a camera with a crop factor of 1.5 has the same angle of view as a 300 mm lens on a full-frame camera. The extra "reach", for a given number of pixels, can be helpful in specific areas of photography such as wildlife or sports.
Production costs for a full-frame sensor can exceed twenty times the costs for an APS-C sensor. Some full-frame DSLRs intended mainly for professional use include more features than typical consumer-grade DSLRs, so some of their larger dimensions and increased mass result from more rugged construction and additional features as opposed to this being an inherent consequence of the full-frame sensor.
Past & present full frame DSLR cameras
Contributed by: Mohinder Pal Singh
Date: July 14, 2010