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The term full frame is used by users of digital single-lens reflex cameras (DSLRs) as a shorthand for an image sensor format which is the same size as 35mm format (36 mm × 24 mm) film. Historically, 35mm was considered a small film format compared with medium format, large format and even larger. This is in contrast to cameras with smaller sensors (for instance, those with a size equivalent to APS-C-size film), much smaller than a full 35mm frame. Currently, 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 Nikon NASA F4 or Kodak DCS 100, also used a smaller sensor. Kodak states that 35mm film has the equivalent of 6,000 pixel horizontal resolution according to a Senior Vice President of IMAX.
Contents
- Use of 35mm film camera lenses
- 35mm lenses
- DSLRs
- Rangefinders
- Other technologies
- Prototype full frame digital SLRs
- References
Use of 35mm film-camera lenses
If the lens mounts are compatible, many lenses, including manual-focus models, designed for 35mm cameras can be mounted on 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' 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 35mm 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.
35mm lenses
When used with lenses designed for full frame film or digital cameras full-frame DSLRs offer a number of advantages compared to their smaller-sensor counterparts. One advantage is that wide-angle lenses designed for full-frame 35mm 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 35mm 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 35mm film camera. On a full-frame digital camera, the 24 mm lens has the same 84° angle of view as it would on a 35mm film camera.
If the same lens is used on both full-frame and cropped formats, and the subject distance is adjusted to have the same field of view (i.e., the same framing of the subject) in each format, depth of field (DoF) is in inverse proportion to the format sizes, so for the same f-number, the full-frame format will have less DoF. Equivalently, for the same DoF, the full-frame format will require a larger f-number (that is, a smaller aperture diameter). This relationship is approximate and holds for moderate subject distances, breaking down as the distance with the smaller format approaches the hyperfocal distance, and as the magnification with the larger format approaches the macro range.
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.
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.
Lower size sensors also allow for the use of a wider range of lenses, since some types of optical impurities (specifically vignetting) are most visible around the edge of the lens. By only using the center of the lens, these impurities are not noticed. In practice, this allows for the use of lower cost glass without corresponding loss of quality.
Finally, full frame sensors allow for sensor designs that result in lower noise levels at high ISO and a greater dynamic range in captured images. Pixel density is lower on full frame sensors. This means the pixels can be either spaced further apart from each other, or each photodiode can be manufactured at a slightly larger size. Larger pixel sizes can capture more light which has the advantage of allowing more light to be captured before over saturation of the photodiode. Additionally, less noise is generated by adjacent pixels and their emf fields with larger photodiodes or greater spacing between photodiodes. 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.
Production costs for a full-frame sensor can exceed twenty times the costs for an APS-C sensor. Only 20 full-frame sensors will fit on an 8-inch (200 mm) silicon wafer, and yield is comparatively low because the sensor's large area makes it very vulnerable to contaminants—20 evenly distributed defects could theoretically ruin an entire wafer. Additionally, when full-frame sensors were first produced, they required three separate exposures during the photolithography stage, tripling the number of masks and exposure processes. Modern photolithography equipment now allows single-pass exposures for full-frame sensors, but other size-related production constraints remain much the same.
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.
DSLRs
The Nikon E2/E2s (1994), E2N/E2NS (1996) and E3/E3S (1998) digital SLRs as well as the similar Fujifilm Fujix DS-505/DS-515, DS-505A/DS-515A and DS-560/DS-565 models used a reduction optical system (ROS) to compress a full-frame 35mm field onto a smaller 2/3-inch (11 mm diagonal) CCD imager. They were therefore not digital SLRs with full-frame sensors, however had an angle of view equivalent to full-frame digital SLRs for a given lens; they had no crop factor with respect to angle of view.
Nikon has designated its full frame cameras as FX format and its smaller sensor cameras as the DX format.