Easy-to-understand,  non-technical explanations of terms commonly associated with digital single lens reflex cameras and accessories.

DSLR Glossary

APS (Advanced Photo System)

Often called APS-C (for classic). Format first developed for film (for example, with the Kodak Advantix system) and is now used by most manufacturers as their reference for sensor size. There are slight variations in actual size between some manufacturers.

Aspect ratio

While most point-and-shoot cameras offer an aspect ratio of 4:3 (the equivalent of a regular television or computer screen), most DSLR sensors have an aspect ratio of 3:2 (the equivalent of a standard 4x6 inches picture). The two numbers of the aspect ratio simply represent the relative lengths of the longest and shortest sides of the image rectangle.

Body

The camera minus the lens. The body contains the sensor, batteries, processor, controls and user interface.

Dust

One problem of DSLRs is that when you remove lenses, the sensor area becomes exposed to ambient air, and can collect dust. Moreover, moving parts inside the camera can create fine particles, too, and these can deposit on the sensor. (This wasn’t a real problem with film cameras, because the “sensor” -film- changed with every frame). Most manufacturers now offer dust removal systems with their cameras. Good technique (holding the camera face down when changing a lens, avoiding changing lenses in very dusty environments, for instance) will reduce the risks of gathering dust.

Dynamic range

The gradations and range of light intensities (between total black and total white) that a sensor can detect and record. For instance, past a certain brightness, any sensor will saturate and will not be able to display colors accurately, delivering an over-exposed (pure white) output. This often happens when using a flash to photograph a close subject, or under bright sunlight. Larger sensors, such as those found in DSLRs, typically have a much broader dynamic range.

Focal length multiplier

Most sensors used in DSLRs have a smaller area than the surface of 35mm film. Yet, for historical and convenience reasons, focal lengths are still expressed in the 35mm format. This means that each camera’s effective focal length will be different than the one listed on a lens. To calculate the effective focal length of a lens and camera combination, the user must use the focal length multiplier of the camera. Canon’s entry-level cameras’ multiplier is usually 1,6, though their higher-end models do not have a multiplier. Nikon, Sony and Pentax usually have a multiplier of 1,5, while four-thirds systems (such as Olympus and Panasonic) have a multiplier of 2. As an example, a 50 mm lens on a Nikon camera would have an effective focal length of 75 mm, while a 12-48 mm zoom lens on a four-thirds system would have an effective reach of 24-84 mm.

Four-thirds

A lens system and sensor size mainly supported by Olympus and Panasonic. The four-thirds system aims at standardizing the lens mounts, sensor size and communication protocol between camera and lens. The idea is to make the lenses and camera bodies interchangeable between brands. The four-thirds system is a digital-only system, meaning that no film camera is standardized for it. The sensors used in the four-thirds system are slightly smaller than most other digital sensors, allowing lenses to also be physically slightly smaller. The smaller sensors also mean that noise levels are often a bit higher than what is obtained with larger sensors.

Full frame

A sensor format that corresponds to the area of traditional 35 mm film, mainly used by Canon in some high-end models. Full-frame cameras have no focal length multiplier (or, said differently, they have a multiplier of one). Lenses designed specifically for digital cannot be used on full-frame cameras, except if the user is willing to accept strong vigneting in all circumstances.

Kit lens

A lens (or lenses) offered as a starter kit with a DSLR camera. Buyers can purchase only the camera body, but kit lenses are an inexpensive starting point for a new DSLR owner. These lenses are rarely excellent, even though they will satisfy many users

Parfocal

An interchangeable lens that remains in focus when the focal length is changed

Sharpness

Sometimes unprocessed DSLR images look less sharp (softer) than what a good point-and-shoot will deliver. This is not a flaw of DSLRs, but rather a choice made when programming the image processor of the camera. Manufacturers often assume that DSLR users will want to process their images with a computer and software (such as PhotoShop), and thus leave the internal processing to a minimal level. Most of the times, image parameters can be fine-tuned by the user.

Third-party lenses

Some lens manufacturers design the optical elements of a lens, then adapt the design to fit on the various mounts of the most common brands. The three best known third-party manufacturers are Sigma, Tamron and Tokina, but there are others. Some brands license their communication protocols to third-party manufacturers, but not all, which means that sometimes reverse engineering is necessary for third-party manufacturers to make lenses communicating with a camera. Third-party lenses can be just as good as original brand lenses, and often equal-quality lenses will be less expensive when purchased from third-party manufacturers.