Telephoto Lens
A lens that makes a subject appear larger on digital sensor than does a normal lens at the same camera-to-subject distance. A telephoto lens has a longer focal length and narrower field of view than a normal lens and have a shallower depth of field than wide angle lenses. But it can do isolation of subject and have a longer reach without going near to the subject. Life can be very difficult in sports and wildlife photography. Telephoto lens whose focal length is longer than the diagonal of the digital sensor frame; in 35mm photography, lenses longer than 50-5Bmm; also referred to as a "long" lens.
Through-The-Lens Focusing
Viewing a scene to be photographed through the same lens that admits light to the digital sensor. Through-the-lens viewing, as in a single-lens-reflex (SLR) camera, while focusing and composing a picture, eliminates parallax.
Through-The-Lens Metering
Meter built into the camera determines exposure for the scene by reading light that passes through the lens during picture-taking. Most SLR cameras have built-in meters which measure light after it has passed through the lens, a feature that enables exposure readings to be taken from the actual image about to be recorded on digital sensor, whatever the lens angle of view and regardless of whether a filter is used or not.
Tripod
A three-legged supporting stand used to hold the camera steady. Especially useful when using slow shutter speeds and/or telephoto lenses. Another is the monopod, single leg tripod.
Underexposure
A condition in which too little light reaches the digital sensor, producing a thin negative, a dark slide, or a muddy-looking print.
Unipod
Also refer as monopod.A one-legged support used to hold the camera steady. Also see "tripod".
Viewfinder.
Device or system indicating the field of view encompassed by the camera lens. The term is sometimes used as a description of the type of camera that does not use reflex or "straight-through" viewing systems and therefore has to have a separate viewfinder.
Vignetting
Underexposure of image corners produced deliberately by shading or unintentionally by inappropriate equipment, such as unsuitable lens hood or badly designed lens. A common fault of wide-angle lenses, owing to reflection cut-off, etc. of some of the very oblique rays. May be caused in some long-focus lenses by the length of the lens barrel.
Wide-Angle Lens
A lens that has a shorter focal length and a wider field of view (includes more subject area) than a normal lens.Also can explained as a lens whose focal length is shorter than the diagonal of the digital sensor frame; in 35mm photography, lenses shorter than 50mm; also referred to as a "short" lens.
Zoom Lens
A lens in which you adjust the focal length over a wide range of focal lengths. Subsituting lenses of many focal lengths. Zoom lenses whose focal length is continuously variable over a certain range without a change in focus; its focal length is changed by operating a separate zoom or a combination focusing/zoom ring; difficult type of lens to design and manufacture, very useful for the photographer on a budget or one who likes to travel light.
