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This is the widest aperture that can be selected on the camera and is an indication of the speed of the lens. On zoom lenses two figures are often given. One is for the lens at the wide-angle setting and the other is for the telephoto setting.
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An optical effect which can soften photographs and make them less sharp. As long as light travels in straight lines, this phenomenon will not occur, but as soon as it starts to bend - disperse or "diffract" - when it has to travel through a hole so small that it has to squeeze through, it will begin to interfere with the quality of the final result. Although a negligible effect in most situations, it actually increases with smaller apertures. There is a break-even point at which the disadvantage of the diffraction of the light captured is still compensated by the advantage of extra sharpness due to greater depth of field. But beyond that point the softening effect of the diffracted light is only partly compensated by the sharpness due to the greater depth of field. Finding the break-even point can help prevent any negative effects of diffraction. And as a bonus it will limit the length of the exposure or the ISO needed to take a photo with a very small aperture. The difficulty is that the effect isn't the same for different cameras and lenses. The aperture isn't the only critical factor - the size of the film or sensor recording the photo counts as well, and so does the quality and the focal length of the lens. For those who don't want to get into complicated mathematical calculations in order to find the ideal aperture, it is good to remember that the sharpest results for most lenses are found around two or three stops below their maximum aperture. Especially cheaper lenses can give very bad results at full aperture.
An auto-exposure mode where you select the required lens aperture and the camera sets the necessary shutter speed, to give the correct exposure based on the auto meter reading. This mode is ideal for landscape and still-life photography where maximum depth-of-field is required. It's either indicated on the camera as AP (aperture priority) or AV (aperture value).
Called 'extender', 'lens extender' or 'telephoto extender' by some manufacturers. (Not to be confused with an 'extension tube'!). A teleconverter is an accessory that fits between the camera lens and body to increase the focal length of a lens by 1.4x, 1.7x, 2x or 3x. When coupled with a 200mm lens, for instance, teleconverters would give these results: a 1.4x teleconverter gives an effective focal length of 280mm, while a 1.7x teleconverter increases this to 340mm, a 2x teleconverter to 400mm and a 3x to no less than 600mm. Teleconverters are compatible only with selected lenses, so always check with the manufacturer or retailer before buying. Although they will work with some zoom lenses, they're best used with (fast) prime lenses, since there usually is a drop in quality, and many prime lenses give a higher level of quality to start with. Besides changing the effective focal length, the effective aperture of the attached lens is increased by one or more stops as well. Autofocusing usually does not operate if the effective maximum aperture is greater than f/5.6 with the lenses/cameras from most manufacturers (in some cases greater than f/8, like on the Canon EOS 1V and EOS 3 cameras). And not all teleconverters support autofocus in the first place!
This is the eye of the camera and is used to capture the image it sees onto the camera's light sensitive film, or CCD in digital camera. The size of lens is measured and indicated as a focal length. Cameras come with either a fixed lens or zoom lens with a range of focal lengths (see lens range) and on some SLR and rangefinder cameras the lens detaches so others can be attached to increase versatility. With a detachable lens camera it's often possible to buy just the body with a lens of your choice.The amount of light passing through the lens is controlled by an aperture, which is often quoted with its maximum aperture setting.Buying adviceSLRs: If you intend buying a specific lens in the future make sure that it's available in the same mount as the camera you are considering or own. Also if you're upgrading cameras, buy one with the same lens fitting or one that can be adapted to save the cost of replacing all the lenses you own.Digital and compact cameras: A fixed lens camera can often be much smaller so could be selected if you need to travel light. It's also less expensive if your budget is tight. It's better, though, to choose a camera with a zoom if you can afford to, rather than using a digital zoom or cropping the picture later. Go for one with a wider angle zoom if most of your pictures will be landscapes, interiors or family group shots.Choose a version with a longer telephoto setting if you want to shoot long distance subjects, portraits and wildlife.
(Not be confused with Fixed focus lens!) A lens that only has one focal length (as opposed to a zoom lens). A fixed focal length lens (also called 'prime lens') will often have good brightness, contrast, and be optically well-corrected. For that, it doesn't need any special glass or aspheric lens elements. Fixed focal length lenses are always superior to zoom lenses if they're made with the same optical materials and standards. They usually offer a wider maximum aperture than zoom lenses. They're often preferable for indoor shooting, but are also favourite choices as long telephoto lenses used for wildlife, sports and news photography.