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Batteries

Admin — Sun, 17 Apr 2011 11:10:50 +0000

Digital cameras have high power requirements, and over time have become smaller, resulting in an ongoing need to develop a battery small enough to fit in the camera and yet able to power it for a reasonable length of time.

Two broad types of batteries are in use for digital cameras.

AA, CR2, or CR-V3 batteries :
The first type of battery for digital cameras conform to an established off-the-shelf form factor, most commonly AA, CR2, or CR-V3 batteries, with AAA batteries in a handful of cameras. The CR2 and CR-V3 batteries are lithium based, and intended for single use. They are also commonly seen in camcorders. AA batteries are the most common; however, the non-rechargeable alkaline batteries supplied with low-end cameras are capable of providing enough power for only a very short time in most cameras. They may serve satisfactorily in cameras that are only occasionally used.

Consumers with more than an occasional need use AA Nickel metal hydride batteries (NiMH) instead, which provide an adequate amount of power and are rechargeable. NIMH batteries do not provide as much power per volume as lithium ion batteries, and they also tend to discharge when not used. To get same power, NiMH Rechargeable battery takes up to two times in volume compare to Li-on Rechargeable Battery, by weight NiMH Rechargeable Battery is three to five times heavier, but by price NiMH Rechargeable Battery is only a half compare to Li-on Rechargeable Battery. Please see Wikipedia: Table of rechargeable battery technologies in Rechargeable battery. They are available in various ampere-hour (Ah) or milli-ampere-hour (mAh) ratings, which affects how long they last in use. Typically mid-range consumer models and some low end cameras use off-the-shelf batteries; only a very few DSLR cameras accept them (for example, Sigma SD10). Rechargeable RCR-V3 lithium-ion batteries are also available as an alternative to non-rechargeable CR-V3 batteries.

Lithium Ion Batteries :
The second type of battery for digital cameras is proprietary battery formats. These are built to a manufacturer’s custom specifications, and can be either aftermarket replacement parts or OEM. Almost all proprietary batteries are lithium ion. While they only accept a certain number of recharges before the battery life begins degrading (typically up to 500 cycles), they provide considerable performance for their size. A result is that at the two ends of the spectrum both high end professional cameras and low end consumer models tend to use lithium ion batteries.

Autofocus

Admin — Sun, 17 Apr 2011 11:09:32 +0000

An autofocus (or AF) optical system uses a sensor, a control syst em and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication.

AF Servo

Admin — Sun, 17 Apr 2011 11:08:15 +0000

Halts auto focus operation once the subject is in focus and is useful when shooting a subject outside the focus area in the viewfinder. The photographer should first lock the focus with the subject inside the focus area, then recompose the shot as desired.

AF Assist Illuminator

Admin — Sun, 17 Apr 2011 11:06:42 +0000

Auto focus systems require sufficient light and contrast to operate effectively. An AF assist illuminator provides the necessary light and contrast, when ambient conditions are not sufficient for auto focus operation. AF assist illuminators generally operate automatically, without requiring any additional action by the photographer. The AF assist illuminator’s light will not appear in the picture. This is a useful feature for photography in very dim light or total darkness.

AD Converter

Admin — Sun, 17 Apr 2011 11:05:32 +0000

An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device which converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement. The reverse operation is performed by a digital-to-analog converter (DAC).

Typically, an ADC is an electronic device that converts an input analog voltage or current to a digital number proportional to the magnitude of the voltage or current. However, some non-electronic or only partially electronic devices, such as rotary encoders, can also be considered ADCs.

The digital output may use different coding schemes. Typically the digital output will be a two’s complement binary number that is proportional to the input, but there are other possibilities. An encoder, for example, might output a Gray code.