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Chapter VI Other Auxiliary Devices

Exposure meter

d

To get a good image, the surface of the film must be exposed to the appropriate amount of exposure by: To light. And it is done.

Exposure tables included with each film you buy: These tables give good results in the standard cases mentioned in the table, but when there are any differences in light, they cannot be relied upon.

A built-in light meter in the camera: There are several types:

(a) A type based on a Selenium cell: it works without a battery, and this type gives good results in strong and medium light with standard lenses, and since the exposure is measured without going through the lens, and therefore it does not give good readings, telephoto or wide-angle. with lenses with

(b) A type based on a cadmium sulphide cell: this type requires a battery and measures the light through the lens. This type is more sensitive than the previous type and can be used with any lens. The disadvantage of this type is slow measurement in weak light, as well as memory
It stays entangled in little other strong lighting ie for a period of up to several

minutes . Gallium (c) is a type based on Silicon blue cell or galllum arsenide: this type is very sensitive and closer to eye sensitivity. There is a type that measures the light falling on the film during the exposure, as well as the flash light falling on the film, such as the one in

Olympus OM2 camera

These types are excellent in general, but they are only suitable for measuring contrast in parallax

hardly. Separate scales: These are of several types:

(a) Reflected light exp-meter: This type measures exposure from the location of the camera and has the same types and works in the same way as the type built into the camera except that it cannot use different lenses except with special increments.
(B) Incident light exp meter: This type is placed in the place of the subject to be photographed and directed towards the camera. This type gives a more accurate measurement as it does not deceive the colors or shades of the subject, but it cannot measure the contrast of the subject. Also, sometimes it cannot be used, for example, when photographing a predatory animal.

These two types measure light in the subject area and give an integrated reading for all subject areas.

Rays reflected from area (c) Spot meter: This meter has a very narrow reception angle, about 1 to 20, and with it a very limited measurement can be made of the subject to be photographed. It is possible by this scale to measure the degree of contrast of the subject. This type is difficult to use except in the hands of experienced experts, and in this case it is given the best measurements

(d) Flash meter: This, as the name indicates, is used to measure flash illumination. Usually, the amateur is satisfied with the type built into the camera. And when his experience increases

He will need another type depending on his needs

Batteries

Electronics entered the world of photography in an amazing way, as most devices are powered by electronic circuits that need batteries. Therefore, it is necessary to know information about this important part.

Batteries work with a chemical reaction that turns into an electric current. There are many types of batteries that will mention the most important types that enter the world
Fixed . Its defect is that we do not know the battery life by measuring the voltage difference, as we may find it normal, and suddenly, after a few minutes, we find the voltage difference is zero.”

Nickel-cadmium batteries: They are sold uncharged, and they are charged in their own charger according to the period determined by the manufacturer of the device. Charge it immediately before use, because it loses most of its charge within two weeks.. Keep the batteries empty and do not recharge a battery that is still partially charged to extend its life.