Flash is an extremely bright light of exceptionally short duration. It is important to note that there are only three main kinds of flash although there are many different makes and sizes.

Manual Flash

A manual flash will give out a fixed amount of light each time it is fired. You calculate the correct exposure by first estimating the distance between the flash and the subject. Looking this distance up on the back of the flashgun will give you the correct F-stop which you have to set on your camera lens.

Automatic Flash

An automatic flash is usually more expensive than the manual flash as it has the advantage of having a Thyristor that reads the amount of light reflected from the subject and cuts off its power when the exposure becomes sufficient based on the given aperture and ISO that were previously set by the user.

Dedicated Flash

Dedicated flashguns are designed to work according to the information provided through the electrical contact in the mounting bracket between the camera and the gun. In which the TTL (through the lens) metering system is used to make the exposure reading, instead of the Thrystor.