underwater Photo Course :: (1) The Basics :: Film Speeds Primer

As if it weren't enough to take in that you had to get the right exposure by metering and setting apertures and shutterThe shutter is an integral part of all cameras. It opens to allow light through. The greater the range of shutter speeds a camera has the better. speeds you also have to take account of the film sensitivity - also known as film speedFilm speed is the measure of a photographic films sensitivity to light. Like shutter speeds a doubling of film speed means a difference of one stop. In reality you are stuck with the speed of your film (unless you push processa development technique that increases the speed of the film being processed it later).

Many digital cameras can emulate of film speeds by allowing adjustment of sensitivity (speed ratingthe speed rating for digital cameras depending on the sensor sensitivity the sensor noise and the appearance of the resulting image). Some housings allow you to do this underwater.

The usefulness of being able to adjust speed is that you can shoot in lower light. Unfortunately there is a trade off in picture quality by an increase in noiseNoise is a random pixelation across the image. This appears like a TV picture when the set is switched on but not tuned in! Dust and scratches can also be described as noise., artefactsSpurious effect or object appearing in an image due to defects in the collection processing or display of an image, and grain(AKA granularity) is the unwanted random optical texture

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