E X P O S U R E

This weeks class was heavily based on exposure, and the tools used to achieve the correct exposure of an image.

Exposure depends on:
*ISO rating
*Subject lighting (The level of illumination)
*Subject reflectance
*Your personal preference

Because of these variables an image can either turn out over exposed, under exposed or 'correctly' exposed.

As an ISO standard we can see that a doubling of the rating = a doubling of the sensitivity
So an ISO of 400 requires half the exposure of an ISO of 200!

Setting a high ISO = Image degradation so therefore we know we should use the lowest ISO in any given situation to avoid image quality being disrupted.

We also know that digital cameras use a sensor to convert light to an electronic signal, which can then be manipulated by amplifying the signal.

We can also gather that the higher the illumination the faster the shutter speed needs to be, with a small aperture for the image to be correctly exposed, likewise when the illumination is low, the shutter speed used can be lower with a wider aperture. This sort of slow shutter and aperture width may require the use of a tri pod to avoid camera shake.

We also discussed meter reading types such as;

* AVERAGE - the entire field of view is averaged.
* EVALUATIVE - interprets scene based on data base
* CENTRE WEIGHTED - the majority of the measurement comes from the center
* SPOT - majority of light measured in a small area