ISO
ISO- (stands for International Standards Organization)- it is the Film speed or the sensitivity of the sensor.
25,50,100 are considered slow ISO's
200 to 400 are considered optimum
800 to 1600 are considered fast
A slow ISO absorbs light more slowly.
To put this in context Landscape photographers tend to use the slower ISO's and Sports photographers tend to use faster ISO's.
Slower film speeds historically allow for high definition.
High ISO speeds allow for low definition.
ISO controls 2 things- 1. Speed of the sensor in relation to how it absorbs light (light absorbtion).
2. The levels of definition (levels)
This gives us creative control.
Intensity
This refers to the Aperture, it controls the intensity of light falling on the sensor- brightness of light (widening of the parameters of focus).
F2.8 4 5.6 8 11 16 22
High Intensity Low Intensity
Aperture controls 2 things- 1. Intensity of light falling onto the sensor
2. Depth of field
Time
Time= Shutter speed
Examples would be- 1/2 1/4 1/8 1/15 1/30 1/60 1/125 1/500 1/1000
This controls the amount of time that the light is allowed to spill onto the sensor.
Shutter speed controls 2 things- 1. Time allocated for light to fall on the sensor.
2. Subject movement (to freeze action)
Camera
Incident Light- this is the light that falls onto the subject
Reflective Light- is the light that reflects off a subject- this is what the camera measures)
It is always best to measure incident light for a portrait.
It is useful to remember that more than 2/3 of the cameras ability/memory is dedicated to the light greys and highlights, this is why it is best to 'shoot to the right'.
By getting the exposure correct it gives more lattitude for image manipulation- post production freedom. If an image is underexposed you loose detail in the highlights.
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