Exposure Triangle
-aperture
-shutter speed
-iso
Focal Length vs. Viewpoint
f=18mm,35mmsensor, f=180mm, 35mm sensor
1st subject 0.5m away, 30m away
Changing focal length allow us to move back, and still capture the scene
Changing viewpoint causes perspective changes
Exposure = irradiance * time
H = E x T
Irradiance(E)
– amount of light falling on a unit area of sensor per second
– Controlled by lens aperture
Exposure Time(T)
– How long the shutter is kept open
Amount of time the sensor is exposed to light
shutter speed
usually denoted in fractions of a second(1/2000,1/1000,1/250,1/60,1/15,15,30,Bulb)
Irradiance on sensor -> the amount of light captured is proportional to the Area of the aperture(opening)
Area = π(f/2N)^2
f is the focal length, what is the diameter of the Aperture?
Aperture number gives irradiance irrespective of the lens in use
f/2.0 on 50mm lens -> aperture = 25mm
f/2.0 on 200mm lens -> aperture = 100mm
f2.8 4, 5.6, 8, 11, 16
More light, less light
area = π(f/2N)^2
Doubling N reduces A by 2C, and therefore reduces light by 4X
from f/2.8 to f/5.6 cuts light by 4X
ISO(sensitivity)
ISO100, ISO1600
Third variable in getting the right exposure
Film sensitivity vs. Grain(of film)
f156
shutter speed:1/10
