1. Exposure *Controlled by Aperture & Shutter
*Shutter is diaphragm inside back of camera that opens and closes to allow light to reach film
*Shutter speeds are marked in seconds
Slower speed = more exposure faster speed = less exposure
* B setting on shutter stays open as long as shutter release button is held down. Longer time than on scale above.

2. Exposure
Each shutter is half the preceding one. It changes by a factor of 2 each time we move the shutter speed dial. Ex. 1/125 is half the exposure of 1/60
Aperture= iris type diaphragm with variable openings.
F stops = settings along the control ring. Mechanism which controls the aperture size.
Scale:
More exposure= “opening up” Less exposure= “closing down”

3. Exposure
Changing one step on scale changes film exposure by a factor of 2. Ex. F 5.6 gives twice the exposure as f 8.
When aperture is moved one step and exposure is changed (by a factor of 2) it is called one stop in exposure
Opening up one stop= Doubling exposure
Closing down one stop= Halving the exposure
Settings on aperture ring are designated as f -stops.

4. Exposure Exposure can be doubled in 2 ways:
1. Move f-stop to next smaller f-stop #. Ex. f 5.6 to f 4)
2. Move shutter speed to next smaller # (next slower speed). Ex. 1/250 to 1/125
Exposure Increments:
One stop= 2 times the exposure
Two stops= 4 times the exposure
Three stops= 8 times the exposure

5. Exposure
Equivalent Exposure Settings: a set of pairs of shutter speed & f-stop settings which produce the same exposure.
Ex. F 8 / 1/60= f5.6 / 1/125
This is because f5.6 is twice the exposure of f8 but 1/125 is half the exposure of 1/60, so therefore they are equal exposure.
It is important to understand equivalent exposures when you are considering depth of field and film speeds.
Reciprocity= The equivalent film exposure pairs also produce equivalent density on film. Follows same conditions as above in the equivalent example…..HOWEVER! It fails to produce equivalent density with long or very short exposure times. Gives less density. Can be corrected by changing exposure time or aperture.