ABOUT SHUTTER SPEEDS
The shutter speed used for each exposure is displayed on the data panel. The following notation is used:
The reciprocal is used for shutter speeds from 1/2000 second to 1/3 second. 125 is 1/125 second.
For shutter speeds of a half a second or longer, a quote mark is used to denote whole seconds. 1”5 is one and a half seconds and 15” is fifteen seconds.
WHAT IS AN ƒ-NUMBER?
An f-number indicates the relative aperture of the lens and lets us determine how much light it lets through. But why does the number get bigger when the amount of light decreases? The answer is in the way it is written, f/4.0, f/8.0. etc. That means the focal length of the lens (f) divide by 4 or 8. So a 100mm lens at f/4 has a 25mm effective aperture (100/4) and at f/8, a 12.5mm effective aperture (100/8). The f-number indicates the size of the aperture as a fraction of the focal length of the lens.
The f-number series was carefully chosen to make controlling exposures easy. In the chart, the aperture and shutter speed combinations give the exact same exposure. Notice how the shutter speed changes to compensate for the change in aperture.
f/2.8 
1/2000s
f/4.0 1/1000s
f/5.6 1/500s
f/8.0 1/250s
f/11 1/125s
f/16 1/60s
f/22 1/30s
f/32 1/15s
41 