Understanding Exposure - ISO, Aperture and Shutter Speed Explained. What controls exposure?
ISO ratings determine the image sensor’s sensitivity to light, each value of the rating represents a “stop” of light, and each incremental ISO number (up or down) represents a doubling or halving of the sensor’s sensitivity to light. The Aperture controls the lens’ diaphragm, which controls the amount of light traveling through the lens to the film plane. The aperture setting is indicated by the f-number, whereas each f-number represents a “stop” of light.
The Shutter Speed indicates the speed in which the curtain opens then closes, and each shutter speed value also represents a “stop” of light. The shutter speed is measured in fractions of a second. Most Popular Photography Tips, Tricks, and Hacks of 2010. Spot Metering. By Vadim Makarov for his Photo Pages When a photographer describes how he set exposure to photograph a scene, he usually says something like "I spotmetered her face and opened up one stop.
" The problem with this description is that I often base my decision on several meter readings and don't follow this way of operation. Instead, I set the aperture and shutter speed in the manual mode and check where the meter readings off different objects fall. My Canon SLR camera displays an exposure scale in the viewfinder.
Viewfinder of Canon EOS 500N during partial metering in manual mode.