Photography is all about light. Three controls affect the amount of light reaching the camera’s sensor: aperture, shutter speed and sensitivity. Each one also has a creative impact on the image.
ApertureAperture is a fancy word describing the size of opening on the lens. Aperture is denoted in f-stops. |
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| aperture size | light effect | creative effect | uses |
| smaller aperture (larger f#) smaller opening |
less light reaches the sensor | narrower depth of field – less of the photo in focus | separate a subject from a distracting background, portrait, close-up (macro), |
| larger aperture (smaller f#) wider opening |
more light reaches the sensor | wider depth of field – more of the photo in focus | landscapes, crowds |
Shutter SpeedA camera’s shutter is like a curtain that opens and closes in front of the sensor. It determines how long light reaches the sensor. Shutter speed is measured in seconds or fractions of seconds. At slower shutter speeds, use a tripod to prevent camera shake and the resulting blurry images. |
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| shutter speed | light effect | creative effect | uses |
| faster shutter speed | less light reaches the sensor | freezes motion | clear shots of sports, kids, animals, objects in motion |
| slower shutter speed | more light reaches the sensor | blurs motion | dreamy shots of moving water, low light shots, fireworks, night shots |
SensitivityThe sensor’s sensitivity to light is measured in ISO. |
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| ISO | light effect | creative effect | uses |
| lower | sensor is less sensitive to light, | sharper, more detailed image | daylight outdoor shots |
| higher | sensor is more sensitive to light | less detail is captured resulting in more digital noise (grain) in image |
high speed sports, action, low light situations |
And now for the fun bit. Some smart folks have divided each of these three controls into “stops” as shown in the following table. Each stop up doubles the light. Each stop down halves the light. This allows the photographer to change the creative effects while maintaining equivalent exposures.
| aperture (Av) | shutter speed (Tv) | sensitivity (ISO) | ||||
| exposure | f-stop | depth of field | seconds | motion | ISO | image quality |
| brighter | f 1 | shallow | 1 | blurred | 12800 | more grain |
| f 1.4 | 1/2 | 6400 | ||||
| f 2 | 1/4 | 3200 | ||||
| f 2.8 | 1/8 | 1600 | ||||
| f 4 | 1/15 | 800 | ||||
| f 5.6 | 1/30 | 400 | ||||
| f 8 | 1/60 | 200 | ||||
| f 11 | 1/125 | 100 | ||||
| f 16 | 1/250 | 50 | sharp | |||
| f 22 | 1/500 | |||||
| darker | f 32 | deep | 1/1000 | frozen | ||
The following four images have equivalent exposures.
| aperture (Av) | shutter speed (Tv) | sensitivity (ISO) | ||||
| base image | f 5.6 | 1/250 | 200 | |||
| image 2 | f 8 | ½ light | 1/125 | 2x light | 200 | |
| image 3 | f 4 | 2x light | 1/250 | 100 | ½ sensitivity | |
| image 4 | f 11 | ¼ light | 1/125 | 2x light | 400 | 2x light |
With the above tools and some knowledge of artistic composition, you are on your way to great photos. Now go and have some fun!
