Light (1)
| What's the most
important consideration when taking pictures? LIGHT! First of all, without light
there is no picture. Second, light can create the most stunning effects. Let's
start with a few fundamental principles. Aperture and shutter speed. To get light onto the film, you have two key controls. One controls the lens opening (aperture), the other one controls the shutter speed. Apertures are measured along a scale such as 1.0 - 1.4 - 2 - 2.8 - 4.0 -5.6 - 8 ... The numbers refer to a ratio, namely the ratio of focal length to (effective) lens width. Notice that the ratios increase always by the factor x 1.4 (e.g., 5.6 = 1.4 x 4.0). Without going through the physics, this means that each smaller lens opening reduced the light intake to 1/2. Shutter speed also go in halves (how convenient). For example, speeds might be 1/4s - 1/8s - 1/16s - 1/30s - 1/60s - 1/125s - 1/250s ... As a result, if the correct film exposure is 1/125s at 8.0 aperture, 1/250s at 5.6 is also correct, and so is 1/1000s at 2.8. That's extremely useful. Faster speeds are good for scenes where there's lots of movement. So, how much light does a picture need? That depends on the film of course. Sunny-16 Rule. Your camera most likely will select the aperture and or speed for you, or you have a meter to do that. But if not, there's the Sunny-16 Rule. The name gives it away. If it's sunny outside, use aperture 16. OK, but what shutter speed? Look at your film. If you have a 100 speed film, set the shutter speed to 1/100s (actually, use 1/125s). If your film is a 200 speed, set the shutter speed to 1/200s (actually 1/250s). Simple, but it works. Sunny with clouds - 11, cloudy but bright - 8, cloudy and dark - 5.6, deep shadow - 4, close to sunrise/sunset 2.8 or less. Inside, with bright artificial light, use 2.0 or 1.4. (c) Christian Wagner |