PRACTICAL DV FILMMAKING

Practical DV FilmMaking

• Overview
• Inside video
• Films and how they work
• Pre-production
• Production tools
• Production aesthetics
• Post-production tools
• Post-production aesthetics
• Careers and distribution
• Mapping the industry
• Glossary of film and video terms

When light passes through the lens it hits a shutter that is opening and closing 25 times each second (in PAL standard cameras for the UK), or 29.9 (NTSC) for North American cameras. Each of these images that gets recorded is called a frame. The camera can alter the speed at which it opens its shutter, even though it still opens it the same num­ber of times each second. The minimum speed for many cameras is 1/50th of a second, with the max­imum in consumer level cameras around 1/8000th of a second.

The difference between these is most evident when you record fast-moving objects. In 1/50th of a second, the length of time a shutter is open, the object (let's say a car) travels a long way in front of the camera in one frame (let's say 20 feet), and therefore blurs all the movement within that distance onto one frame. If you up the shutter speed to 1/1000th of a second, then the shutter is open

for only a fraction of that and records only a fraction of the movement, say one foot, resulting in no blurring.

However, there is a knock-on effect in reducing the amount of time the shutter is open; less light can enter the lens. So it is kind of doing what the iris does in keeping some of the light out. If your camera has manual controls then it will be straightforward to adjust both the shutter and the iris to make sure that enough light gets in to give a full, clear picture. You can also use shutter speed and iris settings to give a darker and more jagged effect to a movie. In 28 Days Later (Danny Boyle), a high shutter speed in this digitally shot film gave it a spooky look, in keeping with the post-apocalyptic scenario and help­ing the large number of action shots by preventing blur.

So far so good, but the iris and shutter can play other roles too. If you reduce the hole in the iris then the range of objects that are in focus is altered too - this is called 'depth of field'. If you think of a line of trees in an avenue with you standing with your camera in the middle of the road, not all of them are going to be in focus all the time. If you were to adjust the iris to let less light in, making the hole at the front smaller, then there would be more of the line of trees in focus. If you were to open the iris, then less of them would be clear.

It makes sense, then, to think about these three aspects of a shot - focus, iris and shutter - as being linked and needing a joined-up approach to dealing with them. When shooting, if you adjust one of them, think about how it affects the other two.