Camera Exposure Basics

Mike from thesubstream pompously expounds on the basics of lenses and exposure.

You know, there is 8 millimeter, there is super 8, there is double super 8, there is 16, there is super 16, 35, super 35, iMax, there is CMOS and CCD, there is Fischer-Price Pixel Vision, there is HD, HDV, mini DVD cam, there is VHS and Beta, there is Beta cam, there is Beta cam SX and there is DigiBeta, but it’s all basically the same thing. It’s light, a handsome dude, a lens with an openy closey aperture in it, a camera with a shutter that opens and closes wippy skippy like a billion and a half times a second and film or video stock which takes the light that comes from the sun that bounces off your handsome dude, goes through the lens with its openy closey aperture through the wippy skippy like a billion and a half times a second shutter and eventually crashes into a pile of silver hay light crystal and emulsion or a magnetizable piece of plastic. And eventually further on down the line, magically, it becomes an image. But all of that knowledge and a dollar will buy you a shitty cup of coffee because everything I’ve described so far is mathematical equation where all the variables, the sun, the aperture, the shutter and the film stock are just that variable. And the only thing you won’t know in advance is what you want to be and result to be. In this case, well-exposed image of a handsome young man. So how do we get from here to there? As with anything that’s complicated either technical or theoretical, I find it easiest to understand by imagining a metaphor like a bucket. The bucket in this case is your film stock, or these hands that are inside your video camera. It can be an ISO speed bucket, it can be the sensor of the camera with the gain set to 0, 6 or 3 decibels. It doesn’t really matter because all you’re changing when you change those things is the amount of photons that you’re going to need to create a properly exposed image. And in this case, it’s 5 photons. The next thing is the shutter which opens and closes, wippy skippy like a billion and a half times a second alternately allowing and preventing light from passing through, and it can do that in a 16th of a second or a 500th of a second or in however long that is. Now assuming you’re not shooting a movie with a pinhole camera, your camera is going to have a lens hanging off the front. And all maths aside, lenses do two jobs. They focus the light coming in onto the film and they control the amount of it that passes through the aperture, which a fancy word for hole. It can be a big one, wide open, I guess 1.4 or closed down and small like F22 or average and right in the middle like F8. Now this, this is no bucket. This is a panaflex or an aeroflex or a bowlex. It’s a Pruder’s Balin Howell’s Pneumatic and it’s Michael Mann’s Viper Film Stream HD Cam from Miami Vice and Collateral. It’s film or video shutter and an aperture. And all that we need to create a properly exposed image is photons. Of course, there’s more to taking a good looking picture than just getting the exposure right. Changing the speed of your film stock or the angle or speed of your shutter or the gain on your video camera will affect the quality of your final image. And change the aperture in your lens will affect focus and depth to field. And assuming that you’re not using a box full of plastic balls as your light source, you’re going to be able to control that as well. Taking a good picture is as complicated as you want to make it. But in every camera ever since the beginning of time since cameras are invented thousands of years ago by a guy on Wikipedia, they’ve all been basically the same thing. Film or video, shutter, aperture, a handsome fellow, and a light source. Now stay tuned for our next video which will be on fixing an under exposed image imposed because I’m not doing the ball drop thing again.