This is the sixth in an on-going series of articles on photographing miniatures, in which we’ll learn some basic rules involved in getting the correct exposure. This article is rather technical, for which I apologize in advance, but it’s necessary to understand the basics of how exposure works before we can get to some other important elements of photographing your mini.
Exposure Settings: The Aperture
Inside your camera lens, there is a disk which is actually composed of eight or so flat pieces of metal (called “leaves”) which overlap one another to form a circle. These leaves slide toward the center of the lens or outward, narrowing or widening the circular opening in the middle of the circle that they form. This opening is called the aperture, because it’s the hole (aperture or opening) which permits light to pass through the lens and into your camera.
Basically, you can adjust how big that hole (aperture) is, thus controlling how much light hits the “film” inside your camera. This is done using the aperture setting dial on your lens–that’s the dial with the weird numbers like 2.8, 5.6, 11, etc. (Or at least it used to be. In the digital age, many lenses no longer have the numbers on the “barrel,” the outside housing–they’re controlled through the camera.) These numbers are expressed with a lower-case f in front of them, standing for “focal point.” (Too technical to get into here, but it will come into play in the next article when we discuss depth of field and focus.) Thus, f8 means the aperture setting of 8. Easy.
First basic rule of thumb: the smaller the number on your aperture setting, the larger the aperture, which means the larger the hole, which means more light is coming in. I know it’s counter-intuitive; those numbers actually mean something, but this is technical enough without getting to that level. Just memorize this basic fact: smaller number = more light.
First basic rule corollary: Each click of the aperture setting adjusts the light by a factor of two. That means that, if you open the aperture one setting (moving to the next smaller number–f11 to f8), you double the amount of light passing through the lens. Close it by one setting (moving to the next bigger number–f8 to f11), and you halve (cut in half) the amount of light.
This is a trifle confusing because the numbers don’t seem to be related to one another. One would expect the light to be cut in half when moving from 8 to 16, since those numbers are related by a factor of 2. But moving from 8 to 16 actually cuts the light to one-fourth–or four times as much when going from 16 to 8. The numbers go in two sequences rather than one: 4, 5.6, 8, 11, 16, etc. (Sort of like a question on the SATs: “What is the next number in the series?” Answer: 22.)
Exposure Settings: Shutter Speed
The next element of exposure is how long your shutter stays open. To avoid confusion, understand that the shutter is not the same as the aperture. The aperture is inside the lens, controlling how much light passes through it; the shutter is inside the body of the camera, controlling whether or not that light enters the camera in the first place. The shutter works like a sliding door that’s normally closed. Press the shutter release, and that door slides open for a fraction of a second, then slams shut.
And fractions of seconds is exactly what shutter speeds are measured in. They start at 1 second, then proceed in halves from there. Thus, typical shutter speeds are 1, 1/2, 1/4, 1/8, 1/16, 1/32, 1/64, 1/125—oops! It’s true: the halving gets fudged at 125, just for simplicity I guess. Regardless, these speeds don’t generally include the “1/” portion of the number (is that a numerator or a denominator? Hamblin would know), and are written simply as 16, 32, 64, 125, etc.
Second basic rule of thumb: Smaller number = more light. Yup, same as with the aperture. Makes these rules easy to remember–or easier to screw up both shutter and aperture. The basic premise is actually pretty simple if you start from 1 second and work forward: a shutter open for 1 second admits twice as much light as when it’s only opened for 1/2 second. It’s easy to forget this, however, when you’re shooting at 125 or 250–as you generally will be.
Aperture and Shutter Work Together
The final thing to understand is this: Correct exposure is determined by how much light is admitted into the camera and how long it’s admitted for. Not grammatical, but accurate. Just remember: How much + how long = exposure.
And here is our third rule of thumb: Restricting the amount of light passing through the lens (via the aperture) requires that we admit light for a longer period of time (via the shutter). If that’s not easy to remember; try this: If you move the aperture one click, move the shutter one click in the opposite direction. Closing the aperture one setting (larger number) cuts the light in half, so we must make the shutter one click slower (smaller number), thus leaving the “sliding door” open longer. Change the aperture from 8 to 11, change the shutter from 250 to 125. It’s more intuitive and simple to do than it is to explain.
This is a Bunch of Useless Information
“Why are you filling my head with all this techno-mumbo-jumbo about f-stops and shutter speeds,” you ask, “when my camera does it for me automatically?” Because you cannot permit your camera to do it for you, that’s why–you must learn to do it manually if you want to retain control over things like depth of field, correct exposure, color balance, and all sorts of stuff.
“I knew I should have kept my point ‘n’ shoot and not bought this stupid SLR!” Yes, I did mention in my very first article that many people avoid SLR cameras because they expect you to be smarter than the camera. But you are, you just don’t know it yet. Just grasp these two fundamental rules:
- Correct exposure = aperture + shutter
- Changing the aperture requires an equal change in the shutter–in the opposite direction.
The aperture in the lens determines how much light passes to the camera, and the shutter determines how long that light is admitted. If you cut that light in half (one aperture setting), you must admit it longer (one shutter setting). In our next article, I will explain why this matters in determining what is in focus in your image.
Next Article: Depth of Field (or, How to Photograph Groups of Miniatures)