The opening of the lens is like the pupil in your eye… if you look in the mirror in low light, your pupil will be dilated (wide open). If you then turn the light on quickly, your pupil will quickly close down to a small opening. This is your eye on auto mode controlling how much light is entering the eye. The same is true for the lens of a camera… the larger the opening is, the more light it lets in and the smaller the opening, the less light it lets in. The aperture itself is made up of several overlapping metal blades that work together to increase the size of the opening or decrease it. There are several size openings called “f stops”. The most common ones are f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, and f/22.
The part of this that can be sometimes confusing is the fact that the smaller the f/number, the larger the opening in the lens… f/2 is very large opening where f/22 is a very tiny opening. If you can think of it in terms of fractions, 1/8 is larger than 1/16, then f/8 is a larger opening than f/16.
Every time you move from one f/stop to another, you either double or cut in half the amount of light that you have entering your lens. For example, if you change from f/11 to f/16, you just cut your light in half, and then to f/22 in half again… this is not as completely dramatic as it sounds (use the shutter speed with the change in aperture and you can completely control your light).
Now, here is the really neat part about aperture… it really affects the way the picture looks in the end. With the smaller numbered apertures (larger opening), you get a blurred background. With the larger numbered apertures (smaller opening), you get a more clear background.
When you see a close up picture with only a small section in focus (macro photography), then the photographer used probably f/2 or f/2.8. When you see the really nice landscape shots with everything in focus, the photographer probably used f/16 or f/22. Everything else sort of falls in the middle depending on how blurred or clear the background is.
Mastering Auto Modes:
We are going master the auto modes first and work our way to the manual modes. This week, we are going to take a look at Portrait Mode. When you put your dial on portrait mode, you are telling your camera that you want to use one of the small numbered f/stops (which is a large opening which makes the background blurry). Your camera will probably choose anything from f/2 (if the lens is capable) up to f/4 or f/5.6. It won’t choose f/11, f/16, or f/22 because this will make the background clear which is used in landscape mode (we’ll cover that one later). I think that the really small numbered f/stops like f/1.8 or f/2 are used in macro photography (looks like you used a magnifying glass to take the picture).
So, for this week, choose portrait mode and see how your camera reacts (if you are not sure which one on your dial is portrait mode, check your manual – mine is the profile of the lady – Nikon camera). If you are working in lower light, the camera will also choose to use a slower shutter speed… don’t be surprised by this. If the camera decides to keep the shutter open longer than you expected, you will probably get “camera shake”. Just use a tripod or place on a table or something to stabilize it. We’ll cover shutter speeds a little later. For now though we are trying to get a clear subject and a blurred background. This represents the lower end of the aperture scale.
Have fun with your portraits this week… remember, anything can be taken in portrait mode… not just people. It’s just more of a close up and blurred background.