7. How to Take Photos 2: Aperture
Almost all this information comes from lessons by Chris Parker and Chris Bray, including the photo examples.
Aperture (the size of the hole in the camera’s diaphragm) controls depth of field, which is the amount of space in the image that will be in focus (sharp, crisp). A shallow depth of field keeps only one precise distance in focus:
A large depth of field shows everything in focus:
Aperture can be difficult to learn because it isn’t intuitive – you can’t see the difference when you look through the viewfinder. You just have to get to know what the different numbers do, when you change the setting – through practice. You should also know, your aperture setting isn't the only factor affecting depth of field. It also depends on your distance from the subject, your subject's distance from the background, and the type and length of the lens you use. Every lens will have a different minimum and maximum F number. In fact, some people are willing to pay thousands of dollars more for a lens that's almost identical to a cheap lens, but with a lower F number:
Aperture is measured in F numbers, the F referring to "focal length". The bigger the number, the smaller the hole, and the longer the exposure must be. With the smaller the number, the larger the hole, and the shorter the exposure time needed.
Remember, for smaller depth of field, use a smaller F number. For larger depth of field, use a larger F number. Don’t worry about what the hole looks like, just remember small for small and large for large. F22 and 32 are pretty large, so you’ll get more detail in a big depth of field. At F2, you’ll have a very small depth of field, meaning anything in front or behind the subject will be blurry. Things close to you may be blurred out completely. This is great for annoying things that get in the way of your shot, like a fence at a zoo:
In general, a shallow depth of field is better for portraits, because you don't get distracted by details in the background. Which of these emphasizes the person better?
and a large depth of field is generally better for landscapes, when you want to see all the background details:
Using a shallow depth of field is a very powerful compositional tool to force viewers to focus on what you want – mastering aperture really helps make you a more professional photographer. When you master this, you will find that blurry areas of your image form little circles of light. These are called bokeh, and can be quite beautiful. Different lenses form different bokeh shapes.
For landscapes, even with a high depth of field, try to focus primarily on what’s near you – far objects will still be well in focus. But, if you focus on what’s in the background first, what’s in front will be blurry. If you want a really sharp, in-focus landscape image, the aperture will be so small (the F number so big) it may need a longer exposure, in which case you may need to put the camera on a tripod.
If you try a very large F number in low lighting conditions, the shutter speed (that you see through the viewfinder) will start flashing (usually at around 30 seconds or so). This is warning you that there isn’t enough light to get a good exposure at that aperture setting. So, when it’s flashing, that’s bad. Same with too much light. If you photograph the sun, even at the fastest shutter speed, you might see it flashing because it’s too much light coming in, and the camera knows it’ll be over exposed – so it warns you by flashing. If you take a shot while the shutter speed is flashing, the photo will be either underexposed or overexposed, depending on the light. In general, if you adjust the aperture one way and the shutter speed the other way, you can come to a compromise point where the numbers will stop flashing and you'll get a good shot.
One thing to note, when you use a large F number, and take a shot with the sun in it, you’ll get a beautiful starburst pattern of light from the sun – showing rays of sunshine (this may vary from lens to lens).
Comments
Post a Comment