Get your aperture right, and you may get mucho better pictures! Now what is Aperture really? OK, I think I recall there is (or was) even a famous fine-art photo magazine called “Aperture“. So, it seems to be an important concept in the field of Serious Photography.
Wikipedia says: “In optics, an aperture is a hole or an opening through which light is admitted… Obviously, the aperture also determines how many of the incoming rays that are actually admitted and thus how much light that reaches the image plane.”
Well, Wikipedia has got it spot-on, as usual. You use a large aperture, ie. a large hole, and lots of light streams in. You use a small aperture… what do you think happens? Right, less light gets through during a set amount of time! One detail to remember: in your camera, large apertures have small numbers and vice versa, like f=2 is a large aperture and f=8 is a small one. Expensive, “fast” lenses are capable of large apertures. OK, I guess we could stop here and let you figure out the rest yourselves…
Still there? OK, the thing about aperture is to get control over how you use it in your photos. You see, if you use a large aperture, the depth of field is small - and conversely: small aperture equals large depth of field.
This is the important thing to know about aperture. Maybe I should add a few words about what depth of field is. Think of it this way: You focus the camera on something, say a flower in a field. Usually, not only that particular flower will be rendered sharp in the picture, but also some of the flowers closer to the camera as well as some of those further away.
This is the phenomenon called “depth of field”. Just how much of it you will get in each case depends on several factors, but the main ones are your distance to the subject and your aperture setting. Assuming you have already chosen a distance that you like, you can now adjust the depth of field by playing with the aperture setting.
Do you have a somewhat distracting background which you’d rather get rid of? OK, try using a large aperture to put that pesky background out of focus! Since the depth of field is now smaller, everything that is significantly further away from the camera than the subject you’re focusing on will be rendered blurry - and hopefully less distracting.
Obviously, if you use a larger aperture you need to change one or both of the two other points in the Exposure Triangle - shutter speed and ISO-setting. You will need to use a faster shutter speed and/or a lower ISO-setting to avoid having the picture over-exposed to light. Complicated? Not at all - I’m pretty sure there is some setting on your digicam which takes care of this automatically. Like, you set the aperture you prefer and the camera takes care of the rest. If in doubt, consult the manual…
Now, suppose you are snapping a picture of something and you want all of it in focus - what do you do? Right again! - you use a SMALL aperture setting. Like the photo of the spiral staircase here, note how all of it is rendered sharp, even the knob in the lower-right corner which seems quite close to the camera.This is how you play with aperture to control the depth of field in an image.
Before closing, I like to give you another short photo tip: You need to remember that the camera’s autofocus always thinks whatever is in the center of the picture is also the thing to focus on. This is by NO means always the case, as in the staircase case here. The photographer wouldn’t have managed to get everything sharp if he had put the focus on the most distant part of the picture - which is in the center. Instead, he must have focused on some point about half-way up the stairs, to get this splendid result.
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