The first thing to understand in learning to use your camera outside of it’s auto setting is that 3 things control exposure (level of light).
1. The ISO (another lesson)
2. The shutter speed (also another lesson)
3. The APERTURE (AKA the hole in your lens) which is the topic for today.
Aperture settings are a number with an ‘f’ in front, e.g. f 2.8 or f 16. The tricky thing to try and remember is that the lower the number, the more light that gets to your camera. Take a look at the image below. At f 2 the hole is wide (lots of light) but at f 16, it’s very narrow (much less light).
The degree of aperture that you have to work within (lowest to highest) is based on your lens, NOT your camera. Generally, the more expensive the lens the lower the maximum aperture, that is, the more light it will let in and therefore work better in low light situations.
When you are looking at a lens it will either be a FIXED or a VARIABLE aperture lens. A variable aperture lens will be cheaper and you will see two aperture numbers on the lens. For example, a Canon EF 70-300mm f/4-5.6. When you are zoomed out at the widest (70mm for this lens) you can shoot with an aperture of 4.0. However, when you are zoomed all the way in you will only be able to shoot with an maximum aperture of 5.6. Compare that to a Canon EF 70-200mm f/2.8L which is a fixed aperture lens. It only has one number listed (f/2.8L) which means you can shoot at 70mm, 200mm or anywhere in between, at a maximum aperture of 2.8.
The other thing you will notice in your photos when you change your aperture setting is the depth of field.
Now take a look at the picture below.
When taking portraits, you often want to isolate your subject from the background by using the maximum aperture setting your lens allows. To do this, set your your camera to Aperture Priority mode, which will likely be ‘AV’ or ‘A’ on your mode dial. Then adjust the dial to the maximum aperture setting, i.e. the lowest number. Then focus on your subject (eyes if it’s a human) and click. Your camera will automatically adjust the shutter speed based on the amount of light available. Note: you should have your camera set to an ISO of 400 or lower while you are practicing.
The best way to really learn how this works is to get your camera, go outside where you have a good amount of light, set it to AV or A mode and take a series of photos. The subject doesn’t matter but for the purpose of learning choose a still object and either something close up or something with some distance between it and the background. Make sure you focus on the subject then take a series of shots, start with your maximum aperture, then dial it one click, take another shot, dial again, take another shot, keep going all the way to your minimum aperture. Watch how the shutter speed changes automatically as you adjust the aperture. Note, as your aperture number increases, less light will get in and therefore shutter speed will slow down to compensate. Once your shutter speed gets slower than around 1/60th of a second it becomes difficult to hand hold and you might get blurry images. Don’t worry to much about slight blur for this purpose. When your done, take a look at the images (on a computer is better) and notice how the background (or the stuff not in focus) gets more blurry as your aperture gets wider.
I can’t tell you how many times someone has asked me to help them figure out their “fancy” camera. It’s actually not an easy thing to do, especially in the few minutes most people think it is going to take. Firstly, you need to understand how a camera works and then the only way to master your camera is to try it and keep trying it. You won’t get there if you keep using AUTO mode or by using your camera twice a year. Commit to taking a picture (NOT in AUTO) every week or even every day if you can. Be creative, play with depth of field.
If you find this helpful, please leave a comment and share my facebook post or my blog post with your friends. It will not only make me feel good :-), but if I know at least someone has read it and benefited, I’ll be motivated to write the next lesson on Shutter Speed.
Disclaimer: I don’t claim to be a teacher of the english language or of the technology of photography, so please excuse any inaccuracies with either. I’m just going with what I know.