a little lesson

A girlfriend of mine recently asked me for a crash course in ISO, Shutter Speed and Aperture. She is always playing around with editing her digital images for Facebook (they are turning out great, btw!) but she wants to start using her film SLR more often. What started out as a short email listing a few tips turned out a bit more wordy than I planned (sorry about that, Laura!), but I thought since I had it written out already, that I might as well post it in case anyone else had an interest and could benefit from it! Here we go...

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The three things you'll need to learn to control if you want to get off of Auto Mode and into Manual Mode are ISO, Shutter Speed and Aperture (also called F-Stop).
The purpose of the above three tools is to capture light. That's what photography is all about, light...how to get it, how to use it, and how much you need to correctly expose your photograph. So these are the three tools you'll need to get that light...
Okay, so let's start with ISO:
The ISO number is the speed of your film. The measure of the film's sensitivity to light. The higher the number = the faster the film, which means that you can take photos in lower light situations. The downside to a high ISO (eg. 400, 800, 1000) is that the photos may come out more grainy, which is sometimes cool if you want that effect (on black and white photos for example) but not always desirable. The way to think about it is, the more light you are going to have (a bright sunny day) the lower the number needs to be. Keep in mind...ISO is not the only thing you can use to capture that light, so if you have a low ISO but not much light, you need to move onto the next two ways to get it...

Next is Shutter Speed:
Both the Shutter Speed and the Aperture (F-Stop) deal with the camera's shutter, which is released when you press your shutter release button on your camera (the button that takes the photo). Shutter speed is the length of time the shutter of a camera remains open before it shuts. The longer it is open (or the slower your shutter speed is), the more light it lets in and the brighter your photo. The numbers work something like this...1/250 of a second, 1/500 of a second, 1/1000 of a second, etc., getting faster and faster. The advantage of a really fast shutter speed is that your photos (as long as they're focused) will probably be sharper because it is not likely that your subject will move faster than your shutter. Lower shutter speeds (1/30, 1/40) are dicier, because you may shake the camera while your taking the photo, or your subject might move and the photo will come out blurry. As a rule your shutter speed should not be slower than the length of your lens. For example, if you are using a 50mm lens then don't go slower than a 1/50 shutter speed. If that is still not slow enough to get enough light for your photo, then you'll have to use Aperture (F-Stop) to compensate...

Aperture:
Aperture or F-Stop refers to the size of your shutter opening. The larger the opening the more light it lets in and the brighter your photo. The numbers are a bit confusing, because they seem to work backwards. The smaller the number, the bigger your opening. The bigger the number, the smaller the opening. (eg. F5.6, F8, F11). The other thing that F-Stop controls is the area of focus. So if you have a small number (like F2.8) and the opening is larger that means that your focus has to be more precise. If you focus on the eyes of your subject, the background and foreground may be more out of focus. Things in your photo will get blurrier the farther away from your focus point they are, so you have to make sure that you are focusing on just what you want in focus to get the effect you want. Its a cool effect though, to have the surroundings out of focus and your subject clear. Alternatively, if you use a larger number for your F-Stop (eg. F22), which means your opening is small, you will get more focus area. So for larger groups, landscapes, or anything else where you'll want more stuff/people in focus, use a larger F#.

In order to use all these tools to get the right exposure for your pic, I use my in-camera light meter. When I focus on a subject and look in my view finder I can see a scale at the bottom which is my in-camera meter. It will tell me if I am over or under exposed and then I will adjust these numbers to get the effect I want, as well as the right exposure.

Phew...I think that's it for now. Hopefully this was as useful as it was long! ;)

Thanks everyone!