There's 3 key parts for an exposure, you have your aperture, shutter speed and ISO.
I'm going to cover apertures in this part.
So, what is aperture?
Well simply put an aperture is an opening that light travels through.
You can change the size of the aperture (The size of the opening) to let more or less light in.
A smaller aperture (Larger number) lets less light in than a larger aperture (Smaller number).
Here's a visual representation to help you if you're confused.
Now why is this important.
Well first of all, aperture effects the light coming into the lens so obviously this will either make an image darker, or brighter.
But it also deals with something else, something called Depth of Field.
What's depth of field? Well, if you don't know what it is, I'm certain you've come across it at one time or another.
Basically the depth of field is the portion of a image that appears sharp (In focus) in the image.
An example of this would be like this image..
What's the difference, obviously the bottom image has just a narrow area that's in focus, the rest is blurry.
So how can you control this? By changing your aperture.
If you have a larger aperture (Smaller number) you will get a shallower depth of field (Like the bottom image in the last pic). If you have a smaller aperture (Larger number) you will have more in focus.
Now what does all this matter besides how it make the image look? It can effect your shutter speed. Here's an example.. If you're taking a photo at 1.8 at a 200th of a second to get an average exposure. Now if I change my aperture to something like 5.6 I'm going to have to change my shutter speed to something like a 40th of a second. Because since you're making that aperture smaller (Larger number) you're letting in less light. So to make up for that and get an average exposure you have to slow down your shutter speed.
And visa versa, if you have a smaller aperture and you open it up, you have to increase your shutter speed.
Your apertures are completely dependent on what your lens is able to do.
Some lenses can go up to f45, some can only go down to f2, f2.8, f4, f5.6
Have you ever wondered why a lens of the same focal length, lets say a 70 - 200 f2.8 lens costs $1,999.00 but a 70 - 200 f4 lens costs $970.00?
Well because as I've told you, a 2.8 lens gives you a larger aperture, which is great especially if you're shooting in low light conditions, like a concert, at bars/clubs, churches, whatever, it gives you a shallower depth of field which is great for portraits.
Also have you ever wondered why a lens might say, "75 - 300 f4 - 5.6"
What that means is as you're zooming the lens from 75mm, to 300mm the f stop (Aperture) goes from f4, to f5.6. So if you're at 300mm, you can only shoot as fast as 5.6, you can't shoot at f4. But if you're at 75mm, you can shoot at f4.
So that's why you're paying extra.
It might sound like you're paying a lot and not getting a lot out of it, but you are. If you're doing any sort of professional photography you need fast lenses (like 2.8, 1.8, 1.2, etc) because you can't afford to take a photo at a slow shutter speed and have a blurry image (At least, for most clients... Unless it's something you're trying to go).
And here's an example, if I were to shoot a photo right now from my room at 5.6, I'd get a blurry picture. Because it's kind of dark so my shutter speed was around a 6th of a second. Now just changing my aperture to 1.8 let me shoot at a faster shutter speed so I was able to get a non blurry image because I was shooting at a 60th of a second.
I hope that helps and that you've learned something.
If you have any questions, comments, concerns.. Hate mail, whatever. Feel free to message me or post here. (:
I'll continue with Shutter Speed next, then ISO.
