Aperture - Taking Better Pictures Tutorial 1a

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Aperture - Taking Better Pictures Tutorial 1a

Post by travis_cooper on Mon Feb 25, 2008 4:10 pm

The first element of exposure I'm going to cover is your aperture. The aperture works a lot like the pupil in your eye. When it needs to let it more light, in a dark room for example, your pupil opens up really big. When you are outside and the sun is shining really bright your pupil will shrink down really small to let in less of that light. Your camera's aperture works the exact same way. If you need to let in more light you open up your aperture, if you need to let in less light you close your aperture.

Another important thing your aperture controls is the dof, depth of field. This is basically the amount of the picture that is in focus. A small dof would have just the area that you focused on in focus. A large dof would have the entire picture in focus. With your aperture open all the way up we get a smaller dof, with your aperture closed all the way we get a larger dof. Here is a list of some full stop values for your aperture. Some cameras, especially point and shoots, won't have quite all these numbers. Also remember these are full stop values, your camera may show half stops, or possibly third stops, in between these numbers. Also the numbers are really fractions, so even though f/2 is referred to as a low f-stop, it is actually a bigger number than f/32, which is why it is a wider open aperture. This can be confusing at first, you just need to play with it until it sticks in your brain.

f/2 Wide open aperture - smallest dof
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22
f/32 Closed down aperture - largest dof

So at an f/2 our aperture, the pupil of our camera, is opened up as far as it can so we are letting in the most amount of light. We are also creating a very small dof, so if you take a picture of a person's face and focus on their eyes, not much outside of the eyes will be in focus, the rest will be blurry. At f/32 our aperture is closed down to a really small circle so we aren't letting in very much light. We are also creating a large dof with this, so if we take a picture of that same face we see pretty much everything is in focus.

Here is an example of a low f-stop. This shot was taken at f/2. Notice the small dof, only the branches of the tree are in focus, while the building in the background are out of focus.


Now in contrast here is the same shot, but now we have a larger f-stop. This shot was taken at f/11. Notice that now the branch and the building are both in focus.


So controlling your aperture can give you a nice affect by blurring out the background, or other objects as you need it. But how do you set your aperture? Well this will be our first experience out of those auto settings in our camera. Set your camera dial to Av mode, some may just be A, this stands for aperture value and is called the aperture priority mode. The nice thing about this mode is that you get to set the aperture to what you want and your camera will set the shutter speed for you to get the appropriate exposure. It will also use the ISO that you have set, usually the ISO has to be set in the menus of your camera somehow, you will need to read your manual to figure this out when we talk about ISO later. Now your camera probably has a little wheel, if not you probably use your arrow keys, that you can spin to set the different aperture values. As you change different aperture values your shutter speed should change as well to keep the proper exposure. If you ever choose an f-stop that gives you too much or too little light for your shutter speed to accommodate it will let you know by blinking. So for example if you are outside and it is really bright and you set your f-stop to f/1.4, which lets in a lot of light, and your camera's fastest shutter speed is 1/4000 and that just isn't fast enough, it will set it to 1/4000 and that number will be blinking letting you know that it is as fast as it can go, but it isn't fast enough to get the proper exposure. It will still let you take the picture, and everything will be really bright, some parts even totally white, but your camera tried to warn you.

Play around in Av mode. Take pictures of the same object at different f-stops and see what the difference in dof is. If you have any questions regarding aperture please ask them here. If you have photos that you want me, or others, to look at and help you with just post them and ask, we will be happy to help.

Go to the next tutorial - Shutter Speed
Exposure
List of Tutorials

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