For changing the shutter speed, put the mode dial on Tv (as in the image below: make sure the white line corresponds to the letters Tv ), and turn the wheel high-lighted in red below (excuse my crappy images, I edited all this as something quick and dirty).

On your LCD screen, you can see the below screen (let me know if you don't know how to get to this screen). The 1/200 is in seconds - you can go anywhere between 1/4000th of a second to 30 seconds. When you turn the wheel, the number changes, which indicates the change in shutter speed. Make sure you have enough lighting when you choose a very fast shutter speed.

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Similarly, for changing the aperture, put the mode dial on Av (as in the image below: make sure the white line corresponds to the letters Av ), and turn the wheel high-lighted in red below.

On your LCD screen, you can see the below screen. The number you see here is actually the denominator (F2.8 actually means f/2.8) For Aperture, the minimum and maximum varies with the lens you have attached. I have a Sigma 18-50 f/2.8-4.5 lens attached on my camera, so you'll see that my aperture is f/2.8.

There is more to the F numbers, but since I don't want to confuse you with all the jargon, I will keep the things simple.

A smaller f number is also called a wide aperture, and a larger f-number is also called a narrow aperture.

The smaller f number like an F.1.8 or F/2.8 is useful when -

• If you are shooting in low light - the lower F number allows lots of light to enter into the picture, so that will be useful (that is why it's called wide aperture).
• If you want a very shallow depth of field (e.g.: foreground in focus, but background blurry - imagine you are taking a picture of a flower, and you want only the flower in focus, and the leaves in background to be out-of-focus).

Choose a higher F number like F8 or F11 -

• If you want small amount of light to enter (that is why it's called narrow aperture) - for now I would say don't worry about this, you can learn more once you become more familiar with photography.
• If you want a deep depth of field (e.g.: everything in focus - think of a scenario where you are taking a picture of your friends with a far-way mountain, and you want your friends and also the mountain sharp).

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Finally, one thing to keep in mind is the aperture and shutter speed change in effect to one-another. For simplicity (and skipping the jargon), when you select a fast shutter speed, the aperture will change to a higher f-number, and when you select a slow shutter speed, the aperture will change to a smaller f-number.

Similarly, if you select a small f-number (wide aperture), the shutter duration will increase (slower speed), and selecting a high f-number (narrow aperture) will decrease the shutter duration (faster speed).