My aperture was set at 2.8 for this photo. The focus was on my son's right eye. You can see everything softening up and blurring in the photo. (The busted lip was due to him hitting himself in the face with a Nerf Gun).
2.8 aperture on this photo as well. The focus is on the fly on my dog's nose. The rest of the image is blurred.
I wanted this photo to be sharp, so I set my aperture at 7.1.
AV for Canon or A on a Nikon: That is your aperture value. You set how wide you want your lens to open up, and the camera does the shutter speed for you. If you had time to purchase a prime lens, you can play around with this feature. The lower the Aperture Number on your settings...1.8. 2.8, etc. the wider your lens opens. Your camera will take a photo with the focus point very sharp (crisp, clear). The rest of the photo will soften up, making it less in focus or more blurry. The smaller your lens opens up 5.6 or higher, the more sharp and crisp your whole photo will be.
You must remember that your aperture value in AV Mode will set your shutter speed. The more light you let in, the faster your shutter will go (open and close). The smaller your aperture, the slower your shutter will go. So if you are inside, and it's sort of dark, you will want to widen your aperture. (Lower the number on the dial) It will allow your shutter speed to increase. You will have softer photos, though the wider you go.
Your shutter speed is important, because the slower your shutter opens and closes, it will show blur if there is movement.
I hope this makes sense. Let me know if you have questions (leave them in comments). Next week, I will talk about the TV or time value mode.