This is for the Orange challenge on the photography board here:
The goal of the challenge was to photograph something orange while playing with different focus points. Well, I changed apertures and focused on the same thing - the eye. I also adjusted my shutter speed to get an equivalent exposure each time.

The wider my shutter was opening (smaller the number - 1.8), the faster my shutter needed to be to let in the appropriate amount of light. The smaller opening (larger number - f10 and f16), the slower my shutter had to be to allow more light to come in the smaller opening.

You can also note that the depth of field changed dramatically with the various apertures. With the wide open 1.8, the DOF is very shallow and you have to be careful of your focus point or your subject will be blurry. You have to be careful at this aperture (fstop) also because it's easy to get one eye in and one eye out of focus if your subject is turned slightly away from you and the eyes aren't in the same plane. This is good or bad depending on the effect you want. With the smaller aperture (f10 and f16), I got a deeper DOF. In other words, my background was in better focus. So when you have a group shot or a landscape, you may want to set your aperture to open less (bigger number) to get everyone/thing in focus.

Photos taken with my Nikon D70. I forgot that my ISO was set to 1600 which created quite a bit of grain.