This is really easy. Remember on the last page we said lenses have variable apertures, and that the size of those apertures affects the depth of field?

Well, here are three pictures of the same lens. It happens to be a lens from one of my film cameras, but it could be just about any lens.

The lens on the right is at Aperture f1.8 (its widest aperture). This lens lets through more light than either lens below.

This lens is set to Aperture f16; it lets through less light than either lens above.

Now, that wasn't hard, was it? The reason I'm showing this is that digital cameras often have lenses which are physically very small compared to some film-camera lenses, and seeing the action of the aperture can be very difficult.

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