How to adjust the aperture of Canon 450 to the maximum aperture?

The f/3.5-5.6 written on the lens shows that this lens is not a constant aperture lens. The maximum aperture that the lens can reach is 3.5 at 18 mm and 5.6 at 55 mm

If you want to manually adjust the aperture, you can use AV or M gear, rotate the lens to 18 mm (you can see the scale on the lens), rotate the wheel next to the shutter in AV mode, you can adjust the aperture to 3.5, and then rotate the lens to zoom. You can find that the aperture displayed on the LCD behind the camera will automatically change slowly from 3.5 until the lens zooms to 55 mm, and the aperture number will become 5.6. During this period, the reading will be made.