Taking pictures with Canon 450D SLR camera, the color background is blurred and the foreground subject is very clear. Excuse me, how to adjust the camera exactly

Let's see what lens is used first. There are three methods to blur the background: large aperture, controlling the background distance and telephoto magnification.

If the large aperture lens of 50 1.8 is relatively simple, and the AV aperture takes precedence, and the aperture is adjusted to be between F 1.8-2.8, the large aperture will naturally have a shallow depth of field, which is what you call background blur.

If the ferrule 18-55 3.5-5.6 is used, the background blur effect is not as good as that of a large aperture lens. You can also use AV aperture first, and the aperture is F4.5-5, which is the aperture with better imaging quality of 18-55 lens. The camera is close to the subject, and the subject must be far from the background. Only in this way can we achieve the effect of blurring. The situation is not as well controlled as a large aperture lens, otherwise a good large aperture will not be so expensive.

Finally, use the telephoto lens to zoom the subject directly, and the background will naturally blur. However, 18-55 is not a telephoto, and the effect may not be ideal.