Normal has the focal length equal to the diagonal size of paper/film. With the 5 by 7 inch paper most of us are using, we need to build a box with roughly 9 inches (23cm) focal length to achieve a normal perspective. Normal lens/pinhole creates very similar perspective to that of human eye.
Wide Angle has shorter focal length than normal. It has a wider angle of view. Visually, wide angle exaggerates the perspective, "pulling" the closer object closer and bigger, and "pushing" the background further awaya and smaller. You can use wide angle to create interesting leading lines and other dynamic visual effects. All cameras built with IKEA wooden box in our class are wide angle. If you heard of something called fisheye, it is basically an ultra wide angle with extremely distorted perspective that curves the straight lines.
Telephoto magnifies the objec and compresses the perspective. Visually, it pulls the foreground and background togeter, as Professor Serafino has demonstrated with our lined-up group portrait, where the distance between the first and last person in the line seems shorter than it should be. Building a telephoto pinhole camera gives you less distortion in perspective, which is generally the desirable effect in portraiture.
Ji
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