This is a portrait photo by Annie Leibovitz. The person in the photo is actress Jodie Foster. Whoever took this photo used an extreme close up and also vignetting, so that attention is drawn to the face, and other details are dark.
This is another portrait by Annie Leibovitz. The subject of the photo is actress Angelina Jolie. Unlike the Previous image, this appears to have not been taken in the studio. This means there is no vignetting or studio lighting. Also, this is image is taken more from a mid shot perspective rather than as a close up.
The image above is taken by Alec Soth. This is a very different type of portrait than the other two above, as it is taken far further away from the subject; you can see the man's whole body. Also, this image was not taken of a celebrity. This was taken somewhere in public, and the background is a lot less neat than in the other picture; there is lots of uneven floor and there are bits of broken wood in the background.
This Portrait is much less detailed than the previous ones. It has been taken in a studio on a white background, with no vignetting or selective lighting. It has a wide depth of field, therefore everything is on focus. It looks almost like it could be a passport photo, partly due to the blank expression of the man feature in the image. This photograph was taken by Thomas Ruff