What does the focal length of a camera lens have to do with the results of a closeup portrait photo? Somebody said that it makes a big difference, but if you’re zooming in with the same composition of the face in the photo, what difference will the focal length have on a human face? Or on a still life, for that matter?
With a short focal length lens, the nose appears relatively larger, and the ears look relatively further away – enough to make a difference to the appearance of faces. That’s because to get the same size fiace, the camera has to be closer with a short focal length lens, and so perpective is exaggerated.
2 reasons- First, a longer focal length (80-120mm lens) will generally have a smaller depth of field than a shorter focal length (~35mm lens). The shorter DOF results in a very blurred background which is desirable for potraits, as it makes the subject stand out.
Second, a shorter lens generally tends to elongate a persons features, resulting in a bit of an unnatural look (conversely a very long lens would compress features). Most people seem to think that 80-120mm results in the most “natural” looking results.
For an extreme example of this; check out the photography at http://www.thedog-clubs.com/home.html
One thing you will notice is that if you use a wide-angle lens and have a person’s hands or feet in front of them, they will appear distorted – either slightly or greatly elongated depending on your distance from the subject and the width of the lens. At the extreme end is the fisheye lens which gives a funhouse mirror effect.
The depth of field issue is also very important – you want enough depth of field so that your subject is in focus but any distracting background objects are blurred. If you have any highlights in the background, a shallow depth of focus will give you what they call “bokeh” which, depending on your lens, most people find to be an attractive effect.
Most people seem to think that 90-120mm is about the right range for a portrait lens although it obviously depends on the format you’re shooting. Non-SLR digital cameras tend to be difficult to get shallow depth of field because of the small size of their sensors.
To say that a wide angle lens will distort faces, elongate nose etc. is a little misleading. The effect is caused by the viewpoint rather than the lens itself. What happens is that, using a wider angle lens, the photographer has to get in much closer to fill the frame. When printed the pic looks distorted because the wide field of view fools the brain into wrongly interpreting the taking distance and the so perspective looks exagerated. You can prove to yourself that this is so by using a w/a lens but from the distance you would use with a longer focal length, leaving lots of space around the subject. You can then enlarge just the central portion and you will see the perspective is just as you would expect from the longer lens.
Bingo. I was about to reply and say the same thing myself.
Just about any decent photography book has examples of portraits taken with a variety of lens lengths, but I had a surprisingly hard time finding the equivalent demonstration on the web. This page includes a pair of pictures of a car, taken to illustrate the difference between wide-angle and normal lenses. (Scroll down to the “Wide Angle Lenses” section.)
Good reply ticker, I’m always amazed at how many photographers don’t know that.
On a related note depth of field is similarly indirectly related to focal length. The calculation is somewhat complex but the big factor aside from relative aperture is magnification ratio. If I take a portrait with a 35mm film camera, once with a nice 85mm lens at f4.0 and again with a wide angle 24mm lens at f4.0 but closer so I still have the same area of view I’ll have the same depth of field in both cases. Perspective will be dramatically different only because I’m at a different distance in each case.
Magnification ratio becomes an issue with consumer digital cameras. Because they have a tiny sensor chip the magnification ratio is so low that it becomes nearly impossible to get an intentionally reduced depth of focus which is often desireable. You can fake it in photoshop but an artifically blurred background doesnt’ look like an optical bokeh. The opposite is true of large format cameras (4"x5" film or larger) where a typical portrait will have such a high magnificaition ratio that even with tiny apertures the available depth of focus is razor thin.