How Distance and Focal Lengths Affect a Photo

One of the most fascinating parts of photography is perspective. To get it right you need to know how distance and focal lengths affect a photo.

A common mistake I see when reading some crafts and design blogs is that people, out of ignorance, choose the wrong focal length for their photos.

Types of lenses (by focal length)

To keep it simple you need to understand that there are (simplification ahead!) 3 types of lenses according to their focal length:

1. Wide-angle (smaller numbers)
2. Normal (50 mm for film cameras).
3. Telephotos (bigger numbers).

Generally speaking, a normal lens roughly replicates how our eyes see things, a telephoto makes things look closer, and a wide-angle lens makes things look far away.

Here's a comparison:

How focal length affects pictures

On the first row you can see that if I take a photo of the same object. I am standing exactly on the same spot and changing the focal length (from wide angle to telephoto). At 200 mm we end up with an unnatural view equivalent to standing with our nose a couple of feet from the object. Of course, if we want to see the object up close, a telephoto is the right choice. But why not just get closer? See the row below.

The second row of pictures is the object, a box, as seen through different focal lengths, but I am trying to keep the object roughly the same size.  With each focal length I have to move farther or closer. A moderate telephoto (200 to 70 mm) gives the most natural and pleasing perspective. At 18 mm (a moderate wide angle) the image is very distorted.

Here's another example of how focal lengths affect perspective.

So, if you are going to get close and personal, better to step back and use a telephoto.

But if you are  not photographing an object, but an enclosed space, then things get more difficult. A moderate telephoto is best, but the problem is that we cannot get far away enough from the subject  to include large portions of the room in the picture.

You can do two things: You can either go out of the room, or as far away of that part of the room as possible to get as much in as you can (top left and right picture I did that, I am outside the room looking through a door), or use a wide angle lens and try to correct some of the distortion with a post-processing software (bottom left).

Or live with the distorted perspective, because some times it really doesn't matter.

When photographing people a moderate telephoto (starting at 50 mm for most common crop formats or 70mm for full format) produces the most pleasant result. Like for objects, wide angle lenses distort the perspective, and while it can be used for effect, generally people prefer to look good in pictures.

A wide angle lens make the part closer to the camera disproportionally large (usually the nose), that's how you get those photographs of people with very large heads and tiny feet. or an enormous hand pointing to the viewer.

Something like this:

This one was also taken with 18 mm, the effect can be made even more dramatic with smaller focal lengths.  But let's simplify this even more:

To simplify it

• If you have a fixed lens camera, well sorry, never mind. Carry on.
• If you have a point-and-shoot with a zoom lens, then try to zoom in as much as possible whenever taking a picture of an object, person or room, unless you know what you are doing and know what you'll get.
• If you have a DSLR, then knowing the focal lengths in the photos above will help you understand how your lenses work.

However be mindful that the bigger the focal lengths, the more light (or camera stability) you will need. So when using a telephoto you will either have to shoot with good light, or use a tripod (or support your camera in some way).

I hope I accomplished my goal of keeping these posts as simple, and the language as plain as possible.

If you want to learn some in-depth explanation on how focal lengths affect the perspective in your photos check these sites:
Using wide angle lenses
Using telephoto lenses

Focal lengths are calculated for an FX camera (crop), as they are more common.