Focal Length: 55 mm

Focal Length: 85 mm

Focal Length: 125 mm

Focal Length: 200 mm

Right now I’m not concerned with the how or the why, only the end result.

I used to think the millimeter numbering on cameras and lenses (the focal length) would be one of the most confusing parts to learn. (Can I get it in inches?) Actually, it turns out, it’s a lot simpler than I ever could have imagined. One can learn about it in various depths, but as far as I as a relative beginner learning the terms need to know, “mm = zoom”.

The lower the focal length’s mm value, the less “zoomed in” a lens is. If you’re on a safari in Africa with an 18 mm lens, and you see a far off pride of lions, you have to choices: 1) settle for a photo with the lions so small that you can’t tell they’re lions on the photo, or 2) get close enough to the lions that you’ll likely be their dinner, but boy what a nice photo you were able to get!

The higher the focal length’s mm value, the more “zoomed in” a lens is. Same safari, but now you have a 300 mm lens. Now you can remain far enough that the lions don’t see you (or care to bother with something so far away), but your camera lens puts your view so close to the pride that you can tell what Simba had for lunch by looking at his teeth in the photograph.

That’s quite the exaggeration, but it gets the general idea through. The higher the number, the further objects come close. But what good is it just to read that? How about seeing some photos taken at different focal length?

First, though, I need to mention this: 18mm with one lens will not provide the same area in a photograph as 18mm with every other lens. Therefore, the area photographed in the results below may only be true for the lenses used to take them. This is because the millimeters refers to the design of the lens, not the area the lens photographs.

First, photographs taken with my HP PhotoSmart 735.

This is taken with a focal length of 6 mm.

Now we’re up to a focal length of 17 mm.

Those are the high and low extremes of my point-and-shoot camera.

See? The higher the number, the more zoomed in on the subject.

How about using a Nikon D40 with a 18–135mm lens?

You might expect that 18 mm might look close to the 17 mm above, but the point-and-shoot camera’s lens and the Nikon’s lens aren’t a 1:1 match for focal length distances. Compare the second image above (17 mm) with the one below (18 mm):

This is 18 mm with my Nikon D40’s lens. It looks closer to the HP Photosmart’s 6 mm! This just goes to underscore that 18 mm for two camera will not produce the same area in a photograph.

However, I’m more interested in showing how a higher focal length is directly associated with “zooming in”. Let’s continue.

Here we’ve moved up to 58 mm.

And now we’re up to 135 mm.

Can you imagine how close 200 mm would be? Or 300 mm?