Will Gunadi Photography

Recently a good friend of mine who had just taken up photography asked me a good question:

“Why does a long lens (= telephoto) produces pictures that has nicely blurred background, even more so than an expensive, fast (= big max. aperture) shorter lenses?”

Well, it’s been my intention to explain this to those who took my workshop also, so why not kill two birds with one RB67 (… sorry, baaad photog joke).

So I answered his question thusly:

Longer focal length gives you the illusion of shallow DoF (nice blur) because of its magnification factor.  Similar in principal to macro-photography, but that’s another separate topic.

Consider this picture:

Taken with a 600mm lens.  The bird is actually far away, it should be very small, but due to the 600mm lens’ extreme magnification, it is sizable in the frame.

But guess what, not only the bird is magnified, the background is also. It is rendered without any details, not because of the depth-of-field, but because it has become proportionally bigger (remember, a little blur looks like a total blur when magnified).

Now, of course we should take advantage of this.  Wedding and wildlife photographers have relied on this effect a lot to produce their awesome photos.

But like anything else, you can’t use it for every situation.  Sometimes, you do want to include some background and still have the blur, you can’t do that with long lenses.  You can only do that with high quality and fast wide angle lens.

Just Add Perspective

Another reason to keep both wide and long focal length is: perspective.

- Wide angle (short) lenses exaggerate perspective, buildings will converge into the horizon, trees and other tall or long objects will become distorted.  Like this:

See the power line? distorted.  This was using 20mm lens. Super-wide.

- Tele (long) lenses compresses perspective, stuff that is far away looks the same size as the one in front of it.  Like this:

See the far away wind-mill looks almost the same size as the front one.  In reality, those are hundreds of meters apart.  This was taken using 400mm lens.

In summary, sometimes you want exaggerated perspective (or just include a lot of things in the frame), sometimes you want to isolate subjects (easier to do with longer lenses).

So, even though your wallet may not agree, you neeed both types of lenses.  :)