28 September 2011

More on Compression

To illustrate compression better, I've included the following pictures:




The one on the left is taken with the 85mm f/1.8.  The one on the right is taken with the 400mm f/5.6.  In this case, I tried pretty hard to keep them at the same size and fix the reference point (the brick column in the center of the background building).

The background in the second picture is much closer than it is in the first.  In a way this makes perfect sense.  What if we were going to focus on the background instead of the foreground?  It stands to reason that the background would "feel" closer with the longer focal length (greater zoom).

The important thing to realize is that when we keep the foreground elements the same size (roughly), the background will seem closer with a longer focal length.  In the first picture, I was perhaps six feet away from the subject.  In the second picture, it was closer to thirty or forty feet.  I would guess the background building is 500 feet or more away from the subject.

This, incidentally, is probably the way that we get some cool effects in Hollywood.  I'm thinking specifically of this shot from Lord of the Rings:


In particular, note in the beginning of the clip how the background changes compression.  What the filmmakers have done here is to rack the camera backward while zooming in.  A tree appears in the foreground while the background appears to get closer.  It creates just the sort of creepy experience you'd want when a Nazgul is about to appear.


No comments:

Post a Comment