A very brief lecture on zooming

I don't want to be a smartass, but there are probably people out there interested in this stuff who don't know it by now. Plus I really do love the effect. Actually it is one of my favourite effects in movies. Otherwise I didn't want to show the pictures because they are either too similar (same object depicted) or too different (by way of which object is in the focus).

Below you do have two pictures of approximately the same scenery with one main item depicted roughly the same size in both of them while others seem to change size.

Here we have a picture with with camera in position 1. A "normal zoom" with a ring in the foreground and la defense in the background. Please recognize the relative sizes.
In this picture you see the ring still having roughly the same size, while la defense grew considerably and now looks much closer.

This effect was done by zooming in, while moving backward with the camera. As shown in the illustration below.

This image shows the setup of the two pictures above. You see the camera positions for the two pictures above, la defense illustrated by the smal bird-object and the ring by a simple line.

The effect is clearly shown if one compares the "size" of the picture plane at the background object. By zooming to position 2 the plane became much smaller at this point by reducing the angle. This is very much what you want you zoom to do, because it increases the size of your objects relative to the picture.

By moving the camera backwards the size of the picture plane at the ring was kept at the same size.

If the two pictures would really have been made for a series, I should probably have watched the focal point more closely and should have kept the size of the ring more precisely. But as I was just looking for a more beautiful shot through the ring I am satisfied here and simply kept the better one.

If you look very closely you will recognize a second effect of zooming, which is reducing the depth of objects. Take a glimpse at the "depth" of the ring in both images. Although this effect was wanted for the area between la defense and the ring it probably is not wanted for the ring itself. The lection of this probably is, that one should never underestimate the effect of the zoom.

I for myself normally try to move myself if I wish to get closer to my objects because of this. But if you know what to do then you might achieve some nice effects. As, I think, the one shown above.

2 comments so far...

Gergana Vasileva December 02, 2006, 11:34 AM
Thanks a lot, for this lecture, Lars!!! You’ve explained this interesting effect very detailed and it was really useful for me! Till now, I didn’t notice that it’s not just a matter of zooming in, but also we need to move the camera backwards! If I knew that before, I could keep mine Quercus nut (in the front plane) at the same size in both pictures:
http://www.23hq.com/gergana/photo/1189682 and the next one:) Will try next time!!:o)

Concerning two pictures with the ring... I like them both!;) , but maybe the first one is better – has more space, more air! The anterior black iron of the second shot gives that line, which somehow holds the eye, framing the view.

my January 03, 2007, 04:36 PM
cool explanation and illustration, thanks!
gotta try this...
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