Zoom out followed by freeze causes illusion of zoom in?

deisenberg wrote on 10/9/2003, 8:55 PM
Another question from a newbie. . .

I'm constructing a photo slideshow. (Just had a baby girl; our first!) I'm using the Pan/Crop tool to "zoom" in and out on the photos. At the end of each photo, I freeze on the last position for a few seconds, before crossfading into the next photo.

What I'm observing: after a zoom-out effect of several seconds, when I freeze on the final image, it appears to my eye that the image is zooming in slightly. I assume that this must be an optical illusion, since I'm sure I haven't done anything to deliberately cause this effect.

Does this make sense to anyone? Do I need to see my ophthalmologist, or is this an expected visual side effect? What might I do to mitigate the problem?

Thanks so much,

David

Comments

GerryLeacock wrote on 10/12/2003, 12:51 PM
I'm curious, how are you making it "freeze" on the last position for a few second. I thought it went seemlessly from the [start] to the [end] with out resting anywhere. It could be that it's starting to loop to the start again, as it's been stretched out.
Chienworks wrote on 10/12/2003, 1:37 PM
I would say that this is a normal visual effect. After seeing a constant phenomenon stop, your brain tries to assume it is still happening. Since your brain thinks the image should still be getting smaller but it is in fact remaining the same, it appears to be doing the opposite, or in this case getting bigger again.

It's easy to demonstrate this "opposite" effect in lots of ways. Sit in your swivel chair and rotate rapidly in one direction, then bring youself to a sudden stop (you may need to have a bucket handy!). The room will look like it's still spinning the other way. Stare at a phonograph record spinning for a while. Stop it suddenly. Now it seems to be rotating the other direction.

Brains are strange things sometimes.
deisenberg wrote on 10/12/2003, 10:04 PM
Gerry,

The "freeze" is created by adding a duplicate of the original photo after the one in which the "zoom" takes place. The duplicate is positioned precisely where the previous zoom ends. (The procedure is described on pages 90/91 of the newest version of the user manual.)

David
deisenberg wrote on 10/12/2003, 10:06 PM
>Brains are strange things sometimes.<

At least mine is, apparently!

Thanks for the clarification. I'll keep playing with this and see if there's anything I can do to minimize the effect.

David