Camera movement confusion

[Jkoseattle]

I have a figure that is fairly far away and positioned in the left third of the screen. I want to very quickly zoom in on this character's face, in about one second. I created camera track and camera zoom keyframes for this, but the zooming doesn't appear "straight". As I simultaneously zoom in and track them from the left third to the center of the screen, the character appears to move further to the left and then quickly moves to its correct stopping place in the center rather than looking like a straight zoom in. At first I thought this was some sort of interpolation effect, but I changed both tracking and zoom to Linear interpolation and the effect remains. So now I'm thinking it's some sort of expected illusion that people who really know the optics of this would understand and know how to account for. Is this making sense?

If not, here is a more detailed description. At frame 1 of the zoom/track sequence, the character's face is at about 30% left. At the end it is right in the middle, or what I'm calling 50% left (I'm sure there is correct jargon for this, stay with me). Halfway through the zoom I would expect the face to be 40% left, but in reality it's almost all the way off the left side, like 10%, quickly centering itself at the end of the sequence to end up in the right place. How come?

[obtusity]

I suspect it's more a case of simple mathematics concerning field of view - in real 3D life you might compensate by rotating the camera somewhat rather than tracking.

Your camera has to zoom more than it has to track, so half-way it has zoomed, say, 300% but only tracked a little to the left.
Consider if you zoom that same amount straight ahead without any tracking or rotation, the character will appear to be travelling quickly towards the camera-person's left side and may go off-screen very quickly as it disappears from the field of view.

You might want to add another intermediate tracking keyframe (without changing the zoom) so the camera tracks more quickly to the left at the beginning, so the last half of the zooming is more straight on, but slower tracking.

[slowtiger]

If you don' need any Z information, instead of moving the camera just put all artwork into one group layer and scale/move this. It helpf when you put this layer's origin exactly at your character (or whatever has to be in center).

[hayasidist]

... but if you want to use camera, you can put that extra key in as suggested by obtusity (but be aware that if you use the default "smooth" you'll ease in and out of that point) or you can use Bezier interpolation to change the exact path

[Jkoseattle]

Thanks for all the advice! It's like Christmas every day. I go to bed having just posted a question, and in the morning the answers magically appear under the tree...

Translating the objects instead of the camera was a good idea. But it causes too many other unintended issues with my scene elsewhere, so that was out. Eventually the best solution was to massage the camera movement in the motion graph. Which was good anyway because I hadn't done any motion graph surgery to that point, so now I know how to do that.

Anyway, problem solved, thanks again!