# Dolly Zoom (Vertigo Shot)

Hi,

I am using TBS 4.5 to try to make a simple example of a dolly-zoom shot.

Problem: My foreground object shrinks and then grows larger again instead of staying the exact same size.

I have created an 8 field diameter circle centered on a 12 field Drawing and have the exposure extended to 48 frames. I have my Camera on a peg trucking in from the 12 Field to a 6 Field shot over the same 48 frames. I also have my Camera set on a dynamic zoom-out from an 18.4349 degree FOV to a 33.6901 FOV over the same 48 frames.

I did all of the math out using the formula:

Camera distance from object = (Width of Object) / (2 * tan(FOV in degrees))

I used Fields as my measure of distance and width, although I don’t think it should matter so long as I use consistent units.

Any help on why my foreground object doesn’t remain the same size throughout the 2 second animation is appreciated.

Sorry for the long-winded post. I tried to include all the details.

Thanks!

Okay,

Well to update this… I have fiddled around a bit more and am still stuck as to how to maintain the subject at a constant size during the dolly zoom. My test subject (the circle) seems to grow smaller over the first second or so and then grow larger again over the last second. I keep re-doing the math but its very messy.

Is there an easier way to achieve the dolly zoom?

Hi,

You shouldn’t change the FOV if you want to do a simply Dolly-Zoom shot. The FOV change is most likely what that is making your elements change of ratio back and forth.

For a truck and zoom of the camera you should simply attach that camera to a peg and afterward move/scale that peg according to the movement that should have been done.

Regards,

Ugo

Hi,

I don’t think I am following you. If I don’t do a dynamic zoom of the camera (change the FOV), how am I going to achieve the zoom part of the effect?

If I attach the camera to a peg and do my truck-in movement by making a motion path for the peg, I still need to zoom out at the same time to keep my object the same size while expanding the field of view and exposing more of the background.

Thanks

Hi,

You can use the top or side view to move your camera closer to your elements. Toon Boom Studio as a 3D environment in which you can move your element with peg so this allow you to do advanced scene planning as well and camera move and zoom.

Regards,

Ugo

Thanks,

Well, it looks like I was making this more complicated than it is. I was looking at it from the live-action method of moving the camera in while zooming out. But of course, in animation, unlike real life, I could simply put the background on a peg and move it backwards while keeping the foreground in place. This achieved the same effect of “stretching space” between the character and the background.