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Now we're going to look at how to visually resize a composition's pixel
dimensions. Not its duration, its actual area. Now what we have here is an old
public domain clip. This from the Star Is Born, a classic wonderful movie from
1937. This is encased in a composition that is standard NTSC size.
In other words, 720 X 480. If we look at the comp in the Project panel,
it's significantly smaller, 336 X 256. Now let's say we're putting this composition
on the web. I don't want all of this extra black space around my clip. I just
want to crop it to this clip. A quick and easy way to do this is by clicking
the Region of interest button down at the bottom of the Composition panel. Click
that to select it, and then click and drag almost like a marquee around the
footage. Now the purpose of the Region of interest
is to make it so that when you render your footage or render your composition, it
renders only a small piece of it. So let's say I had many layers around this
other layer here and maybe there were sparks and a whole bunch of stuff going
on around it. I only wanted to preview what's in here. Now that's going to
speed up my render time a lot because now After Effects won't have to render
this stuff on the outside of the region of interest.
But an added benefit of the region is that once we have a region of interest
and it's active, by the way you can deactivate it by clicking the Region of
interest button again, once it's active, you can go to the Composition panel
and select Crop Comp to Region of Interest. And now our composition is exactly
the size that we chose. So essentially this trick is a way that we
can visually resize the pixel dimensions of a composition. Now I do realize
that we could have gone into our Composition Settings, and just made a composition
that was 336 X 256. Likewise we could have just dragged the footage to
the New Composition icon at the bottom of the Project panel.
However if I undo this by hitting Command+Z on the Mac and Ctrl+Z on the PC,
what if we had this clip over here on the left hand side, perhaps in the corner
like this. Then cropping the composition to the Composition Settings would not work.
Or let's say we made a large composition with a lot of layers and we only
wanted a small piece of that to be exported somewhere. So again this trick is a
really great tool to export a piece of a composition for export.