blowing backgrounds out

Steve Laramie

Steve Laramie

Veteran
I see this done in alot of films and iv done it myself a couple of times by accident. I was wondering how you blow the background up.( having the forground stay the same but it seems like the background is geting bigger and closer). I know it has to do somethign with pulling the focus and zooming. Im shooting on an xl2 and a dvx by the way.
 
It's all about changing your focal length. When you go from a wide to a long angle, in order to keep the foreground the same size, you'll have to dolly out.
 
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Anytime you zoom in on a subject it compresses the space between the subject and the background. So, the longer the lens the closer your background will be.
 
I'm not sure if I get you correct but by zooming in an object at the same time as you are making a camera movement, e.g. with a dolly, backwards you get the background wider but still keeps the object the same size. A really nice effect if you get it right.

David
 
Its called a contra-dolly zoom shot. It takes advantege of the difference in perspective shifts between a zoom and a dolly. A zoom alters the size of the every object in the frame, thus zooming in causes objects in the background to grow larger at the same percentage as objects in the foreground. A dolly however has a larger effect on objects in the foreground than those in the background. Dollying in on a scene, the objects in the foreground will get much larger, while objects in back will be affected much much less, depending on how far away they are. Thus if you zoom in on a subject the whole frame, including your background gets much bigger. However if you dolly out as you do so, the objects close to frame will get smaller, effecively causing them to remain the same size, while the objects in the background, since they are not as affected by the dolly, will continue to get much larger.
Its a tricky shot to pull off well, but when done correctly and at the right time can be very nice.

Good Luck
 
contra dolly push and pull ying and yang... yup... dolly back while you zoom in... or is it the other way around?? Haven't done it in a while... YUP... it's dolly backwards.... zoom in... then THRILLER!!
 
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you can also dolly in while you zoom out, gives the opposite effect. i think woody allen did that one a lot, while the first one was more hitchcock. might have it backwards, tho
 
Yes mrWr0ng you can, its still the same principle described above, just the background will fall away, uncompressing the space essentially.
 
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