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How to do focus?

Posted: Thu, 27th Nov 2008, 9:02pm

Post 1 of 5

Lerman Productions

Force: 410 | Joined: 14th Jul 2008 | Posts: 72

CompositeLab Pro User

Gold Member

In most movies, there is a blur around a person. This is focus. I know how to do focus, but it seems way too hard to trace something every time I need to focus it. How do the professionals do it and how can I do it with Composite Lab?
Posted: Thu, 27th Nov 2008, 9:14pm

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

What you are thinking of as focus is actually Depth of Field. It is a result of the lens that is selected and attached to the camera. It is not something professionals do in post, it is how they film. Video camera lenses are generally designed to avoid this phenomenon, but it can be replicated with some cameras.

Basically, zoom in as far as you can, then frame your shot. The closer the subject is to the camera the shallower the depth of field will be. If you have full manual control on your camera, then keep the aperture as wide as possible as well, this will help.
Posted: Thu, 27th Nov 2008, 9:29pm

Post 3 of 5

Lerman Productions

Force: 410 | Joined: 14th Jul 2008 | Posts: 72

CompositeLab Pro User

Gold Member

But what about when the focus is changed? Like when the focus is on one person and then is switched to the person next to him. Is that done afterwards? How?

For example; in the show Heroes, in the most recent episode, everything around Suresh is blurred except for him. Then Mr. Patrelli starts talking and Suresh gets blurred out. The focus moves to Mr. Patrelli. I doubt they use a program and trace him with a mouse cursor every time he moves. What do they do? How can I do it?
Posted: Thu, 27th Nov 2008, 10:12pm

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

No, that is done using the manual focus ring on the lens, which controls how far away from the camera the point of focus is. It is called racking focus.

See if one of your friends has a decent SLR camera, with interchangeable lenses, that they will let you play around with a bit, or better yet, have them show you basically how to use it. Or, ideally, see if you can take a class on basic photography somewhere. Once you understand how a lens works and how to use one, all the depth of filed and selective focus stuff will make more sense. There are plenty of books on the subject as well, but you'll get more out of them if you can have a lens in your hands to experiment with while you read.
Posted: Thu, 27th Nov 2008, 11:46pm

Post 5 of 5

Lerman Productions

Force: 410 | Joined: 14th Jul 2008 | Posts: 72

CompositeLab Pro User

Gold Member

oh, ok. Thanks.