Focus Keying or Blur Keying -> New Technique?

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Most keying is done based on using a constant color or lighted
background, and that background is keyed out digitally by defining that
color or luma value (depending on the approach).

Is there such a thing as focus keying, or blur keying? I was thinking
about how you can shoot video/film with a low-number f-stop and get a
narrow depth of field. In that case, the background would be blurry
and the target of the shot would be focused. I would guess there is a
mathematical or systematic way to build an algorithm that compares
neighboring pixels to find edge pixels in an image by locating the
lines between blurred areas and focused areas. You could then use
those lines to decide which part of the image you wanted to key out.

Would this work? Does something like this already exist?

Thanks for your time!
b

 

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There's motion tracking, where you draw round something in one frame
and the program then tracks it through the scene. Probably more
reliable that the idea of focus tracking, as moving objects that seem
in focus will actually blur in individual frames.

Bernie

 

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<albinocrocodile@hotmail.com> wrote in message
news:1125494892.249207.213810@g14g2000cwa.googlegroups.com...
> Most keying is done based on using a constant color or lighted
> background, and that background is keyed out digitally by defining that
> color or luma value (depending on the approach).
>
> Is there such a thing as focus keying, or blur keying? I was thinking
> about how you can shoot video/film with a low-number f-stop and get a
> narrow depth of field. In that case, the background would be blurry
> and the target of the shot would be focused. I would guess there is a
> mathematical or systematic way to build an algorithm that compares
> neighboring pixels to find edge pixels in an image by locating the
> lines between blurred areas and focused areas. You could then use
> those lines to decide which part of the image you wanted to key out.
>
> Would this work? Does something like this already exist?
>
> Thanks for your time!
> b
>

You might want to checkout www.seriousmagic.com

Luck;
Ken

 

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On Wed, 31 Aug 2005 15:50:09 -0500, "Ken Maltby" <kmaltby@sbcglobal.net>
wrote:

Unfortunately this is going to look like a half-baked situation, as
obviously in reality the amount of unsharpness, depends on how far elements
are from the camera. Blurring a background looks one-dimensionally fake.

You can improve things a bit by using a program like Combustion, which has
Z-planing, where you set certain distances for objects (you will have to
draw a mask around them), and the blur will depend on how far away the
objects are.
Another way to get it better looking, is by renting an adapter like a P+S
Pro-35, where you use 35mm lenses to get your image, with the appropriate
depth-of-field of 35mm.

cheers

-martin-
--

"Beer is life!"

 

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"Martin Heffels" <biz@thisproductworks.com.> wrote in message
news:6v6ch1tcq05b2du6o6j3k04htku19g3ku8@4ax.com...


> On Wed, 31 Aug 2005 15:50:09 -0500, "Ken Maltby" <kmaltby@sbcglobal.net>
> wrote: ***None of what you posted below. *** /Ken

> Unfortunately this is going to look like a half-baked situation, as
> obviously in reality the amount of unsharpness, depends on how far
> elements
> are from the camera. Blurring a background looks one-dimensionally fake.
>
> You can improve things a bit by using a program like Combustion, which has
> Z-planing, where you set certain distances for objects (you will have to
> draw a mask around them), and the blur will depend on how far away the
> objects are.
> Another way to get it better looking, is by renting an adapter like a P+S
> Pro-35, where you use 35mm lenses to get your image, with the appropriate
> depth-of-field of 35mm.
>
> cheers
>
> -martin-
> --
>
> "Beer is life!"

 

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http://www.cs.brown.edu/people/morgan/DefocusVideoMatting/

Sounds like that's what you are after. The big problem that occurs to
me is when you have any large area of solid color in the foreground.
Large solid colored areas will appear identical when they are blurred,
making it hard to say how they should be interpreted...