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blue screen and cam diffusen


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#1 Ram Shani

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Posted 13 February 2006 - 11:45 AM

hi

i am shoting promo for t.v. its talking heads in blue screen

is it ok to use camera diffusen like promist or soft f/x

i have heard that its not recommended to use diffusen for blue screen work

i am shooting with the sony 790 digi beta
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#2 David Mullen ASC

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Posted 13 February 2006 - 11:49 AM

Don't use diffusion - you want clean edges around the subject. You'd want to instead add digital diffusion to the final composite if necessary.
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#3 Stephen Williams

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Posted 13 February 2006 - 12:08 PM

hi

i am shoting promo for t.v. its talking heads in blue screen

is it ok to use camera diffusen like promist or soft f/x

i have heard that its not recommended to use diffusen for blue screen work

i am shooting with the sony 790 digi beta


Hi,

Back off the detail first!

I don't recommend diffusion unless you can test the post path first, it can work with some compositors but others will cry!

Stephen
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#4 Phil Rhodes

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Posted 13 February 2006 - 12:11 PM

Hi,

Avoid.

You may find it's possible to pull a key because the spill correction should catch any blue that's diffused into the foreground, but what you'll then have is a diffused subject comped into a sharp background, or you'll have to try and match the diffusion, and get the edges of the subject to diffuse correctly into the background without diffusing them into the foreground...

It may appear to work but it will be a nightmare scenario if you need realism.

Phil
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#5 Ram Shani

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Posted 13 February 2006 - 02:04 PM

hi

thanks for all the answers i will not use diffusen an the cam insted i will use super soft light on the faces

anther q: for movment i need to do marks on the blue screen like crosses but could thay be in any color?

Edited by ramdop, 13 February 2006 - 02:04 PM.

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#6 David Cox

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Posted 16 February 2006 - 01:44 PM

anther q: for movment i need to do marks on the blue screen like crosses but could thay be in any color?


Depends precisely on the shot, but assuming you need the background to move in the same way as the blue screen then yes you should have tracking markers. However, be aware that if these markers are not blue, they need to be removed by hand in post and this can be very time consuming. A very good trick is to have a different shade of blue marker on the blue background. If you can clearly see the two shades, then the tracking software will also see the markers. If you can see that both shades are definitely blue, then keyers will get rid of the markers as the whole shot gets keyed.

How many tracking markers you need depends on your movement. You only need one if your movement is planar (2D) without Z rotation. You need two trackers as far apart as possible if you are rotating the camera (Z rotation) and many trackers in a grid of a known size if you are adding a 3D background with true camera moves.

David Cox
Baraka Post Production
www.baraka.co.uk
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