[Tig] a question about grads.

Kevin Shaw kevs
Thu Dec 30 16:33:53 GMT 2004


on 30/12/04 3:56 pm, Rob Lingelbach at rob at nccom.com wrote:

> how are you proposing to add the grain at that point?

Usually "stretching" the image enhances existing grain - Gain stretches more
than lift, and different devices treat Gamma in different ways. What color
corrector are you using?

On a 2K Plus the simplest way would be to use a secondary window, or a
channel window, grad the window from the horizon and isolate the sky. The
grad will make the isolation easier. Now increase gain and lower lift (exact
controls depend on whether your are in Kilovectors or channel. I know gain
makes the image brighter, hence the need for a well exposed OCN. Basically
you are over darkening with lift, then correcting the correction with gain.

Probably best to keep the telecine grade quite low - set it for the whites
to be lower than usual. As long as the blacks are not clipped, it should
expand back nicely in the color corrector

If you need more control use 2 vectors or a vector and a channel. Darken the
sky in one (using gamma and lift as much as possible) and brighten it in the
other using a little gain. Using lift and gain in this way expands the
dynamic range and enhances grain structure. The second correction (usually
gain) does not have to have the same isolation as the sky grad - could be
global, which would help if you are back lit.

You can also try raising lift slightly and lowering gain, to get a flatter
but darker result. The grad from the window will probably be more
pronounced. However, this will likely reduce the grain, esp. on Vision 100T

Not sure how easy this is to follow, it is easier to demonstrate.

There are other good options, adding grain in a workstation, or keying in
grain using the colorist toolbox noise generator for example. But using Gain
is simplest.

Good Luck
Kevin

Kevin Shaw                 consultant colorist
kevs at finalcolor.com          www.finalcolor.com
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