I'm trying to put a filter on the top 1/3 of a clip to darken the sky.

Any guidance would be appreciated.

you better will create a mask out of the sky.
convert video to B&W using histogram, you will isolate the brightest part and using some rectangular cache you will cut the bottom part of the picture.
with this mask you can apply all effects you need to the sky only.

why not just drop a TGA with graduated alpha on . make in PS

for a filter you can dupe the clip to the track above,
filter it as needed
generate a matte in PS - black to white gradient, hard edged shape, whatever. save as TGA
put Make Alpha filter onto clip in FCP that you CC'd
place matte TGA into video well of filter and then select the appropriate option like LUMA to generate the matte

or

you could use Pixel Chooser in any of the BorisFX BCC filters which has built in shapes, channel mattes ( luma, alpha, invert luma, R,G B ) or still use an external matte image and do the same thing directly to the clip you need to work on. BCC pixel chooser rules for this kind of work.

or

you can use the secondaries in the 3 way color corrector to make the matte and CC

or

you can send the clip to Color

or

you can send the clip to motion to mask & CC

or

you can export the clip to AE to mask & CC, import rendered clip

or

you can dupe the clip twice above the original.
in the top most clip do whatever to turn it black and white so that you get white where you want to key, contextual menu "disable clip"
on the clip below, CC is as you need, then right click it and use composite mode ->track matte so that the middle clip uses the top as the matte

I'm sure there is at least another way to two to do this

you're welcome to grab my gradient filter and give that a go if you like:
http://web.mac.com/andymees/Free_and_Easy/main/Entries/2008/5/20_Andy’s_Gradient_Filter.html

Andy,

Super plug-in; very simple but *extremely* useful. I've been recommending it to my clients ever since you first posted this in a different thread.

Thanks Robert

Hi Andy, this looks like a handy filter. Quick, stupid question, do I just drop this filter into my FCP plug-ins folder or is there another place for it?

Thanks.

Try Dominik Seibold's Contrast Filter.
It might be of big help for you.


P.


http://www.dominik.ws/DominiksContrast.fxplug.zip