Hi ive used a polygon plane as a layer for shadows to be cast on from text in my small scene. The problem is that when i add a lambert onto the plane and try to make the lambert white ( so as to make it easy to change to multiply in after effects) the lambert seems to stay grey. In my scene ive made about 5 shots and strangely the first shots lambert is white when i render it out, yet in the shots after that i cant seem to get the lambert to go white.. any ideas on why this might be? Ive pasted the same light, polygon plane and plane shader into each shot so as far as i know the settings are the same.
I'm not sure why the plane is rendering differently in each case, although I wonder if it has to do with your 'copy and paste' workflow. I'm not sure if you mean you literally used the Copy and Paste commands, or if you exported and imported the nodes in question. Copying and pasting is generally NOT recommended, especially for lights--they tend not to work properly when pasted.
In any case, if you are trying to capture shadows, it is generally recommended to use the 'Use Background' shader for this task instead of a white Lambert. The shadow will show up in the alpha.