On 24 Sep 2008 at 20:16, Gordon JC Pearce MM3YEQ wrote:
  Sounds like you can hardly make it worse. 
I'd be sore tempted just to "eyeball" the adjustments, myself.  I
imagine a photometer is essential if you care about things such as
color accuracy, but perhaps just checking white balance may be close
enough.
Cheers,
Chuck