I filmed an amateur theatre production in September and completed work on it in October. Unfortunately, I received a note from a cast/committee member about a scene, querying why a particular group's dresses had changed from blue to purple! They even sent a couple of dslr shots showing the group's dresses to be dark blue, but in the video I shot, it really did come out as purple! I certainly don't recall the colour of the dresses from that night on stage, so, I was none the wiser while editing!
I've never had this problem before, but luckily, with the secondary colour correction tool, I was able to mess around with it and correct it back to a blue colour. Not the same, sadly, but close enough. I have wondered if perhaps the stage lighting helped alter the colours, but, the stage lighting seemed very boring and yellow-ish. No other coloured lighting was used throughout the entire show.
Anyway, long story short, how can this kind of thing happen? I can't think of any particular settings that would cause this problem. However, maybe I missed something somewhere. Btw, I use three Blackmagic Pocket Cinema cameras. Hmm... I do remember forgetting to set the colour temperature. Each cam was set to 5600K. Could that turn a dress a different colour?
5600K is pretty cool for stage lamps that are not "Daylight" LED. If the stage lamps were tungsten, you had your white balance off, should have been more like 3200K. This would add a lot of RED to the scene.
RED + BLUE = Purple
If the stage lamps were colored a red tone, then again red+blue=purple.
the light is not comprised of pure red, nor the material a perfect blue. If it were, the dress would have appeared black under the RED + BLUE material. So the material reflected some of the light back which was predominantly reddish.
Shoot a white card, or color balance to a medium grey card before shooting in those condition. A color "chip" chart would be the best.
Thanks for the reply, Aaron. This is the confirmation I needed! When I posted this question, that was the first time I had even thought of the colour temperature. Such a simple thing to forget to do, but, with lasting results. Sure enough, when I check the raw footage with Vegas' Vectorscope, it definitely pushes more towards red.
I have a white card and carry it wherever I go. But, for whatever reason, I didn't test with it. I think, from here on, I will always remember to use it! Btw, I've also done a little digging and found some phone apps for checking colour temperature, so, that will also be used from here on.
Sony Vegas' CC tools were very handy in fixing things up to look good, but, it's always good to be reminded that there's work to be done with our cameras that could save time and money in the long run. Thanks Aaron :)