White balance to a projector and person

Question

Level 1

0 points

White balance to a projector and person

Hi, I am hoping someone could help me regarding this problem.

I often shoot a lot of lectures where a person is up on stage talking with a powerpoint. I configure my white balance on the camcorder to the light that's going to shine on the person (a warm yellow light).

While the person looks great, doing this causes the projector/powerpoint to appear bluish. Normally I would later go and correct this in FCP.

Is there a method to set a white balance where both the person and the powerpoint will be the correct color? I would prefer not to use automatic white balance (since when I pan from the person, to the powerpoint, and then back to the person, there is a noticeable color change on the person).

I shoot on XL1's. Thanks for the help.

Mac Pro, Mac OS X (10.4.9)

Posted on Nov 13, 2008 10:56 AM

Reply

Answer 1

Nov 13, 2008 11:08 AM in response to Lantis

You might see if the projector has a color balance setting that can be changed...really not sure about that.

I remember adjusting a plasma for a film shoot once, but have never tried with a projector.

To match correctly, there'd have to be a significant change in the projector, or possibly the laptop output..?..

For our purposes, depending on the project, I either color balance the camera/projected image in post, or ask the presenter to provide digital files, to be used in post.

This is the best solution, but takes more time. And remember that projected images are rarely created with screen safe or title safe in mind, so usually some adjustment needed there as well.

K

Reply

Answer 2

Lantis Author

Level 1

0 points

Nov 13, 2008 12:00 PM in response to Kevan D. Holdsworth

Thanks for the response Kevan. Having them provide me a digital file for post is a good idea, I hadn't thought of that.

To save some time however, I still wish there was a method to compensate for the color balance of both the speaker and the projection. I just tried white balancing to the 'projector's light' but this causes a person's skin tone to be way off.

Automatic white balance works reasonably well (person's skin tone and the projection is a good color). The problem with this is that the color tends to change periodically, especially when panning, making things even more problematic in post. I'll continue to experiment different methods, but still looking for help!

Reply

Answer 3

Zebulun

Level 5

6,749 points

Nov 13, 2008 12:43 PM in response to Lantis

You need to have the color temps of both illumination sources match. Or, continue to use your auto white balance but lock the auto white tracking. Most cameras worth anything will allow you to lock the auto white tracking.

Reply

Answer 4

Nov 13, 2008 2:33 PM in response to Lantis

To save some time however, I still wish there was a method to compensate for the color balance of both the speaker and the projection. I just tried white balancing to the 'projector's light' but this causes a person's skin tone to be way off. < </div>

sounds like the projector is balanced for daylight, which is stupid, but that's the accepted convention, somewhere between 4200K and 5200K, which is close to the white balance of a computer monitor.
The stage lighting is tungsten, 3200K.

All modern graphics projection systems have a white balance control, you just have to find it, and then you have to convince the operators to let you change it.

Here's the problem, though: as soon as you change the white response of the projector to match the stage lighting (or to get it a bit closer) the carefully designed color scheme of the prezo changes. This can be quite severe. Coca Cola "red" can shift to maroon or mud and this can really upset some folks.

bogiesan

Reply

Answer 5

Nov 13, 2008 2:37 PM in response to David Bogie Chq-1

How about gelling the light sources (CTB) to better match the projector?

Don't know how viable that would be, but worth a shot. (as long as you don't have a bunch of varied light sources...tungsten/flourescent/sodium vapor...etc.)

K

Reply

Answer 6

Nov 13, 2008 2:43 PM in response to Kevan D. Holdsworth

How about gelling the light sources (CTB) to better match the projector?< </div>

Applying a slight blue filter to the tungsten lights might help but then your speaker's skin tones go all wonky from the audience's point of view.

If you can, put a white slide in the PowerPoint gate. Place huge white card on the stage where the projector will hit about half of it. Shine the stage spot light on the other half of the card. Borrow a color temperature meter from a film nut and read the differences between the two light sources. Or just white balance on one half, shoot some tape, and then the other half, shoot some tape, and observe how wide the range is. If your camera has manual WB, set it someplace between the two extremes.

bogiesan

Reply