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Old November 15th, 2006, 09:55 AM   #1
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Exposure and wb in changing lighting conditions

Due to the vast amount of information and the willingness of amazing individuals to share their experience, I have been able to startup a video ministry at my church in 1 month. We have been recording services for 3 weeks now. Still kind of rocky, but it is moving forward nicely.

I purchased 2 Sony A1U cameras which are awesome cameras. I am sending a feed from each camera to it's own DVR in the control room where I can now (as of 1 week ago) direct camera angles and movements.

I am having issues with white balance and overexposure however, and I was hoping for some tips.

The "main" camera is left of center upstairs above the stage at a distance of about 75 ft (line of sight). The Floor camera is far left of center at a distance of about 30 ft.

The floor camera is the one causing problems. The white is washing out, (easily seen at kbbc.org, click "watch last weeks service" from home page) and it is overexposed.

If I set white balance manually with one push, it is great until they lower the lights, or raise the lights. So I have been setting it to auto. If I use Zebra and set the exposure manually until all of the lines are gone, the image is far too dark, or it's great for the light setting that is full up, but then too dark on certain other cues, so I set the exposure to auto.

Is there a correct way to manipulate these settings in a changing lighting environment? Is it best to use auto for both of these modes? Should I have my camera operators adjust as the lighting changes?

Your expert opinions and recommendations are greatly appreciated.
Joel Chappell is offline   Reply With Quote
Old November 15th, 2006, 10:06 AM   #2
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You could try TV mode where you let the camera adjust the iris as needed without going into added gain. Much testing required for this. When the lights change have a cutaway or overlay from a computer that you can go to so the audience won't see the shift in iris.

As for white balance, you will need to determine the most common indoor lighting scene and set all cameras on a white card at the same location. If your mixer has a master colour corrector you could get into that once you have more experience with the various colour temperatures.
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Old November 15th, 2006, 01:23 PM   #3
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Well, you've got a complicated situation, and most video professionals would start with negotiating with the lighting people to make it simpler.

Obviously, the changing color temp is a problem. When lights are dimmed, they get much warmer (more towards the red). Could lighting for the service be planned so that the minister was always in a full-intensity light? That would probably be step 1, keep the center(s) of attention in consistent color temperature, and let the audience lighting go warm. White balance manually at the podium or altar.

If this just can't be done then auto white balance really would be the best choice, and most prosumer cameras will do a reasonably good job with this... depending on how mixed the color temps are in the scene. In other words, if the minister is lit with bluer light than the audience, the camera will change the auto white balance depending on where it's pointed.

You're using Zebras wrong. Not familiar with your specific cam, but most sony cams have selectable 70% and 100% zebras. At 70%, you'd want zebras showing on the key light side of caucasian faces. At 100%, you'd want them showing on anything that is white, but, you have to be careful and slide through several exposures to assure that you're not totally blowing out and losing detail in white objects. You should be able to see this on a good monitor in your control room. A good monitor, properly set up, is indispensable in this situation.

As to varying light levels, again, it would be helpful if you could develop a specific lighting plan. In almost all situations manual iris, shutter, and gain is better than auto. For example, you probably don't want the exposure to change when you zoom out from the well-lit minister to include the poorly-lit congregation, which would happen on auto iris, shutter, or gain.

No matter how you do it, it seems like there is some education and goal-setting that needs to take place. To do this well, you need to know more about video and lighting. Your camera operators need to know more about manual controls and how to work with zebra. Perhaps most importantly, the minister and/or board or other decision-makers need to determine what's most important in compromising between the quality of the video and the status quo on lighting, because video cameras see the world differently than the eye does, and just don't cope well with large variations of intensity and color temp.
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Old November 15th, 2006, 08:03 PM   #4
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Quote:
Originally Posted by Seth Bloombaum
Obviously, the changing color temp is a problem. When lights are dimmed, they get much warmer (more towards the red). Could lighting for the service be planned so that the minister was always in a full-intensity light? That would probably be step 1, keep the center(s) of attention in consistent color temperature, and let the audience lighting go warm. White balance manually at the podium or altar.
I was thinking of trying just what you recommend here... setting white balance at the podium with the light settings for the main event which in this case, is the preaching.

Quote:
Originally Posted by Seth Bloombaum
You're using Zebras wrong. Not familiar with your specific cam, but most sony cams have selectable 70% and 100% zebras. At 70%, you'd want zebras showing on the key light side of caucasian faces. At 100%, you'd want them showing on anything that is white, but, you have to be careful and slide through several exposures to assure that you're not totally blowing out and losing detail in white objects. You should be able to see this on a good monitor in your control room. A good monitor, properly set up, is indispensable in this situation.
I'm using 70%, and I usually like to close down to just where they begin to go away. I think I have overcompensated like you suggest, I will test this also.

Quote:
Originally Posted by Seth Bloombaum
As to varying light levels, again, it would be helpful if you could develop a specific lighting plan. In almost all situations manual iris, shutter, and gain is better than auto. For example, you probably don't want the exposure to change when you zoom out from the well-lit minister to include the poorly-lit congregation, which would happen on auto iris, shutter, or gain.

No matter how you do it, it seems like there is some education and goal-setting that needs to take place. To do this well, you need to know more about video and lighting. Your camera operators need to know more about manual controls and how to work with zebra. Perhaps most importantly, the minister and/or board or other decision-makers need to determine what's most important in compromising between the quality of the video and the status quo on lighting, because video cameras see the world differently than the eye does, and just don't cope well with large variations of intensity and color temp.
I just had some training with my operators last night. We went over all of the manual functions that we are discussing here. I believe now that they have a better understanding of how manual features work, I will be able to experiment more following your advice.

I appreciate your input. I am relatively new to video, and my operators are below that. It's amazing we have pulled off what we have. I attribute it to the quality of the Sony A1's and the help of Vegas 7. 1080 HD video makes a terrific output even with color balance out of whack.

Thanks
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