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Old August 6th, 2003, 08:33 AM   #31
 
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as , I'm sure you're aware, white balancing is about setting the color temperature calibration of your CCD or CMOS. Everything is relative, eh? When you white balance in the sun, the color temp is for bright sunlight, yes? About 5200 deg K? When you white balance in the shade the color temp is about 7200 deg K. Also, shade provides a lot more diffuse light, as opposed to sunlight where you get a lot of sprectral reflection which can mislead your calibration.
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Old August 6th, 2003, 08:44 AM   #32
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But if the subject you want to shoot is in full sun, shouldn't you calibrate in full sun? How do I get around the problem of my GL2 not locking in the white balance when the white balance card is too bright?

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Old August 6th, 2003, 09:07 AM   #33
 
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that's the reason i suggest using a gray card. the gray card won't give you a luminance value that blows out the sensor in full sunlight. I think you'll find, if you experiment a little, that there is a slight shift in the color balance of the recorded video if record in sunlight vs shade. Sunlight has a high RED component, which drives the overall color balance too blue for my taste.
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Old August 6th, 2003, 09:09 AM   #34
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ok.. if you say so.

I stand corrected then..
I don't really think so but...
I apologize if my info was incorrect.
I just don't see how your camera can get to a balance of white unless the object it balances on is white..
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Old August 6th, 2003, 09:12 AM   #35
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Thanks.. I am going to check this out

With my DP friends and see what they say about it.
Thanks for the info.
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Old August 6th, 2003, 09:13 AM   #36
 
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Richard...

gray *is* white...only the luminance has been reduced. the color sensing part of the sensor can't distinguish between white and shades of gray.....it shows up simply as luminance with no color info
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Old August 6th, 2003, 09:21 AM   #37
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I believe Bill I believe.. grey is white.. white..

Yes.. I understand what you are saying.
I guess I never had a problem with white and since I come from film background I just.. you know put grey with exposure..
<My profound apology for any misinfo I gave.
I did not mean to
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Old August 6th, 2003, 09:28 AM   #38
 
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LOL...
not to worry.....
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Old August 6th, 2003, 11:16 AM   #39
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These last posts were pretty good ones. While everyone is still reading this thread:

1. You can balance with a grey card. A grey card is really white with equal RGB values (reduced luminance). This may even be desirable if lighting is very intense.

2. Using white for white balance is very handy since any white object in the shot, can be used to rebalance the camera.
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Old August 7th, 2003, 02:11 AM   #40
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If anyone is STILL reading:

I've always used white for the white balance, simply because there's always something white nearby (usually a sheet of paper). I agree that in theory there's no reason why a grey card won't work, it's just another thing to hump around with you.

If you are in a situation where the camera cannot iris down to a white surface i.e. it "blows out", my feeling is that you are shooting at too high a stop to begin with. If, say, the maximum aperture of the lens is f22 and your proper exposure is f16 on the subject, a white card may well overexpose if you zoom in and hit "auto iris" as it bangs to a stop at 22 while wanting to continue on to 32 (which would be next if the lens had it).

What's the problem with shooting a tiny aperture? Similar to shooting wide open, you are not at the "sweet spot" of the lens, and chromatic abberations can occur as a result (color fringes). Also, you've got no-where else to go in case you have to stop down more--what if that subject suddenly dons a white sheet, for instance? It's a ghost movie, I guess...

Anyway, the ideal is to add some ND or go to a faster shutter speed (less ideal) so that the lens perches at no more than an f8--this gives you plenty of room for opening up or stopping down the iris due to clouds, shade etc.

And another thing: I too white balance in the shade so that the overall image tone is warmer, it almost always looks better unless you are going for an effect. Under these circumstances you are likely to be at a more comfortable f-stop and the white won't blow out anyway. The exception would be at sunrise or sunset, when the shade is exceptionally blue and the sun is exceptionally orange, in which case you may be best off using a preset daylight or cloud setting, or using one of your pre-existing midday white balances if they are still available in memory.
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Old August 7th, 2003, 08:22 AM   #41
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Charles,

Yes, I'm still reading! :)

Thanks, that was helpful. I think that's exactly what's happening, my camera trying to close down more than it can, but still blowing out the whites. I've tried the ND filter setting on my GL2, and that helps, but sometimes I still have to go to the shade. I didn't think of manually stopping down the camera. I usually have it on auto or shutter priority. I suppose full manual would be better, but I'm still learning this stuff.

Trying to shoot around f8 makes sense to me. I'll have to keep that in mind.

Thanks again!

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Old August 7th, 2003, 08:30 AM   #42
 
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the problem with "white" is that the human eye can't easily distinguish polar white from eggshell white. Ergo, a white balance calibration error occurs. An 18% gray card is "calibrated" so there can be no mistake.

I use RAW image software processing program called Capture One. C1 has a tool that allows sampling part of the image to determine white balance. The software will give feedback concerning the "quality" of the white being sampled. It's incredible how much "white" really isn't white. I think there's a lesson in that observation.
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Old August 7th, 2003, 09:10 AM   #43
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Okay, here's another revision--

1. You can balance with a grey card. A grey card is really white with equal RGB values (reduced luminance). This may even be desirable if lighting is very intense.

2. Using white for white balance is very handy since any white object in the shot, can be used to rebalance the camera. White balance in the shade, if possible. Use ND, aperture, and shutter to bring the exposure down before white balancing.

3. For sunrise or sunset use a daylight or cloud setting.

-----------------------------------------------
Skipping the sweet spot discussion, how critical is the color of white for balancing?

Charles, besides logistics what are the downsides of using a gray card? Would there be noticable differences between video that had been balanced on a properly exposed gray/white card?
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Old August 7th, 2003, 09:13 AM   #44
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Bill, from a theoretical standpoint I can certainly understand that concept, and that an 18% card will eliminate that uncertainty.

I only wonder (and this on a practical level) if the difference between shades of white is as relevant to the vast majority of DV users. Given that different brands of camera have a vastly different color rendition, let alone different models within each brand, there's already a vast range of what is considered "calibrated" video.

Attending my first true tape-to-tape color correction session years ago, I was stunned to learn just how green the Sony standard is (this was using a Betacam). The camera was properly calibrated and white/black balanced, even with "cheated" white balance to improve skin tones, but it wasn't until I saw the before and after versions that the colorist dialed in that I came to realize how far off the "standard" is. I've since heard various theories over the years why Sony cameras tend to the green.

So, playing devil's advocate a bit, is not the color correction process every bit as or more important than assuring a perfectly neutral target; or is it more relevant to select a target that will "cheat" the white balance to a more desirable tone (something like the warm cards, although I would want to add some green into the mix to overcome the stated problem above)? Certainly agreed that a consistent target is desirable.
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Old August 7th, 2003, 09:19 AM   #45
 
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I agree with you, completely, Charles. It seems a lot of newbie's are hung up on trying to define a "standard" of calibration that doesn't exist in prosumer or consumer level equipment. It's akin to buying $5000 stereo speakers for a Radio Shack stereo system.

At any rate, my own process is that i've found some "colored" white balance cards that biases my white balance in the way you sugested. Works great, and I'm very pleased with my results.
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