White Balance: White vs Gray Card

S

stephenbuck

Member
Does anyone know which type of card produces the most accurate white balance with the DVX100: white (say a sheet of foam core) or gray (say a Kodak photographic 18% gray card)?

I've seen numerous opinions about which is better and can't seem to nail down the correct answer.
 
Re: White Balance: White vs Gray Card

White, definitely white.  I have no idea why anyone would use a gray card to do a WHITE balance :-).  While a gray card might work, the camera will have an easier time correcting off a white card, especially in low light.  I think this misconception fits in with the huge amount of misinformation about exposure floating around in the world of video.  I have read the most unbelievably bad advice concerning exposure for video.  Everything from complete misunderstanding of the zone system--which has NO application in video to complete cluelessness on how to set and use zebras or exposure meters.  Sorry, I don't mean to rant, but it makes me crazy to read some of this stuff.
 
Re: White Balance: White vs Gray Card

An 18% Gray Card is typically used to help establish exposure.

Basically, the 18% Gray Card would be placed in the main area of the scene where the light hitting it would be read with a reflective light meter.

If you exposed for something that was 100% white (like a bright white sheet of paper), then the rest of the scene might be rendered dark. Likewise, if you exposed for something like... a dark Gray Card... then the rest of the scene might be overexposed.

The 18% Gray Card comes close to approximating the reflected luminance that might come from caucasian to medium skin tones.

If you point a spot meter at a mountain full of snow you'll get one reading. If you point a spot meter at a 18% gray card (in the same lighting) you're exposure will not be fooled by the bright, white snow.

I know what I'm talking about but sometimes I don't pick the right words to help me express my thoughts.

Barry, please crystallize my thoughts. ;D
 
Re: White Balance: White vs Gray Card

There is definitely a lot of confusion. Many sources do recommend a gray card for white balance but don't explain why. On the other hand, many sources recommend a "white" sheet of paper or foamcore. Perhaps it's because a proper gray card would be a more consistent reference than varying definitions of "white"?

I've also seen lots of talk about white balancing at the camera using something like ExpoDisc (www.expodisc.com)? Others have even mentioned styrofoam cups, coffee filters and pringles lids!
 
Re: White Balance: White vs Gray Card

I'm not confused on concept, just verbage to express such.

I still say 'white is right'... for WB anyway. The 18% gray card was originally established primarily for still photographers using reflected light meters to establish EXPOSURE.

Any use of said gray cards for white balancing a video camera came way after that fact.

As for your ExpoDisc, styrofoam cups, Pringle's lids, etc... sure, I've seen all kinds of WB tricks and even used some in a pinch.

The simplest and quickest way is to point the lens directly into the light source. Zoom in. WB.

Of course, this is for run and gun ENG type stuff only.
 
Re: White Balance: White vs Gray Card

[quote author=Terry_Lasater link=board=news;num=1081808632;start=0#2 date=04/12/04 at 21:04:16]

Barry, please crystallize my thoughts. [/quote]

Sorry, Terry. I've been trying to crystallize my thoughts for years, but the best I can manage is something the consistency of Jello pudding :-)

A white card, a white sheet of paper, a piece of foamcore, white cotton panties--all these objects will work fine and take up very little space. While there may be small variations in the shade of white it will have very little effect on your white balance. Any slight variation can easily be compensated for when you do your final color correction.

I would not point your camera directly at a light source to white balance for fear of frying the CCD's. Even if you don't fry them, they'll probably be overloading and the camera may not be able to white balance properly.

You don't need a gray card with a video camera and if I see you with one I'm going to take it away. Repeat this mantra as often as necessary--The zebras are all I need...ohmmmm...the zebras are all I need...ohmmmm.
 
Re: White Balance: White vs Gray Card

Oops! Sorry Barry_S. I actually meant for Barry Green to crystallize my thoughts. :-[

Although, I do respect your insights, too... I didn't notice your post was right before mine. So, naturally you would assume I was talking to you when I say "Barry... ". Sorry.

Yeah, BTW... I do not recommend WBing in the aforementioned run and gun methods.
 
Re: White Balance: White vs Gray Card

Okay, I'm with Barry_S on all he said, except I'm not so sure about the panties thing...

I always use a white card to conduct a white balance. Technically I guess a gray card might work as well, if it's perfectly neutral gray, but... well, I guess it might work... hmm. Have to try it. But again, as Barry_S says, there's really not much reason to use a gray card when working in video.

A gray card is a sort of a way to turn a reflected-light meter into operating more like an incident meter. By giving a neutral 18% reflectance, the light bouncing off the card should give the same reading to a reflected meter (such as the DVX uses) as you would get if instead of holding a gray card, you were holding an incident meter there.

(how's THAT for crystallization? Probably the most confusing sentence I ever wrote!)

White balance requires a good white reference, and a gray card would have some limited value if you were a light-by-incident-meter-type of shooter. Other than that, no real purpose to having a gray card on a video set, is there?
 
Re: White Balance: White vs Gray Card

Just to make clear... I am not promoting the use of a gray card for white balancing.

Other than that... we seem to all agree (Terry and the Barrys). Hey, we should start a band! ;D
 
Re: White Balance: White vs Gray Card

I loooooooooove the Barbarterry Three !!!

Hope a Larry won't join you : the name of the band would greatly suffer from his arrival (Larbarbarterry Four ? Barbarlarterry Four ? Barbarterlarry Four ? Yuk ! It sucks man !)

Especially if this guy Larry is accompanied by his sister Mary...

My advice : a trio is a more successful formula — and there's gonna be more girls and royalties for each of you three.
 
Re: White Balance: White vs Gray Card

Well... I've got two serious problems regarding the white cotton panties :

1. My wife only wears thongs, and there isn't much material on those things to do any kind of balance.

2. Can a black thong be used for black balancing ?

OK, OK. I won't do it again. Promise. ;D
 
Re: White Balance: White vs Gray Card

OK, I just had to add another Barry.

Can someone explain the details of the white balancing algorithm? My assumption is that it just analyzes the R,G, and B and adjusts to make 'em even.

For this, I don't see why there'd be any difference between a white or gray target...?
 
Re: White Balance: White vs Gray Card

Okay, what is with the DVX and Barrys? I have hardly ever met another Barry, yet in this forum there's at least four or five... ;D

... and, that's why I said it might work. If the gray is perfectly gray, and thus the camera balances the light to get even r,g,b response, it might work. Worth a simple test at least...
 
Re: White Balance: White vs Gray Card

Barry, you're right of course, and so is Barry. When you white balance the camera, you're telling it, "here's a reference that has equal amounts of red, green, and blue. The camera measures separate voltages from it's red, green, and blue circuits and balances them so they're equal.

However, the camera's white balance circuit can't tell the difference between white or gray. Think about the amount of light reflecting off of a white card outdoors in full sun vs indoors. There could be 8-10 stops difference--*more* than the difference between 18% gray and white under identical lighting conditions. To the camera, gray just looks like white in a lower level of light.

So why use a white card? Because a white card will produce higher voltages for the white balance circuit. Indoors or in dim light the white balance circuit will have cleaner information to work with--a higher S/N ratio. Not to mention, there are zero advantages to white balancing with a gray card.
 
Re: White Balance: White vs Gray Card

Oh, now I'm thinking of changing my login to something more appropriate with "Barry" in it. It's true, I've met maybe two other Barrys in my life. But here - and, I'll have you know, in Pro Audio groups as well - we seem to abound. I guess we're technically creative people...

Anyway, the Gray Card thing it seems is as I thought. Anyone try those "Warm Cards"?
 
Re: White Balance: White vs Gray Card

Just a quick factoid - the white balance does not make the RGB channels equal - each of the levels are are changed in order to remove color temperature from a scene to be perfect white. If the RGB channels were always equal, then you are always in a perfectly balanced white "tungsten" based world. Video CCD's are tungsten in their native state and are corrected by the RGB to balance for all non tungsten state of light.

I believe the word "equal" is meant to create "equal and balanced white" and not referring to the actual channels. Think of a graphic equalizer for sound, the sliders are not euqal when baklancing out a room, but the sound in the room is balanced... The RGB channels are the same way for color.

Michael
 
Re: White Balance: White vs Gray Card

Good grief, Charlie Brown.

I've been a videographer for 17 years and I've never had to worry my purty li'l head this much over such a simple procedure.    ??? ::) ;) ;D
 
Re: White Balance: White vs Gray Card

ullanta-

There was a thread awhile back on the warm cards. Some people bought them, some people made their own. John Hudson made his own by sampling the color data and printing his own in Photoshop... so did I. It works just as well as spending 90 bucks for the "real" ones. They do give you a nice warm image. Same effect as white balancing through lighting gels over the lens...
 
Re: White Balance: White vs Gray Card

I've used the lighting gel sampler over the lens for years to white balance. It's easier (they fit in my shirt pocket) and much more accurate IMHO. I can use a quarter to half blue to warm up the image and 1/8 to 1/4 green to remove the green cast (if necessary). I can also use the green gels to neutralize and give me really nice skin tones under flourescent conditions. With the gels in varying intensities, it provides me with much more control than a pack of expensive cards. Oh yeah, the sample gels are free. In a pinch, I white balance on clouds in outside conditions with just enough blue sky included to warm up the balance to my preference. Works like a charm.
 
Re: White Balance: White vs Gray Card

Let us not forget that our beloved DVX100 allows us to tweak the color in the menu.

You could WB 'normally' and warm it up via the camera's menu.
 
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