Self-print grey card.

[Marshall]

Does anyone know the R.G.B.values so that you can print out your own grey card using photoshop, to use in setting custom white balance.Grey cards proper seem so expensive for what is after all a coloured piece of card !

[Citizensmith]

How precise does it need to be? I would guess that just printing at 33% gray would be close enough, even given variations in printer output colors. I'd just be suprised if the small differences between color spaces or ink sets would ever add up to much when it comes to the camera deciding whether or not it needs an extra 1/2 stop of light or sommat.

I usually just try and find any mid-tone subject including grass or leaves. They aren't even close to gray but they still have provided good results for metering.

[L Pagan]

here you go
http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=15633&is=REG

[Jon]

Well, to get a proper neutral grey for CWB use, you should have R=G=B. So you'd need to make sure you have calibrated your monitor and printer before you try printing your home-made grey card. I think buying one would be cheaper and easier.

[dennykyser]

I have always purchased gray camera bags for this reason, in a pinch I meter of the bag and have never been far of. I know its not exactly 33% gray, but when needing a quick shot in bright snow covered area, it sure saves a shot.

[pierrot]

If it is a white balance question, use the good ole' coffee filter.

[bimbo]

Try this: R=G=B=128.

[swatcop169]

great topic, I was wondering the same thing. I didn't think it would be to long before someone posted asking about this.

[swatcop169]

Alittle research;

http://share.studio.adobe.com/axAssetDetailSubmit.asp?aID=11119&back=http://share.studio.adobe.com%2FaxBrowseSubmit.asp%3Fc%3D 78

[Jerrytrebec33]

Whats a grey card and whats it used for?

[Citizensmith]

Try this: R=G=B=128.

That would be 50% gray, a gray card should be 33% gray.

White balance on your monitor does not matter at all for this. Unless you'll be monitoring off of the screen. You just need a printer that can get reasonably close.

Personally I think you should be less paranoid and do as another poster suggested and just get a gray camera bag. Its definitely worth having a neutral toned object for metering, but if its 30% vs 33% or has just the wrong hint of blue in it, its not going to mess your metering up in the slightest.

[Jon]

Grey cards for exposure should be 18% grey. And my Kodak 18% grey card comes in at R=G=B=128 of 255, which is about right when you realize that "18% gray" is also referred to as "middle gray". The 18% refers to the amount of incident light that's reflected back, not to the luminance or color values. Perfect neutral grey isn't as important for exposure as it is for (in the original question) white balance. If the grey isn't neutral, you'll be introducing a colour cast to your custom white balance. And since you can get 2x Kodak 18% grey cards (8x10") for $12 at Amazon, and cut them in half, that's hardly going to break the bank. At least if it is, have B&H ship that 300 f/2.8 IS L via 3-day UPS rather than FTL Express ("When it positively, absolutely has to be there yesterday").

[RDKirk]

Does anyone know the R.G.B.values so that you can print out your own grey card using photoshop, to use in setting custom white balance.Grey cards proper seem so expensive for what is after all a coloured piece of card !

That won't work well.

First, white paper itself usually has phosphorescent brightners that throw off color balance.

Second, there is zero guarantee that the black ink won't have an odd spectral balance--especially if your printer uses a combination of colors to get black.

Third, a gray card isn't just a gray piece of paper. The color is made of pigments (not dyes) formulated to reflect 18 percent of the light striking the card, quite precisely. Unlike dyes, the pigment won't fade easily. I've got cards twenty years old that I've kept carefully and still measure exactly with new cards.

Fourth, the purpose for using a gray card is to have a standard against which to develop your procedures. Printing throwaway sheets might seem like a good idea, but every one you print will be slightly different and will throw off your results. The gray cards will be nearly perfectly the same--the one develop your methods by today will be the same as the one you buy twenty years from now.

A caveat: Gray cards are not actually designed for color balance, and very close measurement reveals that they don't have perfect spectral response under all lighting types. But they do work out well in most cases. If you want something more precise, you can check out the WhiBal cards or get a piece of Kommerling Komatex gray plastic material from a sign shop (they'll send you some free samples from their web site). The Komatex has an undeground web cult following for giving good spectral response.

With regard to printing: If you are using Windows on a calibrated monitor at 2.2 gamma, the tone of an 18 percent gray card is 118/118/118, not 128/128/128. I do believe it will come out to 128/128/128 on a Mac.

[Citizensmith]

The 18% refers to the amount of incident light that's reflected back, not to the luminance or color values.

My mistake, I was assuming it referred to color values.

Still, I think I'll stick to using any old mid toned object in the area, or just dialing in some exposure compensation.

[mbze430]

Seriously guys. Here is a $10 idea. WIKO makes a 18% grey handkerchief. Semi-reflective. It uses microfibre so it's lens friendly. So you have a 18% handky + a lens wipe in one small tiny little package that fits in your pocket.

[chris.bailey]

My copy of Scott Kelby's CS book came with one in the back (18% grey one side and white 18% grey and Black on the other)

[tsnow]

Marshall,

I believe that in photoshop you would set your RGB = to each other somewhere between 0 and 255. all 0's is black and all 255 would be white.
i.e.
R=155
G=155
B=155
Printing the gray card is another story since printers use CYMK...

Anyhow,

my two cents

Tony

[ohenry]

Amazing. You buy an expensive camera and expensive lenses and can't pony up 10 bucks for a gray card. LOL...too funny.

[panoramarts]

The Values for 18% grey is:
R= 168
G= 168
B= 168

[themichael]

But is your printer profiled? And does your camera custom balance to white or gray?

Its not just "colored paper", but pigment that is 18% gray under ALL light. Is your printer and paper gray under all lighting?

Goto a local art supply store and buy a tube of acrylic neutral gray 5 paint. Note the 5, as in zone 5, 18% gray. Make as many as you want. about $2 a tube. The better quality paint will have the Lab (colorspace) numbers on it. L=68,a=0,b=0.

Also pick up some pure white, carbon black, and some mat board. Make an exposure cube to play with. Very surprising results. Your meter is stupid and lying to you.

[themichael]

Here's the layout. Cut out and fold. When you paint make sure there are brush strokes. Having some texture lets you know if they are properly exposed. Don't make it smaller that 6" on a side.

http://img293.imageshack.us/img293/155/exposurecubelq4.jpg

Use different combinations of faces. Meter off of one and shoot the whole cube. Light a black side only with a gray and white showing. Meter on the black....

have two black sides showing, light one with the key light.

Try to get texture showing on both the black and white faces.

The cube can also be used for white balance and exposure readings.

[chauncey]

FYI-For some reason all gray cards are not equal. If I put two gray cards in an image, WhiBal and generic, clicking on one will give me a color shift over the other. Using ACR 4.1.

[Desertraptor]

i printed my own grey card on a high end colour copier. Worked a charm but now I cant find it

[PhotosGuy]

First, white paper itself usually... But they do work out well in most cases. If you must measurebate, then yes, there's a tiny difference, which isn't a big factor if you shoot raw & properly expose.

What’s best for exposure, Gray cards, white paper, expensive attachments for the lens?
Gray Card… White Paper. What’s best? (http://photography-on-the.net/forum/showthread.php?t=58677)

Exposure - “Film tricks” can help you out.
Need an exposure crutch? (http://photography-on-the.net/forum/showthread.php?t=89123)