DIY: Making Your Own Gray Cards
Most cameras are capable of creating 'acceptably good' white balance on your photos. And even if they're failing, you can make a pretty decent guess for what you think the white balance should have been in post production.
But what if you want to take the guesswork out of the equation, and get perfect white balance every time? The professionals use something called a 'gray card' (or 'grey card', depending on where in the world you learned to write English). The name says it all: it's a gray piece of card or plastic that you can use to balance your photographs.
Finding yourself a gray card
Does that sounds a bit high tech? Well, it really isn't - and the great news is that you can use just about anything that is neutrally coloured. Of course, without advanced colour calibration equipment, it's hard to find something that's actually perfectly neutral. For our purposes, however, you don't need to do that: anything that's just about gray will do. Why? Because once you have your photos balanced consistently, it's easy to make sure they are all well-balanced.
The silver on the Macbook Pro is relatively neutral, and can be used as a grey card
You can use anything that is neutrally coloured, but we would recommend using something that's light gray - it gives the camera the best colour reading, and it makes it easier to do your balancing in post production, too. The lids on coffee cups tend to work pretty well, and personally, I've been using my Macbook. The matt, light silver material is relatively neutral, and since I tend to bring my laptop on photo shoots with me, it's always there when I need it.
Printing off a gray card
If you know what printer you are going to be using to print your images, you could create your own gray card as follows:
- Open up a photo taken with your camera in Photoshop. This ensures that the correct color profiles are in your image file.
- Delete the image, and fill the frame with 18% gray.
To get 18% gray, open the colour selector in Photoshop, and choose a
saturation of 0%, combined with a brightness of 82%. That's the correct
color!
- Send the file to your printer, and take it with you on shoots.
The Apple iPhone 4 has a great camera, but it's struggling with white
balance. By using a grey card, I can ensure that the money is
well-balanced. This is the before shot
The key thing here is that your 'gray card' may not be perfectly neutral, but the important thing is that your printer thinks it is neutral - so if you colour balance your photographs to this particular card, your images should come out neutral when you print them next. There may be some difference from printer to printer (some printers may print out slightly warmer or colder images), and this is why gray cards printed on one printer aren't transferrable to another.
It could be argued, of course, that if you're serious enough about white balance that you are going to use a gray card, then you may as well buy a set of gray cards that are definitely perfectly colour balanced, but having a home-made set of cards is much better than shooting without anything, so it's a great place to start.
How do you use a gray card?
By using the known neutral grey as a sample, I can ensure that the photo is perfectly balanced
Whatever you've decided to use as your gray card, the way you use it is pretty simple:
- Set up your lighting
- Place your 'gray card' in the shot
- De-focus your camera a little and take a photo. This ensures that you capture the colour, and not the texture, of your gray card
- Remove the gray card, and take photos as usual. Every time you change the lighting, go back to step 2.
- When you've imported your photos into your favourite software package, use the gray card as a 'sample' to set a custom white balance.
- Copy the white balance across to all the other photos in the set - or until the next time you've photographed your gray card.
You can now sit back in the knowledge that all your photos have the same white balance. If it turns out that it is still slightly off, you could adjust it further, and then copy that white balance profile across to the other photos in the shoot.
Author Bio
Haje Jan Kamps writes books about photography, and has created an affordable set of gray cards, just in case you can't be bothered making your own.
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Comments
Maybe it's just me, but the
Maybe it's just me, but the "balanced" picture has a strong blueish color cast. Do you have a proper gray card to show the difference? IMO, using a self-printed gray card is useless except you have a calibrated printer.
For most of my picture developing, I "balance" the shot the way I want the picture to "feel". Because a perfectly balanced shot gives often a rather boring look. But of course this doesn't apply fully to professional shoots.
maybe it is not just you ...
Seems to me that the before and after have been mixed up ...
I dunno about calibrated printer though, if I print gray then the printer (if not out of ink) will use black cartridge and so the color will be at least neutral if not exactly 18% gray.
re: cards
Oh, my!
Thanks for that embarrassing catch. this is fixed now.
hehe. Indeed, better now!
hehe. Indeed, better now!
I'll agree with Mario--the
I'll agree with Mario--the color corrected looks blue. But I guess you're color correcting to your uncalibrated printer, not a calibrated monitor.
Is it possible you've got the images swapped? The first image's gray card has HSV of 330, 1, 85--pretty darn close to perfect gray. In contrast, the second image's gray card, has HSV values of 221, 27, 90.
One of the advantages of true
One of the advantages of true grey cards is not only their neutral color, but the fact that they only reflect ~50% of the light that hits them. A homemade grey card like this is okay for correcting color, but it can't replace a true grey card for correcting exposure.
This article is highly
This article is highly problematic. Grey cards reflect 18% of light (not 50) and are not considered tool for "white balance" - they are tools to help find optimal exposure.
Yours x Kodak?
I have a Kodak "official" gray card and it seems a lot darker compared to yours. The Kodak seems like when you fill a photoshop layer with 50% gray. Greetings from Brazil
How gray is grey?
Ansel Adams says 18% reflective held at a 45 degree angle to the lightsource.
Industry ISO standards say 12% reflective (I just had my exposure meter calibrated)
Middle grey on a digital file is 127,127,127 for an RGB file or 50,0,0 for LAB colorspace.
Kodak cards are only good for exposure reading not color balance. I have two from the same pack and they are slightly different.
Gray for white balance needs to be neutral under all lighting conditions.
Most injet papers sold have optical brighteners in them (OBA) which can give a purplish caste to the color. Wedding dresses have the same problem, they turn purple in the shadows outside or under UV light. This will give a warming correction factor to the image. You can buy non-neutral color balance cards to simulate the use of warming-cooling filters.
If you want an inexpensive grey card, buy a tube of artist acrylic paint. Look on the label for the color information of a N5 or L=50, a=0, b=0. Paint onto most any surface (cracker box, paper, your assistant's hand).
@ Michael Very informative.
@ Michael
Very informative. Thanks for the info!
I don't think the gray
I don't think the gray card must be neutral in every lighting condition. If that were the case you wouldn't be able to correct anything.
Jeroen
Homemade gray cards and Optical Brighteners
You have to keep in mind that when making gray cards, or anything you're going to use to set a white balance that it has to have a unifrom color response in all lights. In short, you can't use paper with OBA's in them as they'll be bluer than neutral under UV light. Not so important for setting an exposure, but really important for making a white balance adjustment as show here.
I did a test some time ago on using white paper to set white balances where I cam up with white balance errors of up to 1000K towoards blue with papers that use OBAs in environemnts where there's a significant UV component (like outside under the sun).
DIY White Balance
There are too many variables to consider when making your own grey card. Aside from the paper whiteners mentioned above, you have to consider the pigments used in your ink; toner; or plastic, and how they reflect light. There could easily be a spike in one of your color channels using one the above methods.
I used a Kodak 18% grety card when I first learned about digital photography. It's great for exposure, and I still have it, but all of my shots came out with a slight green tint. I use a WhiBal and a Colorchecker Passport now, but if you want a good DIY for white balance, get a coffee filter (white, not natural) and use it like an Expodisc.
Graycard
I made gray card from free natural gray color sample card for color mixing. I found it local DIY store. Like this : http://homeimprovementstip.com/kwal-paint-color-chart.html
Careful of reflections
Hi. Just be careful not to let reflected colour distort your reading. The surface of a Mac Book Pro is more reflective than most colour balance cards. Even a coloured desktop image (which you shouldn't have if you edit photos) could throw the reading off. Just a thought.
Or just shoot RAW? I mean,
Or just shoot RAW? I mean, trying to hold a piece of paper in front of you while holding a full frame camera, with my 24-70 is pretty damn heavy so I shake a lot. Adjusting in PS/Aperture is so much easier.
What about doing the card in CMYK color?
If you take a photo as reference, you are using RGB color. The printer will convert it to CMYK color. Then, you can lose de fidelity of the color in the gray card. Maybe, a way to make it more accurate is doing it in CMYK color. But how?
Maybe the differences the people are having in their cards is due to the problem CMYKxRGB
Argentinian pesos
Ohhh sadly the only value for our currency is to be used as a gray card sample image.
I need to start doing this..
I need to start doing this.. I do it the hard way, one image at a time!.. time consuming!!
.. first things first.. better buy an 18% gray card :-)
Good article. Since I am
Good article.
Since I am already taking a photo of a grey card, I usually use that picture to set a custom white balance in camera. Takes the hassle out of post production.
Middle Grey is 127,127,127 or
Middle Grey is 127,127,127 or H=0, S=0, B=50. How do I know this? I created a photoshop file on an 8x10 canvas had it printed at my local camera store on matte paper and then compared the Reflective and Incident meter reading usinga Sekonic 758-DR and found that the Inicdent and Reflecitive Metered within a 1/10th of a stop.
Bottom line 127, 127, 127. You could do this with a 4x6 and have it printed at any drug store for less than a $1.
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