If you photograph for a living, shoot products, do large events, or events/settings that involve differing lighting conditions, you know the importance of color balance cards. For example, I shoot bodybuilding shows and private photo sessions. The light literally changes every few minutes as the stage light changes (usually with every category change, when groups change, and sometimes from contestant to contestant!) Combined with the wide variety of skin colors, air-brushed tans and bottle tans - plus the combinations of those - it's next to impossible to get accurate colors. Since I shoot from many rows back - or the balcony - I need a BIG card. Plus when I do private shoots, I'll often need the client to hold the card for a few shots. The coloring transfers to the card and gets everywhere. Plus it's destructive to many surfaces and paints. Seriously - I had one client grab my expensive gray card and leave a thumb-print that was etched into the surface by the time I noticed it.
Plus I need to leave large cards on the stage, out of the way so I can batch color process in Lightroom. Many times these cards get stepped on or tossed by the stage crew - so they need to be cheap. I can go through several in one show. So I had to come up with a cheap alternative.
The solution - card stock, satin black paint and gray paint. For the gray paint I actually took my color card to Home Depot and had them color sample it. The result - neutral gray paint. You can get a $3 sample can mixed, or a $10 quart. A little goes a long way.
Step 1: Foam Core - Cut to Size
I have plenty of scrap foam core lying around. I cut this to size depending on the final size of the cards I need. I combine black, white and gray on each card. Foam core works best. Card stock warps and ripples, and corrugated plastic or cardboard casts shadows. Any WHITE foam core works.
I cut several cards from one sheet.
Step 2: Mask and Paint the Black
Mask the foam core, leaving what will be the the black portion exposed. My preference is that this is about 20% of the card. You need to mask the entire card except for the part you'll paint. You want ZERO overspray.
Use satin or flat black spray paint. Give it a nice, even - heavy coat. One coat will do it. Remove the masking tape and overspray cover (I used cardboard) after a couple of minutes. Just don't touch the paint.
Step 3: Mask and Paint the Gray
Next paint the gray area - the black is still drying, but if you're careful it's not an issue and saves a lot of time. I use a foam brush to avoid brush marks. Again, a single heavy coat will do it. The unpainted white in the middle remains unpainted. Remove the masking as soon as you're done painting.
Having the white in the middle is a big time saver - you can paint the two "colors" almost immediately. If you want the "colors" to touch, you'll need to wait for the first one to dry completely - usually 24 hours.
Step 4: Optional: Make Some Big Gray Cards
Since the brush is already wet, I paint some more scrap foam-core. I'll eventually need it anyway.
Step 5: Cut Out Cards
I make these a couple of times a year - usually white in the middle, sometimes gray. Again - personal preference. Just take a ruler and utility knife and cut the cards out. Obviously you can make different sizes. The ones I made hare are about 20" long. The "optional" gray cards I cut to 12" squares so I can "see" them from 150 feet away.
Each card costs under a buck so it's no biggie if you lose them or they get ruined!