How to make a "home-made" grey card?

Hello,

Has anyone here tried to make a home-made grey card? We know a grey card is

useful for colour balance and exposure adjustments, within the context of a

photoshop workflow.

I am thinking of printing grey with a laser printer since we know the "black"

on a laser printer is truly neutral black (carbon). But how do we go about

creating a grey pattern that is 18% or thereabout? Now we know that a laser

printer will print grey as a half-tone pattern of black dots. This patch of

tiny black dots will come out as a grey patch on the camera because the sensor

or film will probably not be able to resolve the tiny black dots.

Is my reasoning flawed in any way? Will this work as a grey card like

a "real" grey card?

The inside of my camera bags are 18% grey as most are. your best bet is to meter off that or just buy a card from your local camera shop for a couple bucks and save your self the time, and have the piece of mind knowing that it is a "real" grey card.

Craig Morris

I keep an 18% grey "Spudz" microfiber in my camera bag. In addition to metering, it's also useful for cleaning your lenses. It may vary slightly from a expensive 18% grey target, but when I've metered off of it, I don't think I've ever adjusted the exposure in import unless the light changed on me.

steve

In many graphics applications you can fill a block with a desired percentage of gray. Enter 18%, or choose 20% it'll be close enough to get started.

The inside covers of the National Geographic Field Guides to Photography are a convenient 18% gray.

You should be able to find a real gray card for a couple of bucks. It's almost more trouble to make one.

<Chas>

Some of the posts in this thread are ignoring the characteristic of the gray card for white balance. If you want to use a gray card as a reference for white balance, it is critical that the gray card have absolutely equal amounts of all colors - neutral, in other words.

For purposes of exposure measurements alone, the color of the "gray" card is not really critical, but the reflectivity can be problematic. Look at a Kodak gray card. It is a "flat" surface, not shiny in any way. That is important to avoid reflecting light towards the meter in the way that a mirror would.

The additional problem, other than reflectivity characteristics, with making your own gray card for use as a white balance reference is the unknown color of the paper itself and/or the unknown color of the ink or toner.

In my opinion, it is better to spend a few bucks and purchase a real standard gray card to use as a white balance reference.

A handheld meter that can do incident light readings (using the white transluscent dome to collect the light) is far easier to use than a gray card for exposure control.

Nope.

If!

Your laser printer has' embedded, one of those wonderful codes, printed as dots, in yellow, on every copy. In order to combat forgery.

Believe it or not.

Yeah...as some have mentioned it will be used mainly for colour balance adjustment, ie, with a dropper click in PS to achieve correct balance. That's why, being absolutely neutral is really important.

Well, I guess I am better off buying one.

Thanks to all above for your generous contribution!

1.) It is only useful for color balance if it is truly spectrally neutral. Which means thayt it

actual reflects equal amounts of red, green and blue light under a wide variety of light

sources.

2.) It is only useful for exposurre adjustments if you actually know that its reflectance value is

calibrated to a known standard like 18%

It should work but only as an 'approxive' grey card for the reasons already mentionned.

Still, if you want to proceed, pick a thick paper as matte as possible (maybe a photo inkjet matte) and test various light conditions with also a 'real' (official) grey card. You will probably have to print other ones to get closer readings unless the spread is different in various conditions indicating failure.

Some camera bags are 'grey card' color. They are not too bad when light is not too direct (reflection)

> Yeah...as some have mentioned it will be used mainly for colour balance adjustment, ie, with a dropper click in PS to achieve correct balance. That's why, being absolutely neutral is really important.

If it's just for colour balance there's no need to print anything on your piece of white paper at all! Photoshop can adjust colour balance from a white point. You'd only need it to be 18% grey if you were metering reflected light readings.

Matt.

First.

?Why do you think the gray of your printer is neutral? It seems to your gaze but you know we adjust the neutral to the "lost neutral thing" you can see in that exact moment.

Second ?How to get a 18%? Well theorycally filla image with a r=g=b=116 value. That is a 18% medium gray. If you have a good connfiguration of your color management system, it works.

BUT:

sincerely, it is easeier: Take what ever you want wich is gray, borrow a medium gray card and read the difference in stops beetween the gray 18% and the gray you have selected. Use always that "(non medium)gray card" with a "corection" of the difference value you read.