The grey card you can buy is a known calibrated reference.  There's not
much point in printing your own unless your printer and computer have
already been calibrated with a bunch of grey and other cards and
equipment.  I suggest you get yourself an 18% grey hat.  Then you can just
put your hat
<https://petapixel.com/2015/11/19/this-cap-doubles-as-a-gray-card-for-light-metering/>
on the things you're photographing and get the exposure right, take the hat
off (or not) and take your picture.

On Tue, Feb 21, 2017 at 9:15 PM, Michael <bmike1@gmail.com> wrote:

> Well, for my photography needs it seems I need a gray car. They cost what?
> Well, I guess I'll print my own. So I open GIMP and they want an HTML code.
> Anyone know what the code is for 18% gray? If 18% is right in the middle of
> the shades of gray I found one page that says the code is
> 808080
> and according to the same page it is made up of equal part RGB
> *W3C Color Name:* Grey
> *RGB:* 128, 128, 128
> *HSL:* 0.00, 0.00, 0.50
>
> --
> :-)~MIKE~(-:
>
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