Open a new file in photoshop 600 Pixels wide x 300 Pixels high - 72dpi

Create another new file - lets call this IMAGE 2 -

300 x 300 Pixels and fill the area with 10% gray from the swatches using the paint bucket tool - select the total area (control A)

and copy ( control C) the file

and paste it ( Control V) into the first file you made - each time you paste the image it creates a new layer that allows you to move it etc independently of the other layers -

then move the pasted layer to the right - this should give two 300 x 300 squares one white the other 10% gray.

This allows the expansion of the canvas size while leaving existing information untouched

change the width to 3000

and set the anchor point to the centre left then click OK

this will give a canvas large enough to past in the remaining gray tones on the top line of the wedge to create 10 tonal steps.

Continue to paste in the the square from IMAGE 2 and using the eye dropper select the next tone - 15% - 20% etc on the scale and fill the area with the paint bucket tool -

Use the move tool to position the square next to the adjacent one

Go to Image - Canvas size again

and alter the height to 600

make sure you select the top centre anchor point. This will expand the canvas to allow the lower row of tones to be inserted

Photoshop will give you a series of numbers or values that relate to each tone.

When we move the eye dropper 1 & 2 over a tone it will show a % gray

in this case 35% gray - 3.

From widow we can open the info box which will give a Cyan Magenta Yellow - 5 and K - 4 - or density value for the tone you are choosing.