Sequence viewing > Index - Alternative Photo Emulsions - Resource - © Lloyd Godman

Alternative Photographic Processes - (Hand made photographic -emulsions and processes)

Exposure tests - Step Wedge


Rather than use an image to carry out a series of tests, a tonal step wedge can be used to establish the correct exposure for the combination of paper, emulsion etc.

Creating a Step wedge

There are differnt ways of doing this

Method 1

Open a new file in Photoshop

with dimensions of 3000 PPI x 400 and a resolution of 360


1 Select the image - Control A

2 Select the gradient tool

3 Make sure the colours selected are Black and white

Once the image is selected and active then use the gradient tool. Move the mouse from the exact point of one end to the other - you should have a graduated tonal scale.

The select

Image - adjustments - Posterize

You can set the number of tonal levels in this case 10

In this case 20






Method 2

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.


Go to Image - Canvas size


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

Continue to paste IMAGE2 and fill it with the appropriate tone until you have a 10 tone scale from white to 50% Gray

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

Continue to paste IMAGE 2 - position the layer and fill with the appropriate tone
Once you have completed this you will have a 20 tone step wedge

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.


Although not necessary, you can expand the canvas size again and using the Text tool include this information along side the tone. Lets make the height 1200 and keep the anchor point in the centre.
Place the values above or below the tone
You can simply duplicate the text layer and retype he values for each tone



However this chart is a positive and for most of the proceses we need a negative


Using the rectangular marquee tool, select to tonal steps only
Select - Image - Adjustments - and then invert to turn the scale to a negative.

The completed step wedge can then be resized to the the size you need to do the tests and printed as a transparency - Agfa Copyjet film or




Want to learn more? - do a workshop or one on one with Lloyd Godman