The Curves adjustment layer provides a very sophisticated method for modifying the contrast of an image, but that's not all that you can do with Curves. Here's how to duplicate the colour toning of a reference image so that you can use it to tone other black & white pictures.

I'm going to base my curve on the toning of this albumen print, made by the Victorian photography pioneer Eadweard Muybridge in 1880:

Step 1: Open your reference image in Photoshop, then copy the original image to a new layer. Name this image BW. Step 2: Desaturate the BW layer (Image > Adjustments > Desaturate). Step 3: Choose an area in your reference image that contains shadows, midtones and highlights. I picked the area marked in red in the following screenshot. Zoom in very close to your chosen area, so that you can see individual pixels.

Step 4: Select the Color Sampler Tool from the toolbox - it's in the same group as the EyeDropper Tool. Use this tool to select 3 pixels - a shadow, a midtone and a highlight. Each selected pixel will be numbered and highlighted when you've marked them, as in the image to the right: Step 5: Make the Info palette active (it's in the same group as the Navigator and Histogram palettes). It will look something like the example on the left. The lower part of the palette shows the Red, Green and Blue values for each of the numbered pixels that you marked with the Color Sampler. Write down the values for each pixel.

Step 6: In the Layers palette, hide the BW layer to make the original image visible. Note that the values for the three marked pixels will change to show their corresponding values in the original image:    Write these values next to their black & white versions. You should now have a table looking something like this: Marker Channel BW Original 1 (Shadow) Red 22 38   Green 22 15   Blue 22 7 2 (Midtone) Red 119 157   Green 119 131   Blue 119 82 3 (Highlight) Red 224 252   Green 224 227   Blue 224 196

Step 7: You can now create your curve. Select Layer > New Adjustment Layer > Curves from the main menu. In the Curves dialog box, select Red from the Channel drop-down box. Click on the line near the top to add a point, but don't drag the curve. Now, in the Input box, type the RED HIGHLIGHT value from the BW layer's column in your table (in this case 224). In the Output box, type the corresponding value from the original layer's column (in this case 252). Click the line in the middle, then enter the RED MIDTONE values from your table into the Input and Output boxes as described above. Click the line near the bottom, then enter the RED SHADOW values from your table into the Input and Output boxes. Your dialog box will now look something like the image opposite.

Step 8: Select Green from the Channel drop-down box and repeat the above process using the GREEN values from your table. Select Blue from the Channel drop-down box and do the same for the BLUE values. Now your custom toning curve is complete. Click the Save button, give it a suitable name (I called mine Muybridge.acv) and save it in your Presets\Curves folder. You can now close your reference image. Step 9: To use your new custom curve, open up a new image in Photoshop. Here's mine: Use your preferred method to convert the image to black & white - I used a Channel Mixer layer, but you can use the desaturate function if you prefer that method. Select Layer > New Adjustment Layer > Curves from the menu. In the dialog box, click the Load... button and navigate to where you saved your custom curve. Select it and click Load. The toning is applied to the current image. Here's the result: Of course, since it's an adjustment layer, you can always tweak the curve to better suit the image once you've loaded it. And thats it - hope you've had fun & learned something useful!

- Tutorial written by Tamlin

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