Black and White from Colour Images – Part 2 – Digital Photography Tip of the Week

Last week I began my discussion of black and white digital photography. This week I will further that discussion by talking about the first two methods of converting your digital photographs to black and white, or more specifically, monochrome. For the sake of simplicity, I will use black and white in my text, but even traditional wet darkroom methods had ways of introducing a color tint or tone into an image, so monochrome is a better descriptor for the final images.

The two methods of black and white conversion I will discuss this week are desaturating the image and converting to grayscale.

Saturation refers to the intensity of the colour in your photograph. An image with bright colors have high saturation while image with pastel colors have low saturation. If you remove all the colour saturation in the image, you end up with a photo that looks like a black and white image.

To desaturate an image in Adobe Photoshop Elements 4.0 , from the menu choose Enhance => Adjust Color => Adjust Hue/Saturation (CTRL-U). Then, simply drag the saturation slider all the way to the left. The same shortcut works in Adobe Photoshop CS2 , but the menu location is different. In CS2, use Image => Adjustments => Hue/Saturation. However, in order to preserve image data, I prefer to create an adjustment layer using Layer => New Adjustment Layer => Hue Saturation. Again, simply slide the Saturation slider to the left. Using desaturation to remove the colour from a photograph affects the red, green and blue channels equally.

Converting to grayscale is a very simple process, but it changes the data in your image. If you are converting to grayscale, you probably don’t need the color data anyway. When converting to grayscale, Photoshop places more emphasis on some channels than others, in the proportions of 30% Red, 59% Green and 11% Blue. This provides a more natural conversion of your photograph and more closely resembles what we expect to see.

dptotw-bwexamples.gif

The example above shows four colors in the first row, red, green, blue and yellow. All four have the same brightness (or luminance). The second row is the same four colors, only this time they have been desaturated. Because they are of the same brightness, once desaturated, they look the same. Finally, the third row is the same colors but this time they have been converted to grayscale. As you can see, There is an obvious difference.How do you know when to use which method. Using the desaturate creates a very flat image that is rarely, if ever, very impressive. Converting to grayscale is the obvious better choice. It should yield acceptable results, most of the time. Is the best choice? If you are using Adobe Photoshop Elements , it is. If you are using another program, such as Microsoft Digital Image Suite or Adobe Photoshop CS2 , there are still better ways.

Next week I will talk about using Channel Mixer to convert you colour photographs to black and white masterpieces.

The digital photography tip of the week is written by the PCIN Assistant Editor, Chris Empey. Chris is a long time photographer and is currently the President of the Niagara Falls Camera Club. You can see more of his photography at his Photo of the Day website. If you have a tip to send Chris, or a question about digital photography he can address in the newsletter, send it to chris@pcin.net.

Comments 2

  • Dear Chris,

    You did not say how to convert to a greyscale image but looking in the help area it stated to click on “Enhance>Adjust Color>Remove Color” to convert to greyscale in Photoshop Elements II.

    Having created an image using the “Desaturated” method and also the “Greyscale” method, and saving each, I cannot see any difference at all. In fact both files turned out the same size also.

    Am I doing something wrong?

    Thanks,

    Cameron

  • Hello Cameron,

    It sounds as though the remove color command in PS Elements II is desaturating the image, not converting it to grayscale. I am sorry but I do not have a copy of Elements II to test with however, if you use the image from the article of the three squares, and try both methods, and compare the change in the top row to the two examples I provided, that should provide you answer.

    In the new versions of Elements/CS2, you can convert the image to grayscale using the Image=>Mode=>Grayscale command.

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