Black & White Imagery

I spent a while this morning preparing for a lecture I'm giving next week to my high school's digital photo 1 class. We'll be talking about black and white conversion in Photoshop, and I thought it might be interesting to post my notes here as well.


Color exists in Photoshop in the Red/Green/Blue “RGB” colorspace. While not a color itself, RGB is our formula for mixing color. Think of RGB as the “bucket.” R, G and B are the paints.

  • Why not just capture in the camera’s B&W mode?
    • Less tonal control – if you capture n B&W you are letting the camera make important tone and color decisions for you.
    • No color data exists, once you capture in B&W, you are eliminating the color option, our goal with all things Photoshop is to practice non-destructive editing – a workflow that will let you step backward at any time should you so choose.
    • Most cameras simply desaturate the image when they capture in B&W.

  • Why is desaturation not the way to go?
    • When we desaturate an image (images -> adjustments -> desaturate) we are simply removing the color information from the image, what you end up with is an image that is 33% Red, 33% Green and 33% Blue.

  • What about converting to Grayscale Mode?
    • By going to Image -> mode -> Grayscale, you will achieve a similar result to desaturation. Before you do so, Photoshop will prompt you, “Do you want to discard the color information?” Right there this should tell you this is a bad idea, Photoshop is about exerting control, not giving it up.

  • How do we exert maximum control?
    • The first step toward total B&W control is to view out images in their separate RGB channels. To do this, click on the Channels palette. When the R/G/B Channels appear, selectively click on each one to view the color data independently.

    • Channel Mixer Layer
      • Click in the layers palette (the half black, half white circle)
      • When the Channels box pops up, click Monochrome.
      • Photoshop converts the image to B&W, giving you it’s default channel settings, 40% R, 40% Green and 20% Blue, but we can do better.
      • Again, it’s usually a good idea to first view each image at 100% in each channel to get an idea of the best parts of each channel. (Hint, for dramatic skies, try moving the Blue Channel to negative values.)
      • Advanced Move: Create each channel in its own layer, which will give you 3 layer masks so you can selectively paint each channel into the image.
      • As a general rule of thumb, your total values should be around 100%.
      • Use the constant slider sparingly, as it can result in dramatic brightness tonal changes (positive values will brighten your image and vice versa). I try and avoid using it all, preferring to make my lightness adjustments in a separate curves or levels layer.
    • Photoshop CS3 also has a new tool for B&W adjustments. It’s similar to the Channel Mixer tool, but has more specific color channel options and a “scrubby slider” for making adjustments. The scrubby slider will allow you to click and drag (left and right) directly on the image to affect the B&W color values.

  • Adding tone to B&W images
    • To add tone (warm or cool), to our images, we can create a separate Hue/Saturation layer on top of our B&W layer. When the dialogue box pops up, check the “colorize” box. Click and drag the Hue and Saturation sliders to add tone to the image – a little goes a long way.

  • Finalizing your images
    • After you have a B&W image that you are happy with, the next steps usually are to evaluate the contrast of that image and make any final adjustments. Usually this will mean a curves adjustment layer (for contrast) and a Shadow/Highlight adjustment Layer (to open any shadows that may have blocked up (completely black) and to try to recapture any highlights that have blown out (gone completely white).
      • When you create your curves layer, you will first want to change the blending mode of the layer to “Luminosity.” This means the layer will only affect the image in Light and Dark terms, and will not alter it’s saturation. If you do not make this change, darkening your image will result in increased saturation, and vice versa.
        • Keep in mind that viewing a photo, the eye naturally goes from light to dark, and sharp to blur.
      • In the vein of staying non-destructive, the Shadow/Highlight layer will first require you to duplicate your background layer (Cmd: + J), then convert it to a smart filter (Filters -> convert for Smart Filter). This will let you make further adjustments later should you so choose.