Converting a Color Photo to Black and White with Photoshop
Once upon a time you had to purchase black & white film and have the film processed differently if you wanted to see your photos in black & white instead of color. Of course, it's not that long ago that all photography was done exclusively in black & white. These days it's quite different, though. We use digital cameras that record photographs as small pieces of computer memory that can be accessed and played with. But how do we take the color info that our cameras record and turn that into a good representation of a classic black & white photograph? Figure 19.1 shows the result of a color photograph that has been converted to black & white in Photoshop CS2.
NOTE: This Photoshop lesson was created using Adobe Photoshop CS2, but the same results can be achieved in just about any version of Photoshop.
There are a few methods that can be used to convert color digital photographs to black & white. The first two are very simple and the results are good, but if you are a little more picky about how your photographs will be seen, then you'll want to opt for the third option I'll demonstrate.
By simply changing the mode (choose Image, Mode, Grayscale) you can quickly and easily change any color photo to black & white. When you choose the Grayscale mode you will be presented with a dialog box that warns you that all color info will be discarded. Clicking OK will convert the image (see figure 19.2) to Grayscale.
Note that you will be able to use some, but certainly not all of the filters that you'd have access to with a full-color image. You can, of course, convert the image back to RGB. This won't magically re-color the image though. You discarded the color info, right. Hmmm... maybe the easy solution isn't the best idea.
NOTE: Changing the color mode has no affect on the bit-depth of your photograph. That is, if the image is 16-bit color, it will become 16-bit grayscale.
TIP: Changing the color mode of an image is a destructive process! You might be more comfortable working on a duplicate of your photograph. To duplicate any open image in Photoshop, simply choose Image, Duplicate. You can name the copy or simply leave the default setting.
Another fairly easy method involves tossing out the color info yourself, but leaving the color mode the same (most likely RGB). To use this method you can choose Image, Adjustments, Desaturate. This method doesn't warn you that the color info is being discarded, but the results are pretty much the same, except that the color mode is preserved. Figure 19.3 shows my color photo after Photoshop has "desaturated" it.
Adobe Photoshop has a proprietary mode called Lab (for Lightness plus a, and b color channels). The important part of this is that we can use the Lightness channel from that mode as a black & white representation of the photograph. Pretty cool stuff, quite easy and it yields quite good results in many cases. Here's how...
With your photograph open in Photoshop, convert it to Lab mode by choosing Image, Mode, Lab Color. Note that, as stated in the TIP above, you may wish to work on a duplicate of your photograph.
With the image converted, open the Channels palette (it's usually tucked in with the Layers palette, and you can open it by choosing Window, Channels) and click the Lightness channel. You should see your image turn to black & white.
Choose Select, All to select the Lightness channel's info, and then choose Edit, Copy to copy the channel to the clipboard.
With the channel selected and copied, click the Lab channel in the Channels palette to turn on all of the channels. Go back to the Layers palette by selecting its tab or by choosing WIndow, Layers.
Choose Edit, Paste to paste the Lightness channel into the image. This channel actually yields pretty good black & white results. You can see my effort in figure 19.4.
This method is the most involved, but it also offers the biggest rewards. The channel mixer has been around in Adobe Photoshop almost forever, but few people seem to know of its existance or how it works. To see the magic first-hand, open a color photograph that you'd like to convert to black & white.
With your image open, choose Layer, New Adjustment Layer, Channel Mixer... Doing so will do a couple of things. It will, of course, open up the Channel Mixer dialog box, which we'll get to in a moment. It will also make any of your changes on an adjustment layer. What this means is that this method is non-destructive and completely editable, even after saving the image (as a .psd file, of course). This is great! It means that if we decide to get back the color, or even re-adjust the black & white settings, all we would need to do is discard the Channel Mixer adjustment layer that we created, or open it back up and adjust the values. Sweet! I'll show you, at the end of this tutorial, how to re-edit the values.
With your image open and the Channel Mixer dialog box open (see figure 19.5) place a check mark in the Monochrome check box and make sure that Preview is on.
When you first open the dialog box, the setting for Red will be 100% and Green will be set to 0 as will Blue. You can play with the settings in many ways, I've drawn from the Red and Green quite heavily and evenly, for example, but left the Blue channel with very little input on the final black & white image. You may note that I've used settings that add up to more than 100%, this is fine, and in this case it simply makes the image a little lighter (I tend to underexpose when shooting digital photographs). You can also brighten or darken the image by playing with the "Constant" value.
You can try using one channel or another by setting that particular channel to 100% and leaving the other two at 0. In fact this is a good way to see what the different channels hold in terms of the info that makes up your image. You'll notice, for example, that the blue channel (set Blue to 100% and Red and Green to 0) seems to be the "noisiest".
As you play with the various channel settings, you'll see that you can actually enhance the image. For example, it's possible to darken areas, such as a persons lips, by choosing different settings for the three channels.
The reason I favor this method over the others is that it is so flexible and so powerful. By changing the values of the different channels you can really make a difference in the final black & white image. Some of the power comes from being able to re-visit these settings at a later date. To do so, simply double-click the leftmost icon in the adjustment layer that you created (see figure 19.6). Doing so will bring up the Channel Mixer Dialog box with the same settings you chose preserved and ready for more playing around :)
Figure 19.7 shows my final image.
That's it.... Be sure to check out some of our other Photoshop tutorials. Our next tutorial, for example, shows you how to make advanced selections using quick mask techniques...
Everyone loves a quickie, especially if the quickies are free Quick Tip Videos for Photoshop. Our "Quickies" are short, web-based videos (approx. 2 minutes, or less) that highlight some neat trick or time-saving tip for Adobe Photoshop. Go ahead and check them out... you know you want to :)