1. Channel Mixer
The original Photoshop black and white conversion may have been the simple grayscale desaturation method, but it never looked very good. What quickly became the method of choice for discerning photographers was the Channel Mixer. This tool, found under the Image>Adjustments menu, is actually pretty simple for as powerful it is, and it works as well today as ever. The key is to click the Monochrome checkbox in the bottom of the preview window, so instantly you'll see that your photograph turns black and white. It's the next steps that give Channel Mixer its good name. Adjusting the Red, Green and Blue sliders allow you to alter the sensitivity to those particular colors in the finished grayscale image. In layman's terms, that means dragging the red slider down will darken red things—like lips and ruddy cheeks and red roses. Drag that slider too high and you can create an almost infrared appearance, where the red values turn practically white.
However you adjust the individual sliders, you may notice that keeping a combined value of approximately 100 will work the best, without dramatically changing the overall exposure of the image. The "Constant" slider at the bottom of the panel also offers wholesale exposure adjustment, most useful to compensate for changes that occur in the appearance of the exposure when it's converted to black and white.
I think what makes this approach so appealing to old-school photographers is that it works basically the same way as using filters with black and white film. Put a red filter on the lens to allow red light through and in turn you'll value red light more importantly in the finished image. Makes sense, right? There are even presets found at the top of the window which mimic those original black and white film filters. The downside of the channel mixer, of course, is that there are only three sliders, so this method doesn't offer the same level of refinements available with some other approaches. Of course, depending on how you look at it that could also be considered a benefit: it's easy to use. For more fine control with color slider conversions via Photoshop, look to the next option.
2. Black and White Adjustment
The Black and White adjustment is found not far from the Channel Mixer in the Image>Adjustments menu. This filter, though, offers six sliders—the primary colors of Red, Green and Blue, as well as their complementary hues of Cyan, Magenta and Yellow. With twice the sliders you can be exponentially more precise with your adjustments. This may be a bit overwhelming for a new user of Photoshop for b/w conversions—and for some things I still prefer fewer slider options—but for someone who's looking to take their black and white conversions to the next level, Photoshop's Black and White adjustment offers plenty of control. It, too, has a dropdown menu of preset options—a number of them in fact—that also mimic the old-school "black and white film with filter" approach.
The Black and White adjustment tool also offers additional controls that are specifically suited to fine-tuning grayscale images via toning. The Tint checkbox toward the bottom of the window allows users to select a tone to add to the photo—like sepia brown, for instance—and the Hue and Saturation sliders allow for the subtle adjustment of the tone on both counts. Much like darkroom printers eventually graduate from basic black and white to prints with the addition of toning, digital developers may prefer these added tonal controls in the Black and White adjustment window. Ultimately it's where I graduated to after I really got the hang of Channel Mixer, but I still use both tools depending on what a photo needs.
As for drawbacks to this approach, I'd say they're found in the presets. Sure, there are options available, but they're fairly limited when compared to the wealth of presets available in conversion-specific plug-ins, and even those available for download or custom creation in Lightroom.
strong>3. Lightroom Black and White Conversion
For users who are comfortable making these slider-based adjustments, Adobe has built in the same sort of controls into Lightroom's Develop Module. Found under the Basic heading, the Treatment section of the Develop module is where you can make a one-click conversion to black and white. This is perfectly acceptable as an instant fix, one that can be batch applied across a number of photographs with the equally simple Synchronize Settings command (Command-Shift-S, for those of you so inclined). This synchronization is even more powerful when applied later, after some custom adjustments have been applied to an image. For this, the one-click black and white approach falls a bit short.
Scroll down farther in the Develop module and you'll see the HSL/Color/B&W heading. This panel is where the control is found for your black and white conversion. The Black and White Mix is active by default when you've clicked the one-click conversion up above. If you're still looking at a color image at this point, however, simply click on B&W in this panel and the conversion will happen. Lightroom analyzes the image and applies an automatic mix in hopes of giving you a perfect black and white conversion. Good as it may be, though, it can always be better when fine-tuned with a human touch. Simply adjust the sliders here, as you would in the previous two Photoshop methods. These filters include a full eight colors for even more fine tuning control.
4. NIK Silver Efex Pro 2
If you're serious about making black and white conversions, or if you plan to make black and white a major part of your process, or maybe you just want to pull out all the stops and see what options are available in the world of digital black and white, you sound like the perfect customer for investigating options outside of Photoshop. Dedicated black and white conversion software offers more customizable control, in a ready-for-black-and-white package that no do-it-yourself approach can quite match. That's not to say software like NIK Silver Efex Pro 2 isn't totally customizable. On the contrary; it probably offers as much black and white control as any other option, but it's presented in a framework that offers good suggestions on where to start. The popular software is now available in the Nik Collection by Google, which retails for $149. I'm categorizing it as a single conversion method, but really what makes Nik Silver Efex Pro 2 so useful is that it provides many different controls to produce black and white conversions in a variety of ways—making it easy to choose a conversion method that's instantly appropriate for your subject.
5. The Gorman Method
Mostly I like it because it produces a look that's slightly different than any of the above approaches, and it's perfect for portraits. Plus, it's also totally customizable in a variety of ways, making it easy to fine-tune the conversion with every image. Rather than recount the approach here—which is based on a conversion to LAB color mode for the selection of the Lightness channel—and steal the man's thunder, I'll point you directly to his web site where he's generously published a PDF tutorial to share his method with the countless photographers who are continually looking for a better way to black and white. Download Gorman's guide at http://www.gormanphotography.com/Duotone.pdf.