For example, you might want to emphasise several selections of the green channel that uniquely highlight subtle detail, and you might also need the sky of the red channel to make the clouds really stand out. You can paint out/in or erase what you don't need in any channel and use the opacity tool and further image adjustment layers to properly mix the key elements and tonal values together before combining them all into the final image. Sound like a lot of trouble? Can be! But what are your best images worth?

Image-editing software techniques can really extend the traditional darkroom approach to B&W. But it's not a fast learning curve. It takes regular practice. Some time ago I processed a colour negative frame into black and white. I used colour data for separate areas from all three channels to get a solid tonal range in the grass and trees. I was able to usefully cut through the haze in the shot and draw out detail on a distant mountainside.

Click HERE to see colour version

The individual colour channels

Most of the grass was taken from the blue layer, the mountainside from the red and detail on the trunks from the red and green layers. I then spent quite some time fiddling about with the opacity of each element before I settled on the final combination. Before ordering an 18x12 print, I added a toned effect.

Masking techniques, like using mask overlays, will allow you to edit exact areas of the image while automatically protecting everything else. You can even paint an editable mask area in place. Masking allows for remarkably precise editing but, as with the image below, you may find that the general mask tools and the erasure tool can go a long way to leaving you with the separate elements in free layers that you can bring together and fine-tune as needed with the opacity feature and adjustment layers. Of course you can use masks in and from separate Channel Mixer adjusted layers and draw those portions together, but simply splitting the colour image into three pure channel data images and stacking them in layers is a straightforward and flexible method.

If this process is new to you, and your chosen software will allow you to split an image into colour channels, take a strong colour shot that you feel might look good in B&W - whatever that may mean! The visual combinations and elements within the image are important because the colour can't be relied on to promote the final print. Then start by separating the channels and stacking them in layers (simply copy and paste in P-P). You can further extend the creative possibilities by making good use of your software's merge modes.* Then take it from there and experiment to see what you can do with your images. This methodology is usually slower than the less thorough Channel Mixer approach, but the extended creative control is worth all of the extra effort.

It's most important to have complete control over the tonality of each channel and to be able to throw away any area of any channel that doesn't contribute to the final result you have in mind. There's fantastic potential here for quality B&W prints.

† Channels split from film scans may produce better results than DSLR images which incorporate in-camera colour interpolation.

* "On computers, colors have numeric values, and merge modes let you perform mathematical calculations with these color values. Merge modes combine a source and a base color in an image to produce a new color or effect, called a result color... merge modes [Add, Subtract, Multiply, Invert, Overlay, Color dodge, and so on] alter the way the colors of an object combine with the background behind the object or with underlying objects" (Corel). In fact, this is a bit misleading as colour doesn't need to be present in an image for effective merging results — all that's needed are different tonal values.