I’ll lend a hand here. And I apologize in advance for length, but do bear with me, I promise it’s worth it.
The industry standard for imaging is Photoshop; my comments apply readily to others (Paint Shop Pro, PS Elements), but for specific directions I’ll reference PS. And I must disclaim: There are about a thousand ways (and counting) to perform any one action in PS. Rarely is there ONE best way.
Don’t bother filtering the camera. Straight B&W filters on digicams throw away data unnecessarily. Film cameras benefit to some degree, but primarily because of the superior grain characteristics of B&W film, not artistic intent.
SO. Capture your images in color. Convert them to black and white. But how?
This is where PS comes in. There are four ways I recall offhand: A) converting directly to Grayscale color mode, throwing away color data, B) Dropping the ‘Saturation’ slider in the Hue/Saturation adjustment box to -100, C) Converting to LAB color mode and keeping only the luminosity channel, and D) Creating an ‘Channel Mixer’ adjustment layer on the original color image.
I’ll expand a bit before I continue.
Unless you’re capturing in RAW (as opposed to TIFF, JPG), your digicam images default to 24-bit RGB color. 8 bits, or 2^8=256 colors, per Red, Green, and Blue channel. Because we see green better, and because camera CCDs (devices that record color information) are generally 1/2 green, 1/4 blue, and 1/4 red*, the green channel tends to hold more information than the red and blue.
*With one exception, digital CCDs don’t see true color. Each CCD element (a 3 MPixel camera would have 3 million) can detect only monochrome, so color filters are placed in front of them in the proportions I mention above. The camera then interpolates (estimates with sophisticated algorithms) 24-bit 3-channel color.
This is why you don’t want to use a B&W filter. Such a filter forces you to use the red, green, and blue channels in predefined proportions which almost certainly WON’T result in an optimal image. The first three methods I mentioned in PS do the same.
But the fourth…
Within PS, you can view and edit channels individually. The channel mixture allows you to choose how much of each channel you’d like to affect the image.
Brief tutorial on channel mixer
That’s the gist of the method. Keep this in mind:
"Just try and ensure that the combined total of the mix is roughly 100%
So, onward to another issue. Warmth!
Many grayscale prints appear warm because they’re not really grayscale. Nephorm mentioned Duotone. Duotone is a method to improve tonal range in a B&W. With few exceptions, printers have only solid black ink. An 8-bit grayscale image has 256 shades of gray. Obviously this presents a problem; how can I reproduce various shades of gray solely with black ink?
One method is dithering, or modifying the size, location, and density of ink drops to give the illusion of gradual tonal changes. All inkjet printers do this by default.
Duotone is another way. Or rather, an additional way. Instead of just black, duotone throws in a lighter second color (or a third or fourth, as in Tritone and Quadtone respectively) to add depth to shadows and smooth highlight transitions. I say color, but if the printer had grey ink, gray could just as easily be (and often is) the second hue. If you duotone with yellow and black, every color lighter than solid black would be yellow-gray. And light yellow-gray. And dark yellow-gray.
In other words, it’s a method to improve printing accuracy. Not necessarily an artistic instrument. But it just so happens that a touch of yellow suggests warmth, which is why you’ll rarely see green or blue as a second color.
Actually, ‘colorizing’ the image within the Hue/Saturation edit box has a nearly identical effect onscreen; Duotone merely ensures that your additional hue matches an easily-reproduced ink color.
And the last topic: Levels!
And curves, an advanced version of Levels. Even given the avalanche of text I’ve already written, an adequate explanation of the two is beyond the scope of this post. Thus I refer you here:
Apple’s excellent free video tutorial on Levels/Curves
BUT, I will give a quick overview of the most common use for them.
Say you have an image in which the subject is too dark. You took a picture of someone facing you, back to the sun without a fill flash, and your camera rendered them as a black outline with barely visible features. Like this.
Now, every imaging program has a Brightness/Contrast box. The problem with Brightness is that it changes every pixel uniformly. Your darkest shadow (RGB: 0) becomes light gray, your lightest colors (RGB 200+) become clipped when they reach RGB 255, and your friend is no more visible than before. So, in short, Brightness sucks.
Levels and curves allow you to edit the luminosity of any given RGB (or each channel individually) range independent of the others. So if your friend takes up RGB:20 to RGB:40, you could amplify that range and leave your shadows at 0 and your highlights at 255, and thus preserve the look of the picture.
That’s as much as I’ll burden you with today. Best of luck, and let me know if I’ve been obscure at any point.