I'll tell you what I think duotones, etc. are. When printing B&W (on a press, like with a magazine), there is only a limited dynamic range you can get using one "black" ink and different size dots. So for real high quality results, particularly in "art" coffee table books, they use a couple different inks. As an example, think "black" and "light gray". By making the dots with different shades of ink, (on good glossy paper), they could get better dynamic range. More inks cost more time/money; so there were two tone flavors, three tone, and four tone, depending on desired quality and costs. Now, if the inks are not just pure grays but have some color, the B&W image can also be given a warm or cold "tone" to it. Much like the results in the B&W darkroom using chemical toners, selenium, sepia, gold, blue, etc. The results (with both actually) gives a "deeper" looking image than just by coloring or shifting the color balance in Photoshop. This is because, (very slightly) the image colors shift a little bit between the shadows and highlights. [With B&W coffee table books they actually used funky ink colors to get the best results. The results can be simulated with full color Yellow, Megenta, Cyan, Black dyes, which is usually how a B&W picture is printed (on a press) today.] Since Photoshop is used for production pre-press stuff, it has the capabilities to convert grayscale to duotones, tritones, or quadtones. They were never really meant for CRT screens, but they look pretty cool on a CRT, so why not? Now, inkjet printers use CYMK dyes, so whatever software converts the bits to splashes of ink is really doing a quadtone. However, for creative reasons, some folks like to play with the duotone settings in PShop. [However, there is an extra step, but don't worry about it: grayscale->duotone->RGB->printer. They are actually sending a RGB image to the printer driver.] Now, inkjet printers with standard CYMK dyes work pretty good when printing a B&W print. But not perfectly. So some company, (in Britain?), supplies different funky colored dyes to try to improve the results. [Here, its grayscale->duotone->printer using funky ink. This also needs special driver software.] They also make some claims about archieval stability. They invented a Marketing name for this, piezo-something, to make it sound impressive, but quite a few ink jets use piezoelectric cartridges to splash the ink anyway, (others boil it). Now, Epson gets real bothered by anyone putting different ink in their machines, (can you guess why?). So folks also offer conversion kits. Do you need this? I think you'd like working with the old chemical toners in your B&W darkroom. They are pretty toxic so be very careful. If you do PShop stuff for viewing on a CRT screen, just doing the duotone conversions is fun. Also, by having some control over the image tone you can maybe hide inadequacies (if any) in ink jet printers. The real use for the funky inks is if you want to print very high quality B&W on an inkjet. You also sort of need to know this stuff if you are working with press people reproducing your work, just so they don't snow you. Hope this helps. It sounded good to me anyway as I was making it up ;-) I think its basically correct, but if someone can add details, or has had actual experience with the products out of Britain, I'd like to know more.