Duotones, tritones, and quadtones use spot color inks and multiple passes on a printer. They are expensive to produce because of the separate plates and press washes. Photoshop has a duotone mode. Printing these images on an inkjet printer results in a pseudo-duotone. These can be very lovely images and nearly indistinguishable from a true duo/tri/quadtone.
If all you want to do is produce a toned B&W print, there is no need to use Photoshop to convert your image to Duotone mode. You can use the TLR B&W Split Toning Lightroom Presets instead.
Below is a sample photograph before and after application of the Burgundy Gold preset.
This collection of Lightroom presets is designed to simulate the same effect obtained with the TLR B&W Toning actions for Photoshop.
The presets for basic tones apply a moderate color tone to the phortograph. You can choose from Blue, Brown, Burgundy, Cyan, Green, magenta, Mauve, Purple, Red, or Yellow.
The presets for sepia tones apply a light to moderate sepia tone to the image.
The presets for color casts apply a light tone to the image. The tones are designed to impose a slight cast to grayscale images or remove a slight cast by applying a neutral gray tone. You can choose from Gray Green, Gray Mauve, Cooler Gray, Neutral Gray, or Warmer Gray.
The presets for the traditional tones apply a moderate tone to the image. The tones are designed to simulate traditional toning processes from a chemical darkroom. The available tones include Cyanotype, Gold, Palladium, Platinum, Platinum Palladium, Selenium, Selenium, Selenium Brown, and Silver Gelatin.
The presets for the traditional tones apply a moderate tone to the image. Instead of applying a single tone, a combination of tones are applied to the image. The multi-tone actions include Aqua Gold and Burgundy Gold.
You can then adjust the settings to your liking, something impossible to do with a traditional filter and film photography.