The Epson 9800, Epson 7800, and Epson 4800 printers (9600, 7600 also) do allow you to choose between using Photo Black or Matte Black. However, not only does it allow you to choose -- it basically forces to you choose because changing the inks later on will cost significantly you in ink, time, and resources. With this option in front of you, should you use Matte Black or Photo Black?
This is actually a very simply answer and we will explain it as simply as possible. The answer depends on your particular business. If you are a fine art printing company that will be primarily printing onto matte inkjet canvas and matte fine art papers, then you need to use matte black. When used on matte inkjet canvas or papers, the matte black is going to give you a much higher black density (called "Dmax", or black "pop"). The difference is significant. Even today you will find some printmakers naively using photo black inks and printing onto matte canvases or papers and selling them to artists as if they are "the best you can get". It is truly unbelievable. These people need to get with the times and either swap out the photo black cartridge or only print onto glossy substrates. The fine art printmaking industrty is still very fragmented rather than centralized and organized in a yellow-pages like fashion, so some businesses are going to be able to get away with this incompatibility for some time. Needless to say, this really is a losing strategy in the competitive lanscape. This is common knowledge to any self-respecting fine art printmaker, who has done enough due diligence to know that matte black ink should be used on matte substrates.
This doesn't mean the every single fine art printmaker must be using matte black ink. It's important to understand that if a fine art printmaker is printing onto a glossy inkjet canvas, he will want to use Photo Black ink instead. This is because the matte black ink is not micro-encapsulated and it will therefore not adhere well to glossy, luster, or semigloss coated papers or canvas. Glossy canvas, like glossy photo paper, is a glossy substrate and therefore photo black ink will also allow for the higher Dmax. This is why you will find many photo labs across the world using the Photo black ink cartridge -- they print on glossy substrates more often than not, and therefore need to have a printer using the Matte Black ink.
If the printmaker is going to then switch to printing on a matte fine art paper and he demands the highest quality standards, he will need to either switch out the photo black ink cartridge for the matte black, or have an additional printer set up with the photo black ink cartridge. Since the Epson printers are so inexpensive, most businesses these days simply keep an additional Epson 9800, Epson 7800, or Epson 4800 on hand with the opposite black ink cartridge.
Note that its the Photo Black ink that comes with your printer when you purchase it.Â If you want to use matte black right from the start, you need to request this cartridge.