Create a banded gradient in Photoshop?

I`m trying to create a banded gradient with Photoshop, similar to the one pictured on this packaging:

Can I achieve this with a normal gradient in Photoshop or do I have to create this rectangle by rectangle?

Answer

It's probably easiest to create this by hand, or rectangle by rectangle. One way to somewhat recreate this is by going to Filter > Filter Gallery > Artistic > Cutout and playing with the settings in there. I got this, really quickly:

It's not the prettiest or most precise, but maybe that is because of the gradient I chose.

Another way is to change the color mode to Indexed (Image > Mode > Indexed Color) and then fiddle with those settings, but this still doesn't produce exactly what you're looking for.

That's why I think it's probably best to do it by hand. Maybe there is a method I don't know of yet, but these are the two I've seen used for this. Most people want to remove the banding, so it's hard to find resources for creating it.