One reason you shouldn't is that Photoshop saves palette data backwards in PCX images, if I recall, so you might run into headaches when importing them in HuC/MagicKit.
Haha ... I hadn't hit that one ... guess that my artists in the Photoshop era always exported in BMP/TGA/PNG ... but thanks, it's good to know that the problem is there.
He can always export in a different format and then use IrfanView or something else to convert it into a PCX if he needs to ... but that's a bit of an ugly work-around.
Sorry for the noob intervention here.
No apology needed ... we all had to start somewhere ... and this seems like a good place to ask.
You said that you're using a "modern" engine ... do you mean that you're doing a "retro" project in something like Unity, or that you're actually targeting real PCE hardware in something like HuC?
I have been creating artwork that retains the limitations of # of colors, and resolution. The engine I am using is modern and does not limit these things, so I have to manage this manually.
I'm not sure exactly what you mean here about the number of colors ... do you mean the 16-per-character or 256-per-background/spriteset, or maybe the 512-color-3-bit-rgb-palette ?
The PCE has the usual 4th-generation 16-colors-per-individual-character-or-sprite ... but most people at the time used programs like Deluxe Paint or Deluxe Anim in 256-color mode to "simulate" up to 16 different 16-color palettes ... perfect for the PCE's 16-palette backgrounds and 16-palette sprites.
I only use photoshop, pixel brushes and not anti aliasing on shapes and selections. I am very careful with what colors are in the image, and export them with a limited pallet to ensure there are no extra colors.
Is there a reason I should not be creating my sprite sheets only in photoshop, or is it a convenience thing for porting down to PCE specifically?
Use whatever feels comfortable to you that still lets your programmer get the data in a format that they can use ... that's your only real limit ... and the only thing that really matters.
There's no "absolutely-the-only-way" here ... only things that are easier and harder.
Photoshop was specifically written to do 24-bit "true-color" graphics and replace the old 256-color-or-less paletted graphics programs.
It sort-of handles paletted graphics ... but it's workflow really isn't designed around them.
I know that people have used it to do those ... but I suspect that most artists quickly move on to something else like "ProMotion" or maybe the "grafx2" or "NeoPaint" that have been mentioned, that make it
easy to work with and manipulate paletted graphics.
By the 6th-generation (i.e. PS2), Photoshop use was very common ... but often combined with Macromedia (now Adobe) Fireworks, which was one of the few programs at the time (and even now AFAIK) that could handle paletted-alpha.
If you'd be happier with a recommendation, then personally, I'd probably point you at "grafx2" right now ... but it's really up to you (and your programmer).