I generally only take my smartphone, but on very long trips, I take an iPad. It's mostly for morale support: watching a movie in the tent, and such. I've been eyeing those Microsoft Surface tablets. They run a full Windows OS, have a USB port, and would be able to handle all my computing and photography/photoshop needs, unlike an Apple or Android tablet.
Can do all that on my samsung tablet. The USB port is available via an adapter but the microsd/usb adapter is another solution that does pretty much the same thing. There are already several apps for photos editing available and a better version of photoshop is coming at the end of this year.
Adobe discontinues Photoshop Touch, previews its next generation - CNET
Artflow is a nice little app allowing digital painting
Here is photo editing app for ipads
Pixelmator for iPad review - CNET
The microsoft surface isn't the only one outthere with windows, the dell venue 11 pro is another one worth a try.