As a UI Designer, I consistently make cartoon GUI’s, however, I would like to delve deeper into the Realistic Gui Category to expand my knowledge. I have been pondering about what software I should use for making Realistic UI’s and I have decided to come here for any suggestions. I can use both free and non-free software if this makes your understanding clearer.
If you can afford it, use Photoshop or Adobe Illustrator.
PHOTOSHOP
With photoshop you can make overall nice, realistic GUIS with basically anything you want with them. Photoshop has a wierd learning curve, but when you get the basics down it is incredible.
Illustrator
Adobe Illustrator is an amazing program used to make cartoony and vector images. It is an amazing software which is easier to learn than Photoshop (imo).
It is your choice what to use at the end of the day. Paint Net is a pretty good software that has some of the features the Photoshop has and is really popular.