My game runs fine on iphone4s but slow on iphone4.
Is there a way to turn on retina for iphone4s but use standard res for iphone4 (same for ipad3 vs ipad4) ?
Yep! You certainly can with unity 4. You can even go 75% retina, or 25% if you’d like. It’s all done via the Screen.SetResolution() method
Screen.SetResolution(240, 160, true)