When and when not should i use proportionally-to-screen sizes

Question

I'm designing my app (targeting only iOS/iPhone devices).

Currently, there couple components, which I'm designing to fit into iPhone 5 screen(smallest screen). On largers screens(iPhone 6, 6+), I'm centering the components and just give it more margin from the sides.

Note: In all of the images, the "red" area is at the same size(width and height), only the screen size changes

---

Should I or should I not increase the size proportionally? Is there are a known guidelines? Should I keep the font size and only increase the images?

Example:

Answer 1

You'll want to choose your font and image sizes to be comfortably usable on the smallest screen, which might result in short lines and little space for images. But that's a function of physics, for which you're not responsible (you are responsible for user comfort, of course, within reason).

Once I had those sizes selected, I wouldn't increase them with an increase in screen size, I'd allow more information to appear. It's not hard to see why: imagine translating an increase in size to a desktop screen. The same principle operates: bigger isn't necessarily better, if you've sized it correctly in the first place.