3D device mockups, used deliberately

A flat mockup is an image of a device with your screenshot pasted into a rectangle. A 3D mockup is an actual model, lit and photographed by a virtual camera, which means you can move around it, animate it and get real reflections along the edges. The extra dimension is powerful and easy to overuse.

What 3D actually buys you

Three things a flat template cannot do: arbitrary angles, so you are not stuck with the four poses somebody baked into a PSD; consistent lighting across devices, so a phone and a laptop in the same image agree about where the light is; and motion, because once the device is a model, the camera can move and you have a video instead of a still. If none of those matter for the asset you are making, a flat mockup is faster and just as good.

Perspective is a budget you spend

Every degree of rotation costs legibility. A screen turned 30 degrees from the camera loses roughly a third of its apparent width and compresses type on the far side. The practical rule: if the interface must be readable, stay within about 15 degrees of head-on and use the angle purely to hint at depth. Save the dramatic three-quarter poses for images where the device is a shape in a composition and the screen content is decorative.

Field of view is the hidden control

Two renders at the same angle can feel completely different depending on focal length. A wide field of view exaggerates the near edge and makes a phone look like it is swinging toward you like a door; a narrower one flattens perspective and keeps the screen rectangular. When a mockup looks subtly wrong despite correct angles, the field of view is usually the culprit. Start narrow and only widen when you deliberately want drama.