Why does using a tilt-shift lens make things look miniature?

Question

This question isn't so much about how to achieve the effect of making a scene look like it's modelled in miniature, but why tilting the focal plane creates the effect. What is it about photographing miniatures that makes them look like miniatures, and how is this replicated by tilting the focal plane?

I can understand how when photographing a model of a scene, you have a much higher magnification, which leads to a shallower depth of field compared to when capturing the real-sized scene, but how does tilting the focal plane help? Is it just that you have the focal plane tilted relative to the plane that most of your subject is on, so that you can achieve a narrower depth of field for the focal length and aperture, or is there more to it than that?

Asked by Edd

Answer

The reason tilt-shift "sells" the miniature effect to the eye is that it allows both the foreground and background to be out of focus. We are accustomed to seeing images of city scenes, for example, where the foreground is a bit blurry, or the distant background is out of focus, but not both. Normal lenses shooting these scenes near infinity focus will have enough depth of field that you wouldn't have a situation where both foreground and background are strongly out of focus.

When photographing real miniatures, you are focusing much closer so have much narrower DOF, so you do get background and foreground out of focus.

I believe the tilt-shift lens achieves this effect because it creates a plane of focus that is not parallel to the sensor, so it exaggerates out of focus areas. I believe you can further limit the DOF by focusing closer then using the tilt to move the in-focus area to your subject. So a combination of closer focus and stretching the plane of focus so that less of it coincides with the sensor.

Answered by MikeW

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