A pinhole camera does not focus in the same way a lens does, because there is no lens to converge rays onto a specific plane. So there is no adjustable focus plane.

However, sharpness is still limited. Each scene point forms a small blur spot (often described as a circle of confusion) rather than a perfect point. That blur is mainly set by the pinhole diameter, plus diffraction when the hole is very small.

In practice, pinhole cameras have effectively infinite depth of field: objects at different distances are rendered with similar sharpness compared with a lens camera. But that does not mean perfectly sharp. If the pinhole is too large, geometric blur increases; if it is too small, diffraction softens the image. That is why there is an optimum pinhole size for a given pinhole-to-film distance.

So the useful way to think about it is:

• no lens-style focusing mechanism
• effectively infinite depth of field
• image sharpness determined by pinhole size and diffraction

A pinhole image is therefore "all in about the same focus," but never perfectly focused in the lens sense.