What is fSpy and what does it do?

Updated

fSpy is an open source, cross-platform application for still image camera matching. It lets you recover the camera parameters used to take a photograph — field of view, camera position, orientation, and principal point — so you can recreate that same virtual camera in 3D software and composite new objects into the original image. It runs on Mac, Windows, and Linux, is developed by Stuffmatic, and is free to download and use.

What problem it solves

If you want to place a 3D object into a photo and have it look like it belongs there, your virtual camera has to match the real one. Guessing the focal length and angle by eye rarely lines up. fSpy extracts those parameters from the image itself, so the 3D camera you build matches the perspective of the photo.

Typical uses:

  • Compositing a 3D model into a still photograph
  • Matchmoving a single image for visual effects or architectural visualization
  • Rebuilding a scene's camera setup for rendering or set extension

How the workflow fits together

  1. Match in fSpy — load the still image and define the perspective (for example, by marking parallel lines or vanishing directions). fSpy computes the camera parameters.
  2. Get the parameters into your 3D app — either through a dedicated importer or by copying values manually.
  3. Composite — use the matched camera and the original image as a background to place your 3D content.

Importing into Blender

Blender has an official fSpy importer add-on. It sets the Blender camera parameters for you and can optionally set the camera background image. This is the smoothest path and avoids manual value entry.

Importing into other applications

For applications without a dedicated importer, you transfer the parameters by hand. The general process:

  • Set the camera viewport to match the dimensions of the input image
  • Use the input image as the camera background
  • Set the camera field of view
  • Set the camera position
  • Set the camera orientation
  • Set the principal point, unless it coincides with the image midpoint

Availability and cost

fSpy is open source software and free to download and use. The project also offers a donate button (via PayPal) for anyone who wants to support it — paying is optional, and you choose the amount.

When to use it

Use fSpy when you have a single still image and need a matching virtual camera. If you already have a dedicated importer for your target application (as with Blender), the process is largely automatic; otherwise, expect to copy the parameter values across manually.