Formerly Blam for Blender, fSpy is Now a Free Stand-Alone Camera Matching App for Mac Windows and Linux.
Matching perspective to a still image is quite a challenge in 3D. There are a lot of things to take into consideration, and most of those things are questions about the camera that need answering. There are quite a few tools around for various DCC’s that get the job done, and now there is another in fSpy.
fSpy used to be Stuffmatic’s Blender Add-on “Blam” that let you quickly match the real camera to your 3D camera, by directly drawing out perspective lines on the still image. Now that addon has graduated to a stand-alone free and open source application for Mac, and Linux.
The stand-alone app is only for calculating camera details on still images and has direct integration with Blender. If you use another DCC, not to worry, you can copy and paste the information out of the app and into your favorite 3D app.