A Polish software engineer (and amateur photographer) named Michael Bemowski recently put together one of the most helpful depth of field tools out there, and the best part is that it's completely free. The tool, which you can find here, allows you to manipulate every camera and lens setting that affects depth of field, from sensor size to focal length, from aperture to the distance between the subject and the camera. Plus it gives you a handy visual approximation of what each specific set of parameters would look like in a real world setting.

n order to make this tool as accessible as possible, you can download a version of it that runs offline on any operating system, and there is a dedicated mobile version as well, so you can access it anywhere at any time.