A roundup of explainers – choose your flavour.
Focal Reducers / Speed Boosters | Explained (via CVP):
How Crop Factor Affects Focal Reducers & Macro Reproduction (via Gerald Undone):
The Effects of Sensor Size and Foal Reducers (via Anamorphic on a Budget):
Further Viewing
A related, but separate concept is aspect ratio:
Related Posts:
Film School: Practical Lighting Placing light sources within shots - and how it can improve them.
Film School: Dear YouTubers… Stop doing these things - they're easy enough, and we'll all win.
Audio School: Capturing Cleaner Audio Tips and tricks as useful for those just starting out, as for those who want to improve their process.
Audio School: Fix It In Post Ways to work with less-than-ideal audio in your video edit.
Film School: Goodbye Green Screen, Hello ‘The Volume’ A look at the virtual set used in 'The Mandalorian'.
Film School: the EL Zone System The new false colour standard?
Film School: Digital Cinema Camera Workflow An overview of how major movies are shot on digital cameras, from camera setup to final export.
Film School: Cinematography Prep A overview of pre-production work behind what the camera sees.