Kamil Pekala explains how teleconverters and speedboosters actually work and why focal length extenders reduce image brightness and also why speedboosters make a bigger aperture - sort of. You will also understand what are the trade offs and limitations of both focal length extenders and reducers. Ever wondered why speedboosters are only made for APS-C or Micro 4/3 cameras? In this video you'll learn why is that.