Many camera manufacturers choose to support, or at least turn a blind eye to, third-party lens makers. Some even wholeheartedly embrace them. However, Canon has infamously taken a stance to deny third-party manufacturers access to its RF mount. The fascinating twist is that many companies were beginning to produce manual and autofocusing lenses before the crack-down, creating an exclusive market of very rare lenses that hit the streets before the curtain fell.
