Canon's revolutionary 800mm at f/11 — diffractive optics with IS in ultra-compact design.
The Canon RF 800mm f/11 IS STM was released approximately 2020 as a compact fixed-aperture super-telephoto prime for Canon RF-mount full-frame using a diffractive optics element. Eleven elements in 9 groups with diffractive optics. Ten aperture blades. No front filter thread; 40.5mm drop-in filter slot. At 1,260g. 6.0m MFD. IS rated 4 stops. STM autofocus.
Eleven elements in 9 groups (DO diffractive optics element). Ten aperture blades. No front filter thread — 40.5mm drop-in filter slot only. At 1,260g. Minimum focus distance of 6.0m. STM for quiet AF. IS rated 4 stops. Fixed f/11 aperture — no aperture control. Full-frame coverage. Canon RF mount.
The f/11 fixed aperture is the defining trade-off: the DO (Diffractive Optics) element and f/11 fixed aperture enable Canon to produce an 800mm prime at 1,260g versus the 2,500-3,000g of conventional 800mm telephoto primes. The f/11 aperture requires adequate light (daylight, bright overcast) and fast sensors. The 40.5mm drop-in filter provides ND and polariser capability without a practical front filter thread.
On the used market the Canon RF 800mm f/11 IS STM is affordable as an RF super-telephoto prime. Condition checks: STM AF response, IS engagement, 40.5mm drop-in filter slot. Note: fixed f/11 — no aperture adjustment. No front filter thread. Compatible with Canon RF full-frame and APS-C bodies.