How big a problem is an f/11 telephoto? Canon’s new lenses look mad… but aren’t

Canon RF 800mm F11 IS STM
(Image credit: James Artaius)

Canon has caused quite a storm. As well as releasing the ground-breaking EOS R5 and EOS R6, it has launched two new inexpensive telephoto prime lenses for its EOS R cameras, the RF 600mm f/11 IS STM and RF 800mm f/11 IS STM, both with a fixed aperture of f/11. That is a VERY small aperture for a telephoto lens, but is it really the problem that many people might imagine?

Is an f/11 telephoto a problem?

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LightingEVShutter speedApertureISO
Bright snow/sand161/500secf/11ISO 125
Sunny151/500secf/11ISO 250
Slight overcast141/500secf/11ISO 500
Overcast131/500secf/11ISO 1,000
Heavy overcast121/500secf/11ISO 2,000
...Row 5 - Cell 1 Row 5 - Cell 2 Row 5 - Cell 3 Row 5 - Cell 4
Indoor sports91/500secf/11ISO 16,000

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Rod Lawton

Rod is an independent photography journalist and editor, and a long-standing Digital Camera World contributor, having previously worked as DCW's Group Reviews editor. Before that he has been technique editor on N-Photo, Head of Testing for the photography division and Camera Channel editor on TechRadar, as well as contributing to many other publications. He has been writing about photography technique, photo editing and digital cameras since they first appeared, and before that began his career writing about film photography. He has used and reviewed practically every interchangeable lens camera launched in the past 20 years, from entry-level DSLRs to medium format cameras, together with lenses, tripods, gimbals, light meters, camera bags and more. Rod has his own camera gear blog at but also writes about photo-editing applications and techniques at