Answered: What is the Canon RF 100-500mm F4.5-7.1 L IS USM Lens's Max Aperture at 400mm?

For many, especially those already owning the impressive Canon EF 100-400mm f/4.5-5.6L IS II USM Lens, the narrow to-f/7.1 spec on the Canon RF 100-500mm F4.5-7.1 L IS USM Lens gave us pause. None of us was disappointed by the to-500mm part of the spec, but we wanted to know if the aperture opening size was being sacrificed at the 400mm aperture in order to keep this lens compact and light. Thanks to Drew MacCallum's (Canon USA) effort to answer this question for us, now we know.

What is the Canon RF 100-500mm F4.5-7.1 L IS USM Lens's maximum aperture opening at 400mm?

Answer 1: When the camera is set to 1/3-stop increments, the maximum 400mm aperture reported to the camera is rounded to f/6.3.

Answer 2: When the camera is set to 1/2-stop increments, the maximum 400mm aperture reported to the camera is rounded to f/5.6.

I know, you are now planning to change your R5 and R6 to use 1/2-stop increments. Don't bother as the difference is how the actual opening size is rounded (the true aperture is likely between these two numbers), likely holds for only a short range of focal lengths, and even if there was a 1/3-stop difference, the difference in noise made visible by an offsetting 1/3-stop ISO change will not matter to most.

The Canon RF 100-500mm F4.5-7.1 L IS USM Lens Review page is loaded with expectations. This lens should be awesome.

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