Canon's RF-S zooms for crop sensors all have variable apertures. Rumors hint that could change with an f/4 prosumer zoom

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There's talk of a 15-70mm f/4 constant-aperture lens to accompany the Canon EOS R7 II camera, with both rumored for release this summer

Canon RF-S 18-150mm f/3.5-6.3 IS STM
Canon doesn't currently have a constant aperture zoom RF-S lens for crop sensor cameras – this RF-S 18-150mm pictured is an f/3.5-6.3 (Image credit: James Artaius)

Canon's RF-S series, meant for APS-C mirrorless bodies, is filled with affordable optics – but will the series offer a constant aperture zoom in the future? That's the idea floating around the latest Canon lens rumors.

If the rumors are true, then Canon could be about to treat its EOS R APS-C community to a do-it-all lens featuring not only a versatile focal length range, but also a constant aperture that verges on fast-glass capabilities at the maximum zoom length.

According to Canon Rumors, an unnamed source has said that the forthcoming lens is the RF-S 15-70mm F4 IS STM, which first came to public attention back in 2023 when the design was revealed in patent number P2023057875 – published on the Japan Patent Office platform.

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While generous on the wide-angle end, you might be thinking that 70mm hardly embodies an all-rounder focal length. But, taking the RF-S crop factor into consideration, and you’ve got a 24-105mm full-frame equivalent lens.

Now factor in the constant f/4 aperture, and suddenly this lens becomes a very attractive prospect, boasting versatility not seen in the likes of Canon’s existing RF-S telephoto zoom lenses like the RF-S 55-210mm F5-7.1 IS STM and RF-S 18-150mm F3.5-6.3 IS STM.

A diagram of the 15-70mm design as seen in patent number P2023057875 (Image credit: Canon)

While Canon Rumors didn’t state an announcement date for the rumored RF-S 15-70mm F4 IS STM, it’s speculated that it will be released alongside the equally-rumored Canon EOS R7 II camera, which rumor sites have heavily touted for release this summer.

The word is that the EOS R7 II is going to be geared towards ‘prosumer’ APS-C photographers, and my colleague, Peter Travers, thinks it may even feature a BSI (Back-Side Illuminated) sensor in the region of 40MP.

Dare I say that the suspected 15-70mm f/4 STM could even be a kit lens for the rumored EOS R7 II in a bid to capture a healthy amount of the prosumer market?

With nothing confirmed by Canon, as yet, we’ll have to wait for more information. Regardless, it’s exciting times for Canon fans who could be getting a long-awaited piece of kit.

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Alan Palazon
Alan Palazon
Staff Writer

I’m a writer, journalist and photographer who joined Digital Camera World in 2026. I started out in editorial in 2021 and my words have spanned sustainability, careers advice, travel and tourism, and photography – the latter two being my passions.

I first picked up a camera in my early twenties having had an interest in photography from a young age. Since then, I’ve worked on a freelance basis, mostly internationally in the travel and tourism sector. You’ll usually find me out on a hike shooting landscapes and adventure shots in my free time.

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