Canon recently launched the Canon EOS R7 and EOS R10 – two affordable new mirrorless cameras with APS-C sensors – along with the RF-S 18-45mm F4.5-6.3 IS STM and RF-S 18-150mm F3.5-6.3 IS STM lenses.
If you’re not familiar with 'crop-sensor' cameras, the big advantage of the smaller APS-C sensor compared to the best full frame cameras is the 1.6x crop which extends your effective focal length of lenses.
This is ideal for wildlife and sports when, for example, a 400mm focal length effectively becomes (1.6 x 400mm) 640mm. Suddenly that tiny blue tit hiding at the end of the garden becomes a frame-filling photo.
While how about putting a Canon RF 800mm f/11 on an EOS R7 or R10 to create a ridiculous 1280mm amount of reach. You could practically stay in the car park to photograph the football!
• Read more: full frame vs cropped sensor for bird photography - which is better?
However, while it’s an advantage having extra reach for subjects far away or for smaller wildlife, it’s a disadvantage when you only have 18mm for, say, big landscapes or city scenes – 18mm x 1.6 is 29mm, which isn’t very wide at all in the real world. This really restricts what you can shoot with the current two RF-S 18-45mm F4.5-6.3 IS STM and RF-S 18-150mm F3.5-6.3 IS STM lenses.
Canon RF-S lenses vs Canon EF-S lenses
Will Canon’s new RF-S lenses only fit APS-C EOS bodies you may be asking? This is the big question. The marked difference between Canon EF-S lenses and Canon RF-S lenses is that EF-S lenses will only fit on crop-sensor APS-C Canon EOS DSLR like the EOS 850D, EOS 90D and EOS 7D Mark II. You simply can’t use EF-S lenses on full-frame EOS DSLRs as they have an EF mount.
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Whereas RF-S lenses will fit on both APS-C Canon EOS mirrorless cameras like the R7 and R10, and full-frame EOS mirrorless cameras like the EOS R6 and EOS R5; however on these cameras, they will switch to crop mode effectively turning your full-framer into an APS-C camera.
So why you can use RF-S lenses, why you’d want to put budget lenses on top spec mirrorless EOS R cameras is probably the real question. It’s like investing in a Ferrari then driving in first gear all the time. A better way round would be to put top lenses on budget bodies for better photos!
What Canon RF-S lenses will we see next?
At the big press launch in London of the new EOS R7 and R10 and RF-S lenses, Canon remained resolutely tight-lipped about any sort of Canon RF-S lens roadmap, but we’d be amazed if we don’t see at least some of the equivalent EF-S lenses with RF-S mounts and specs soon.
There are rumors rattling around online of patents for some Canon RF-S wide zooms, and with only 18mm available at the moment as the widest focal length for APS-C Canon mirrorless, it’s clear they’ll need to release an RF-S 10-22mm or similar focal length range to offer crop-sensor EOS R mirrorless users an equivalent 16-35mm full-frame.
You can use RF lenses on these APS-C EOS R bodies, however, using something like the high-priced (£2389/$2399) and heavy-weight Canon RF 15-35mm F2.8L IS USM kind of defeats the object and is out the question for entry-level enthusiasts, not to mention how nose heavy a diddy EOS R10 would feel with such a beast of a lens strapped to the front.
You can also use older Canon EF-S and EF lenses with the Canon Mount Adapter EF-EOS R on an EOS R7 or R10, but you won’t benefit from the latest technology as EF-S lenses won’t communicate as well as RF-S with EOS R bodies – eg IS and IBIS or AF won’t work or be as effective.
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