Canon RF-S 18-45mm f/4.5-6.3 IS STM vs Tamron 17-70mm f/2.8 Di III-A VC RXD

Both are Canon RF mount zooms for everyday and travel — here's how the specs differ and which to pick. Every spec is from the manufacturer's own catalog.

Last verified 2026-09-01 · Canon RF mount · prices change — check the retailer

Spec	Canon RF-S 18-45mm f/4.5-6.3 IS STM	Tamron 17-70mm f/2.8 Di III-A VC RXD
Focal length	18-45mm	17-70mm
Max aperture	f/4.5-6.3	f/2.8
Type	zoom	zoom
Coverage	APS-C	APS-C
Mount	Canon RF	Canon RF

Which should you buy?

the Tamron 17-70mm f/2.8 Di III-A VC RXD opens wider (f/2.8) — brighter in low light and more background blur
the Canon RF-S 18-45mm f/4.5-6.3 IS STM covers 18-45mm and the Tamron 17-70mm f/2.8 Di III-A VC RXD covers 17-70mm — pick the range that matches what you shoot
the Canon RF-S 18-45mm f/4.5-6.3 IS STM is first-party (Canon) for guaranteed full autofocus and in-camera corrections; the Tamron 17-70mm f/2.8 Di III-A VC RXD is third-party — usually the value pick

Where to buy

Canon EOS R50 Mirrorless Camera with RF-S18-45mm F4.5-6.3 is STM & RF-S55-210mm F5-7.1 is STM Lenses, 24.2 Megapixel CMO

Canon RF-S 18-45mm f/4.5-6.3 IS STMSee price on Amazon

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Tamron 17-70mm F/2.8 Di III-A VC RXD Standard Zoom Lens for Canon RF APS-C Mirrorless Cameras

Tamron 17-70mm f/2.8 Di III-A VC RXDSee price on Amazon

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FAQ

What's the difference between the Canon RF-S 18-45mm f/4.5-6.3 IS STM and the Tamron 17-70mm f/2.8 Di III-A VC RXD?
The Canon RF-S 18-45mm f/4.5-6.3 IS STM is 18-45mm f/4.5-6.3 zoom, APS-C; the Tamron 17-70mm f/2.8 Di III-A VC RXD is 17-70mm f/2.8 zoom, APS-C. Both fit the Canon RF mount.

Which is better in low light, the Canon RF-S 18-45mm f/4.5-6.3 IS STM or the Tamron 17-70mm f/2.8 Di III-A VC RXD?
The Tamron 17-70mm f/2.8 Di III-A VC RXD — its f/2.8 maximum aperture lets in more light and gives more background blur than the f/4.5-6.3 of the other.

Do the Canon RF-S 18-45mm f/4.5-6.3 IS STM and Tamron 17-70mm f/2.8 Di III-A VC RXD fit the same camera?
Yes — both are Canon RF mount lenses, so they fit Canon EOS R series (full-frame R5/R6/R8) and APS-C (R7/R10/R50).

Citing these specs? Go ahead — manufacturer data, last verified 2026-09-01. Copy a ready-made reference:

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Canon RF-S 18-45mm f/4.5-6.3 IS STMAffiliate linkSee price on Amazon