Canon RF-S 18-45mm f/4.5-6.3 IS STM vs Sigma 17-40mm f/1.8 DC Art

Both are Canon RF mount zooms for everyday — 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	Sigma 17-40mm f/1.8 DC Art
Focal length	18-45mm	17-40mm
Max aperture	f/4.5-6.3	f/1.8
Type	zoom	zoom
Coverage	APS-C	APS-C
Mount	Canon RF	Canon RF

Which should you buy?

the Sigma 17-40mm f/1.8 DC Art opens wider (f/1.8) — 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 Sigma 17-40mm f/1.8 DC Art covers 17-40mm — 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 Sigma 17-40mm f/1.8 DC Art 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

Amazon links are affiliate links — we may earn a commission at no extra cost to you.

Sigma 17-40mm F1.8 DC | Art for Canon RF, Black

Sigma 17-40mm f/1.8 DC ArtSee price on Amazon

As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Affiliate links never affect our specs or which lenses we compare.

FAQ

What's the difference between the Canon RF-S 18-45mm f/4.5-6.3 IS STM and the Sigma 17-40mm f/1.8 DC Art?
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 Sigma 17-40mm f/1.8 DC Art is 17-40mm f/1.8 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 Sigma 17-40mm f/1.8 DC Art?
The Sigma 17-40mm f/1.8 DC Art — its f/1.8 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 Sigma 17-40mm f/1.8 DC Art 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:

More Canon RF comparisons: Canon RF-S 18-45mm f/4.5-6.3 IS STM vs Tamron 17-70mm f/2.8 Di III-A VC RXD · Canon RF 15-35mm f/2.8 L IS USM vs Canon RF 16-28mm f/2.8 IS STM · Canon RF 24-50mm f/4.5-6.3 IS STM vs Canon RF 28-70mm f/2.8 IS STM · Canon RF 24mm f/1.4 L VCM vs Canon RF 20mm f/1.4 L VCM · all Canon RF lenses · all comparisons

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