One focal length, and usually the widest aperture the money buys · review

Canon RF 45mm F1.2 STM, under 400 g review

The widest aperture in this entire lot at F1.2 for 439 €, in a barrel the page says weighs less than 400 g — a ceiling rather than a figure — with no blade count, no thread and no close-focus distance published.

By Jean-Benoit Buisson

The bottom line F1.2 for 439 € is the headline and it is a real one: nothing else of the eight here opens that wide. The page then declines to publish a blade count on a lens sold for bokeh, gives a weight ceiling instead of a weight, and leaves the thread and the close-focus distance out entirely.

On the listing

Five bullets. A bright 45mm prime whose extremely high F1.2 speed is offered as creative freedom; an F1.2 aperture credited with striking subject separation and soft background bokeh, named for expressive portraits; a built-in STM motor for fast, quiet, smooth autofocus, with a configurable control ring giving direct access to important camera settings; a travel bullet saying the lens weighs less than 400 g and suits street portraits, fitting easily into any camera bag; and a compatibility bullet naming the Canon EOS R System.

F1.2, and what it costs to make one

The widest aperture of the eight here. Two-thirds of a stop past the Sigma below it and a stop and a third past the F1.8 lenses, which is roughly two and a half times the light at the same shutter speed. Lenses that open this far are normally heavy and dear; this one is neither by the standards of its aperture.

Less than four hundred grams is a ceiling, not a weight

The fourth bullet states a threshold. Two lenses on this shelf publish 230 g and 156 g, and those can be set beside each other. This one can be said to be under 400 g and nothing more precise, which is a different kind of claim and is worth reading as one.

A ring that replaces a hand

With no zoom to turn, the control ring is the only thing the left hand does on this lens besides focus. Assigned to aperture or exposure compensation, it moves a setting off the camera body and under the fingers already holding the lens.

A phrase from another product, again

The fourth bullet calls this an action camera lens in the middle of a sentence about street portraits. It is a template artefact, like the video resolution field on the 24mm pancake two shelves over, and it describes nothing about a 45mm F1.2 prime.

Sold on bokeh, silent on the aperture that makes it

No blade count, no shape. Also no thread, no minimum focus distance and no sealing claim — four of the nine lines this shelf compares, blank on a 439 € lens.

Availability

Between 439 € and 499 € on the German, French, Italian and Spanish Amazon stores when this page was last checked.

The British Amazon store carry it too, priced in local currency. Those amounts are deliberately absent from the range above, which reads euro stores only.

Nothing came back from the American Amazon store at all, so the button for that country runs a search instead of opening an entry that is not there.

Everything in this section is the figure Keepa carried on the day of the last update to this page. Availability and prices shift without notice.

Prices quoted in this text were read on 13 September 2026. The live price is at the top of the page.

What it does well, and what it gives up

Strengths

F1.2, the widest maximum aperture of the eight here by two-thirds of a stop
A configurable control ring alongside the STM motor, giving direct access to a camera setting from the barrel
Under 400 g for an F1.2 lens, which is light for that aperture whatever the exact figure

Compromises

The weight is given as a ceiling rather than a number, so it cannot be compared with the published figures on this shelf
No blade count, on a lens whose second bullet sells the bokeh
No filter thread, no minimum focus distance and no sealing claim

Specifications

Focal length	45mm, fixed, in the title. Slightly wider than the traditional 50mm normal lens and noticeably tighter than a 35mm, and the page never publishes an angle of view to place it
Format	Not stated directly. The title and the fifth bullet name the Canon EOS R System, which includes both full-frame and APS-C bodies, and no bullet says which this lens was computed for. The RF designation without an S is Canon’s full-frame marking, but the page itself never states the format, so nothing here should be read as a claim
Maximum aperture	F1.2, in the title and in the first two bullets. It is the widest maximum aperture among the eight here — two-thirds of a stop past the F1.4 Sigma and a full stop and a third past the F1.8 lenses — and the second bullet names what it is for: subject separation and soft background bokeh in portraits
Blade count and shape	Not published on the listing. The second bullet sells the bokeh as the reason to buy, and the number that shapes it appears nowhere
Autofocus motor	STM, named in the third bullet for fast, quiet, smooth autofocus. The same bullet names a configurable control ring giving direct access to camera settings, which is the RF system’s own control and is worth more than it sounds on a lens with no zoom ring
Minimum focus	Not published on the listing, and no magnification ratio. A fast normal lens is often used close, and the page gives nothing
Filter thread	Not published in millimetres. Five bullets, and no diameter
Sealing	Not claimed. Street portraits and travel are named as uses and no protection against dust or moisture is stated
Weight	Stated as less than 400 g in the fourth bullet, which is a ceiling and not a measurement. The lens weighs something below that figure and the page does not say what — a different kind of statement from the 230 g and 156 g published elsewhere on this shelf, and it cannot be compared with them
Amazon reference	B0G12GQQG8 (same reference on 5 Amazon marketplaces)
EAN	4549292248982

What people ask before they commit

How much does F1.2 give over F1.8?

A stop and a third, which is about two and a half times the light at the same shutter speed. It also gives a shallower depth of field at the same distance, which is what the second bullet means by subject separation. Both effects are why F1.2 lenses are large and expensive; this one is 439 € in Germany and 405 € on the British shelf, which is modest for the aperture.

Why does the page say less than 400 g instead of a weight?

That is how the fourth bullet is written, and the distinction matters. A ceiling tells you the lens is under a threshold; a measurement tells you where. Two lenses on this shelf publish 230 g and 156 g and can be compared directly with each other. This one can only be compared with the threshold it was written against.

What is the control ring for?

The third bullet calls it configurable and says it gives direct access to important camera settings. On Canon’s RF mount that ring is normally assigned to aperture, exposure compensation or sensitivity, and it is set in the camera menu. On a prime, where there is no zoom ring competing for the same hand position, it is the most useful control the lens can carry.