The Canon RF 50mm f/1.8 STM is a compact, light prime that suits everyday photography, while the RF 45mm f/1.2 STM offers a much wider aperture in a larger body. Choose the 50mm f/1.8 for simplicity and easy carrying; choose the 45mm f/1.2 when low light and soft backgrounds matter more than size. Check Canon’s product pages for exact specs.
Two Fast Primes, Two Goals
Both are prime lenses for Canon RF mirrorless cameras with an STM focus motor, and both are close to a natural field of view. The 50mm f/1.8 is often described as a basic entry-level prime because of its small size and straightforward design. The 45mm f/1.2 is a step up in light gathering, aimed at photographers who want that extra bright aperture without moving to a heavy professional lens.
The aperture gap is large. f/1.2 lets in roughly twice the light of f/1.8 and gives a more dramatic background blur at the same distance. That matters in dim rooms, at night and for portraits.
Side by Side
| Trait | RF 50mm f/1.8 STM | RF 45mm f/1.2 STM |
|---|---|---|
| Focal length | 50mm | 45mm |
| Maximum aperture | f/1.8 | f/1.2 |
| Size and carry | Very compact | Larger and heavier |
| Best for | Everyday, travel, beginners | Low light, portraits, blur |
| Focus motor | STM | STM |
How to Choose
- Decide how often you shoot in dim light. If it is regular, the f/1.2 aperture offers real value.
- Think about carry. A small lens stays in your bag, while a larger one may stay at home.
- Consider depth of field. At f/1.2, the zone of sharp focus is very thin, which looks striking but needs careful focus placement.
- Think about your other lenses. If you already own fast zooms, the f/1.8 adds a small and light option, while the f/1.2 adds something your zooms cannot do.
- Confirm weight, filter size and features on Canon’s page before deciding.
Practical Settings
These are general baselines to adjust as you learn how each lens behaves.
- For portraits, an aperture around f/1.8 to f/2.8 is a flexible zone on either lens, with f/1.2 reserved for dramatic blur.
- For street and travel, an aperture of roughly f/4 to f/8 gives more forgiving focus.
- For handheld shots of moving people, a shutter speed of roughly 1/200 and faster is a sensible floor.
- For night scenes with still subjects, roughly 1/60 and above works for many people with steady hands and a stabilized body.
FAQ
Is the 50mm f/1.8 good enough?
For many photographers it is. It is sharp enough for common uses, light to carry and a good way to learn prime lens shooting.
Is the 45mm f/1.2 hard to focus?
Not hard, but the thin depth of field means small focus errors are more visible, especially up close.
The Short Version
The 50mm f/1.8 STM is the small, simple everyday prime, and the 45mm f/1.2 STM is the bright, dramatic one. Choose the f/1.8 for portability and the f/1.2 for low light and strong background blur.
