Canon RF50mm F1.8 STM Lens, Fixed Focal Length Prime Lens vs Sigma 18-
Updated July 2026 — Canon RF50mm F1.8 STM Lens, Fixed Focal Length Prime Lens wins on price and low-light, Sigma 18- wins on versatility and optical quality.
The Canon RF50mm F1.8 STM lens offers excellent low-light performance and is more budget-friendly, while the Sigma 18-50mm F2.8 DC DN Contemporary lens provides versatility with its zoom capabilities.
Why Canon RF50mm F1.8 STM Lens, Fixed Focal Length Prime Lens is better
Price
Canon lens is significantly cheaper at $219.
Low-Light
Canon lens has a larger f/1.8 aperture for better low-light performance.
Compactness
Canon lens is more compact and lightweight.
Why Sigma 18- is better
Versatility
Sigma lens offers a zoom range of 18-50mm.
Optical Quality
Sigma lens features superb optical quality.
Aperture Consistency
Sigma lens has a constant f/2.8 aperture.
Overall score
Specifications
| Spec | Canon RF50mm F1.8 STM Lens, Fixed Focal Length Prime Lens | Sigma 18- |
|---|---|---|
| Focal Length | 50mm | 18-50mm |
| Aperture | f/1.8 | f/2.8 |
| Weight | 0.66 lbs | 0.75 lbs |
| Compatibility | EOS R | Sony E |
| Zoom | No | Yes |
Dimension comparison
Overview of the Canon RF50mm F1.8 STM Lens
The Canon RF50mm F1.8 STM lens is a compact and lightweight prime lens designed specifically for the EOS R series mirrorless cameras. Priced at $219.00, it offers impressive features for low-light photography and creative compositions. The lens boasts a large f/1.8 aperture, making it ideal for capturing stunning images with beautiful background blur.
This lens is optimized for the EOS R System, ensuring that users can achieve outstanding color balance while minimizing ghosting and flare. With its ability to deliver high-quality images in various settings, from portraits to landscapes, it stands out as an essential piece of equipment for any serious photographer.
Overview of the Sigma 18-50mm F2.8 DC DN Contemporary
The Sigma 18-50mm F2.8 DC DN Contemporary lens is a versatile option for those using Sony E-mount cameras. Retailing at $587.00, this lens provides a broader focal range compared to the Canon RF50mm. It features a constant f/2.8 aperture, ensuring consistent performance across its zoom range, which can be especially beneficial for capturing dynamic scenes.
This lens is designed with compactness and optical performance in mind, featuring superb optical quality and in-camera aberration correction. The Sigma lens is an excellent choice for photographers who value flexibility and quality without compromising on size, making it suitable for a wide range of photographic applications.
Price Comparison
When comparing prices, the Canon RF50mm F1.8 STM lens is significantly more budget-friendly at $219.00, about 63% cheaper than the Sigma 18-50mm lens, which is priced at $587.00. This substantial price difference may influence purchasing decisions, especially for those who are starting in photography or looking to expand their lens collection without breaking the bank.
While the Sigma lens offers versatile focal lengths and a constant aperture, the Canon lens provides a specialized option for low-light conditions and creative photography. For photographers who prioritize price and are content with a fixed focal length, the Canon lens presents a compelling value proposition.
Optical Performance
The optical performance of the Canon RF50mm F1.8 STM lens is particularly noteworthy, thanks to its large f/1.8 aperture, which excels in low-light situations. This lens incorporates advanced optical coatings to reduce ghosting and flare, ensuring high-quality images with impressive color balance. The PMo aspherical lens design also helps to suppress aberrations, enhancing overall image clarity.
In contrast, the Sigma 18-50mm F2.8 DC DN Contemporary lens is designed to deliver superb optical quality across its zoom range. The f/2.8 aperture ensures consistent brightness, making it a versatile choice for different shooting conditions. While both lenses offer excellent optical performance, the choice between them hinges on whether a photographer prefers the fixed aperture of the Sigma or the low-light capabilities of the Canon.
Use Cases
The Canon RF50mm F1.8 STM lens shines in scenarios requiring depth of field control and low-light performance, making it perfect for portrait photography and artistic shots. Its compact size allows photographers to carry it easily for spontaneous shooting, ensuring they never miss a moment.
On the other hand, the Sigma 18-50mm F2.8 DC DN Contemporary lens provides versatility with its zoom capabilities, making it ideal for a range of situations, from landscapes to street photography. Its ability to adapt to various focal lengths offers users more creative freedom when framing shots. For those who often switch between different types of photography, the Sigma provides a practical solution.
Build and Design
The Canon RF50mm F1.8 STM lens is designed to be both compact and lightweight, making it an ideal travel companion for photographers. Its sleek design complements the EOS R series cameras and contributes to a well-balanced setup. The lens also features a control ring for direct setting changes, adding convenience while shooting.
In comparison, the Sigma 18-50mm F2.8 DC DN Contemporary lens also emphasizes compactness and lightweight construction. However, its zoom functionality introduces a slightly bulkier design compared to the Canon lens. While both lenses are designed for portability, the Canon may appeal more to those who prioritize a minimalist setup without compromising on quality.
Compatibility
The Canon RF50mm F1.8 STM lens is specifically optimized for the EOS R series mirrorless cameras, which include models such as the EOS R, R5, and R6. This direct compatibility ensures seamless performance and high-quality image output tailored for these camera systems.
Conversely, the Sigma 18-50mm F2.8 DC DN Contemporary lens is designed for E-mount cameras, making it an excellent choice for Sony users. While both lenses cater to different camera systems, potential buyers should consider their existing equipment to make informed decisions about compatibility and performance.
Which should you buy?
Ultimately, the choice between the Canon RF50mm F1.8 STM lens and the Sigma 18-50mm F2.8 DC DN Contemporary lens largely depends on the photographer's needs and budget. The Canon lens is about 63% cheaper and excels in low-light conditions with its f/1.8 aperture, making it a fantastic option for portrait and creative photography. In contrast, the Sigma lens offers versatility and a broader focal range, ideal for those who prefer a zoom lens for various shooting scenarios.
For photographers using EOS R series cameras, the Canon lens is a compelling choice due to its affordability and optical performance. However, for Sony E-mount users looking for flexibility and consistent performance across different focal lengths, the Sigma lens is the way to go.

