SUMMARY
Christopher Frost re-evaluated the Canon EF 40mm f/2.8 STM pancake lens on modern mirrorless bodies, specifically the Canon EOS R5 and R7. On the R5, the lens exhibits strong center sharpness at f/2.8, with corners improving significantly by f/5.6. The APS-C R7 shows good center sharpness from f/2.8, with corners resolving well at f/5.6 or f/8. While autofocus is slow and audible, especially for video, the lens offers pleasant bokeh and a useful 40mm focal length for everyday shooting.
TAKEAWAYS
Canon EF 40mm f/2.8 STM lens shows strong center sharpness on Canon EOS R5.
Corner sharpness on R5 improves to excellent by f/5.6.
Autofocus is slow and audible, making it less suitable for fast-paced photography or video.
The lens is a cost-effective option for general use when adapted to mirrorless bodies.