How to use it
- Pick your sensor type, or choose Custom and type the crop factor.
- Enter the focal length and the maximum aperture of the lens.
- Read the equivalent focal length and aperture on full frame.
How it works
- Equivalent focal length = focal length × crop factor
- Equivalent aperture = f-number × crop factor
- Light difference in stops = log₂(crop factor²)
Presets: full frame ×1, APS-C ×1.5 (Nikon, Sony, Fujifilm) or ×1.6 (Canon), Micro Four Thirds ×2 and 1-inch type ×2.7. These are rounded, conventional figures.
Worked example
A 35 mm f/1.8 lens on an APS-C camera with ×1.5 frames the scene like a 35 × 1.5 = 52.5 mm lens on full frame, and gives the depth of field of about f/2.7. The total light gathered by the sensor is log₂(1.5²) ≈ 1.17 stops lower than full frame at the same settings, which is why small sensors tend to be noisier at high ISO.
Tips
- Equivalent aperture describes depth of field and blur, not exposure. Your camera meter still uses the real f-number.
- Compare lenses by equivalent focal length when you switch between camera systems.