Switching camera systems means re-learning your focal lengths, because the same lens frames differently on each sensor size. This tool shows the full-frame equivalent of any lens and the native focal length you would need on every other format to keep the same framing.
How it works
The full-frame equivalent normalises the field of view across formats:
equivalent focal length = native focal length × crop factor
The crop factor is the ratio of the full-frame sensor diagonal to the format’s diagonal — 1.5× for most APS-C, 2.0× for Micro Four Thirds, 0.79× for 44×33 medium format. To find the native focal length on another format that matches the same framing:
native (other format) = equivalent ÷ crop factor of that format
The table also reports the horizontal angle of view, computed from the focal length and sensor width:
angle of view = 2 × arctan(sensor width ÷ (2 × focal length))
Worked example
A 50 mm lens on full-frame has a crop factor of 1.0, so its equivalent is 50 mm with roughly a 40°
horizontal angle of view. To match that framing:
- APS-C (1.5×): 50 ÷ 1.5 ≈ 33 mm native
- Micro Four Thirds (2.0×): 50 ÷ 2.0 = 25 mm native
- Medium format (0.79×): 50 ÷ 0.79 ≈ 63 mm native
All four lenses give the same field of view despite very different focal lengths.
Sensor formats and their crop factors
| Format | Crop factor | Sensor diagonal (approx.) | Example systems |
|---|---|---|---|
| 44×33 medium format | 0.79× | ~55 mm | Fujifilm GFX, Hasselblad X |
| Full-frame (35 mm) | 1.0× | 43.3 mm | Sony A7, Nikon Z6, Canon R6 |
| APS-H | 1.29× | ~33.5 mm | Canon 1D (older) |
| APS-C (Nikon, Sony, Fuji) | 1.5× | ~28.9 mm | Fujifilm X, Sony A6xxx, Nikon Z50 |
| APS-C (Canon) | 1.6× | ~27 mm | Canon EOS M, Canon R50 |
| Micro Four Thirds | 2.0× | ~21.6 mm | Olympus/OM System, Panasonic G |
| 1-inch type | 2.7× | ~15.9 mm | Sony RX100, Nikon 1 (discontinued) |
What equivalence does not cover
Crop factor describes framing — how wide or narrow the field of view is. It does not describe everything about the image a lens-sensor combination produces.
Depth of field. Two lenses with the same equivalent focal length and the same equivalent aperture produce similar blur only if the apertures are chosen to match. For example, a 50mm f/1.8 on full-frame produces shallower background blur than a 25mm f/1.8 on Micro Four Thirds even though both frame a scene the same way. To match the depth of field as well as the framing, you would need a 25mm f/0.9 on MFT — an aperture that is rare and expensive.
Total light gathered (photons per image). A larger sensor gathers more light for the same subject and framing, which affects noise performance in low light even when exposure brightness (f-number and shutter speed) is equal. This is the physical reason why full-frame sensors tend to produce cleaner high-ISO images than smaller sensors, independently of pixel count.
Diffraction limit. Smaller sensors tend to diffract at wider apertures because the same f-stop corresponds to a smaller physical aperture opening. MFT shooters often see diffraction softness beginning around f/8, while full-frame can stay sharp through f/11 or f/16.
Tips and notes
- The number engraved on a lens never changes — only the sensor’s crop of the image circle does.
- Equivalent focal length matches framing only; depth of field and total light gathered still differ between formats.
- A smaller sensor at the same equivalent framing and aperture renders more depth of field, so background blur shrinks even when exposure stays the same.
- When a manufacturer markets a lens as “equivalent to X mm full-frame” they are quoting the cropped field of view — not a physical change to the lens optics.
- All maths runs locally in your browser; nothing about your gear is uploaded.