M43 → Full Frame Converter
Enter your M43 focal length and aperture to see full-frame equivalents. Two different "equivalences" are explained below.
FF equivalent focal length
× 2 crop factor
DOF equivalent aperture
× 2 (same depth of field on FF)
Light equivalent aperture
× √2 ≈ 1.4 (same exposure on FF)
M43 aperture (your input)
DOF equivalence (×2): to get the same angle of view and the same depth of field on full frame, you need to open up two stops. An M43 f/1.2 is equivalent to FF f/2.4 for depth of field.
Light equivalence (×√2): the sensor area difference between M43 and FF is ×4, but the f-stop system already accounts for the same exposure per unit area. To match total light gathered (relevant for noise), you need ×√2 ≈ 1.4 stops. so M43 f/1.2 gathers the same total light as FF f/1.7.
These are different questions. photographers often confuse them.
The 2x crop factor
Micro Four Thirds sensors measure approximately 17.3mm × 13mm. A full-frame sensor measures 36mm × 24mm. The diagonal ratio between the two is approximately 2:1, which is why M43 is called a 2x crop format.
For angle of view, this is straightforward. A 25mm lens on M43 gives the same angle of view as a 50mm lens on full frame. Multiply your M43 focal length by 2 to get the equivalent full-frame focal length.
Two types of equivalence
Focal length equivalence is simple. Aperture equivalence is more complicated because there are two different things aperture affects: depth of field and light gathering. They follow different multipliers.
Depth of field equivalence
Depth of field is determined by the physical size of the entrance pupil, not the f-number. The entrance pupil is focal length divided by f-number. To get the same depth of field on full frame as you get on M43, you need to open up by 2 stops. An M43 f/1.2 gives the same depth of field as a full-frame f/2.4 lens.
This is the equivalence most relevant to portrait and subject isolation work. If you are trying to replicate a specific look, use the DOF column from the calculator above.
Light equivalence
The f-stop system is defined so that the same f-number gives the same exposure per unit area regardless of sensor size. That means f/1.2 on M43 and f/1.2 on full frame give the same exposure in the same light. No conversion needed for exposure.
What differs is total light gathered. A full-frame sensor has roughly 4x the area of an M43 sensor, which means it collects more total photons at any given f-number. This affects noise, dynamic range, and the signal-to-noise ratio, not exposure. To match total light gathered, multiply by the square root of the sensor area ratio (approximately √2 ≈ 1.4). So M43 f/1.2 gathers the same total light as FF f/1.7.
Which one matters for you?
For most photography decisions, the DOF equivalence is what matters. If you are deciding between lenses or comparing M43 gear to full-frame reviews, use the DOF column.
The light equivalence matters when evaluating high-ISO noise comparisons between formats. Review sites that compare M43 and FF noise at the same f-number are not making a fair comparison from a total-light perspective. Adjusting by √2 gives a fairer basis.