It can be quite complicated to remember what the equivalent focal lengths are for different lenses and camera systems. Full frame or 35mm cameras are used as a reference point when an ‘equivalent’ or ‘effective’ focal length is mentioned and crop frame is about 1.4-1.6 times that. Micro Four Thirds (MFT) is about double the full frame and so gets you closest per millimetre.

In these tables there are deliberately incorrect mathematical statements, these are to fit with common lens sizes (17mm MFT, 25mm crop, 35mm FF). This is to make it easier to pick up the right lens.

Here’s a table of what you get in equivalent focal lengths, in other words if you put a full frame lens of 35mm what is the ‘zoom’ that you have equivalent to in full frame terms.

Full frame (35mm)	Crop (avg of 1.5x)	Micro Four Thirds (2x)
12mm	18mm	24mm
16mm	24mm	32mm
24mm	36mm	48mm
35mm	53mm	70mm
40mm	60mm	80mm
50mm	75mm	100mm
60mm	90mm	120mm
85mm	128mm	170mm
100mm	150mm	200mm
150mm	225mm	300mm
200mm	300mm	400mm
300mm	450mm	300mm
400mm	600mm	800mm
500mm	750mm	1000mm
600mm	900mm	1200mm
800mm	1200mm	1600mm

Now a different table that’s just the same. If you want a specific angle of view what is the right lens for each format? A 12mm MFT lens will be about the same as an 18mm crop or 24mm full frame.

MFT Lens	Crop Lens	Full frame lens
12mm	18mm	24mm
17mm	25mm	35mm
25mm	35mm	50mm
35mm	50mm	70mm
40mm	60mm	80mm
50mm	75mm	100mm
60mm	90mm	120mm
85mm	128mm	170mm
100mm	150mm	200mm
150mm	225mm	300mm
200mm	300mm	400mm
300mm	450mm	300mm
400mm	600mm	800mm
500mm	750mm	1000mm
600mm	900mm	1200mm
800mm	1200mm	1600mm

Hopefully that was useful, it does answer many questions I’ve been asked about ‘those numbers and those other numbers’.