>>4448195Equivalence. If you want to get the same picture on 4/3 as you'd get on FF, knowing the crop factor is 2 (diagonal, if you want to split hairs then it's not), you halve the focal length and aperture from FF and divide the ISO by 4 (2 squared). Shutter speed remains the same. Then you get the same picture, save for aspect ratio and possibly megapixels.
