When I shoot in RAW, and don't fix exposure (either by locking exposure in (semi-)automatic modes or by switching to manual mode, I have a hard time matching exposures when the meter adjusts shooting parameters due to changes irrelevant to me (e.g. a bright spot appearing in the background should not change the exposure of the main subject). I've created this calculator to help me match exposures. Just fill in details of both shots, specify the exposure correction you used in your RAW developer for the first one, and it'll calculate the value required to match the exposure of the 2nd shot to the 1st. Note: some fields are read-only as they contain calculated data (area = aperture2, amplification = 2exposure correction, effective ISO = ISO * amplification, effective exposure = area * effective ISO * shutter, required exposure correction = log2(amplification)).