>>4258018It's like this
>>4258012 with 2 stops of aperture, not 4, retard. 2 stops of aperture give 4x the light, thus 2 stops of ISO noise, and another 2 stops of ISO from adjusting exposure down, so 4 in total.
In practice, even under ideal conditions, only one stop down is needed for noise parity, in your example would mean stopping down to f/4.0 and dropping ISO by one stop.
Or I can get a speedbooster with $100 dslr lenses and BTFO every foolframe on the market.