exposure

In photo tech the class it was about exposure and if you changed the f-number or shutter speed, then the exposure would remain the same if they are both changed.

So if had 400 ISO f22 and 1/125^th

(Can only shot at 500^th)

The new exposure would be

100 ISO f5.6 and 1/500^th

(The class was the 1/3/10)