There is no actual equivalent. It would be more or less a combination of exposure and contrast. The post above explains the levels control quite well. Analog photographic materials do not work quite the same way. Even more confusing, you are trying to get a positive from a negative, so some of the things you learned for exposing film are backward. Silver gelatin materials have a certain threshold exposure below which you don't get any image. In printing, you need to expose enough so that the highlight detail is properly visible. This is more or less like setting the white point in PS. Then you adjust the contrast so that you get a full range of tones from shadows through midtones to the whites. This is like setting both black point and scale. Sometimes you have to adjust exposure some more to get the balance, however. In fact, most people try to find an exposure level that pretty well covers the picture by using test strips, and then they adjust the contrast and fine tune the exposure to get a full range print.