An exposure index of about 0.5-1EV over the ISO rating is usually possible.
The film allowed Correll latitude in choosing a broad range of exposure indexes.
When a film's effective sensitivity has been varied, the resulting sensitivity is called the exposure index; the film's speed remains at the manufacturer's indication.
A spokesman said EI, or exposure index, was a measurement of film sensitivity.
The exposure index may simply be called the speed setting, as compared to the speed rating.
It didn't matter if they were famous photographers; what you wanted was their secret formula for developing Tri-X at an exposure index of 6400.
It has uses in surveillance and other work where it can be given a pushed exposure index between 1600 and 25000.
Maybe you like to exposure Kodachrome 64 at an exposure index of 80.
Cinematographers may also apply exposure compensation for changes in shutter angle or film speed (as exposure index), among other factors.
It might need filtration or a change in the exposure index before it suits your taste.