Quote Originally Posted by bdial View Post
It sounds like you are speaking of "exposure" in terms of the amount of light the subject is exposed to, where in still photography, most of us think of exposure in terms of the amount of light allowed to strike the film.

Still photographers have a lot of flexibility in adapting to the light hitting the subject, we have both duration of exposure (to the film/sensor) and intensity to work with. OTH, cinema photographers have a fixed shutter speed, and so control exposure by the amount of light placed on the subject, which is why even when shooting in daylight they have truckloads of lights, reflectors, and shading panels to exercise that control.

In both cases, the ISO of the film is a "tweak", that is, we can choose a faster or slower film, which then influences the other choices. A faster film will allow the use of small lens apertures, or shorter shutter speeds, to yield increased depth of field or reduced movement blurring, for example.

Does this address the point you are making?
No, not my point, nor I think Chan's.

I think both of us are assuming that the scene EV would be the same for any specific comparison.

I think Chan is suggesting that in the digital realm the ISO setting is not necessarily considered a tweak, that it has become a primary adjustment that can be used in place of/instead of time and aperture.

I'm suggesting that we can do essentially the same thing with film, as long as we consider the adjustments that can be made in the darkroom.

XP2 is a great example, the following was copied from the Ilford spec sheet:

Best overall quality EI 400/27
Finer grain (with easy printing) EI 200/24
Finest grain (but with denser negatives) EI 50/18

No matter which film speed is chosen, standard C41 processing is recommended.
In this example essentially only the exposure of the paper need be adjusted and the ISO/EI can be allowed vary from frame to frame. Using ISO/EI as a primary adjustment allows a very different way of shooting than Adams used and taught. Yes the technical look of the print may change with the change in exposure but, the creative use; the ability to maintain a given DOF and given amount of motion blur across a range of EV's is very freeing.

This same principle (ISO/EI being adjusted) is used in disposable cameras, Holga's, blah, blah, blah...

In my experience normal B&W films can be used the same way.