Quote Originally Posted by ic-racer View Post
Yes, in Jones et al they demonstrated a plateau in picture quality with increasing exposure when negatives are used for contact prints. However, smaller negatives that would be used for enlarged prints, there was usually an optimum exposure. This is because the film tends to lose resolution as silver density builds up. Though, you could consider it a plateau with a peak value.
I do agree that there're limits and that staying within a tested range is important to get decent quality.

I also believe that it's not the same for everybody, it's highly dependent upon the subject matter in question. Those for whom high detail in both shadow and highlight is important, have a much smaller range to play in, than those of us that are just worried about landing the mid tones.

As with everything photographic, there are trade-offs. For me, and my subjects, allowing the EI to float is a way of making shooting simpler and even getting people to take the camera less seriously (say with a Holga, disposable, or 35mm P&S instead of an F5). It's also a way to focus more on content and timing and worry less about the technicalities.