Difference in same name film but different speeds

This may be a silly question but here goes:

Am I correct in thinking that the main difference between films of different speeds but the same brand/type is just grain size.

Examples would be the Delta and Tmax ranges. They are available in 100, 400 & 3200 speeds. Would the main difference only be in the grain size or would there be other obvious differences?

So if I try Delta 400 and like the tones and contast but not the grain, I can switch to Delta 100 for finer grain but same tones and contrast?

Peter

You are correct that higher speed films do exhibit larger grain. That is not the only difference, however. Different speed films exhibit different characteristics insofar as their H&D curve. This is true not only within broad classifications of film speeds but also within the same speed films between different manufacturers.

Thanks Donald,

I just thought that films of the same name (i.e. Delta 100, 400 etc) would produce similar results except for grain, if not shot in extreme conditions.

Peter

There are certain similarities, but really they are not as consistent in appearance and the branding would lead one to believe. Best just to test them out and see what you like. Among the modern films, I prefer TMX to Delta 100, but I prefer Delta 400 to TMY.

Thanks David, I will continue testing.

Peter