80% of the film I've shot during my 42 years as a commercial photographer has been transparency film starting with various Kodachrome's, E3, E4 and now E6. In the earlier years it was all Kodak film and in later years I had a choice of Agfa and Fuji. Each film has it characteristics with each type such asKodachrome II, 25, X, Echtachrome commercial, X, High speed, EPP, EPY, EPR, E100 G, E100 GX, Astia, Provia, Velvia having distinct qualities unique to that particular type of film. Some are neutral, some cooler, some tungsten and some warmer plus some are pastel like E3 Commercial, and some contrasty and saturated like Velvia. It's less of a problem now than ten years ago but batch to batch of the same film will vary considerably. In commercial sheet film boxes a sheet of recommended filtrations and speeds at different exposure speeds was given. There are fewer variations now but but they still exist. If I were to shoot a critical job on film today I would select the film that most matches the subject and desired look and then do a series of tests. I have always tested every batch of color transparency film. I've always heard people say Kodak is blue but in t
ens of thousands of rolls and sheets I've never seen it unless the processing was out of spec. Kodak can go cool and fuji goes magenta if processing is out of whack. Blue indicated the PH of the color developer is too acid and yellow indicated too alkaline. Good labs run control strips and adjust PH and replenish properly. E6 is a critical process in that regard.
I always loved E100SW or GX for warm skin tones and E100S ,G and EPR for neutral tones. E100VS is a nice saturated film without the harsh contrast and blocked shadows of Velvia. Astia is a beautiful neutral medium contrast film that is designed for scanning. Provia is the film I use for punch and saturation with people. Velvia is too contrasty and death to light skin tones but lovely with black skin. Velvia is my least favorite of the batch. I would rather boost contrast and saturation when I scan rather than trying o tame contrast with Velvia. You can not add detail to shadows and highlights but you can easily simulate the contrast and saturation with photoshop.