Why does it matter...an explanation.
Why does it matter...an explanation.
If you are a professional and you are shooting a large job, lets say a multi-page catalog shoot with hundreds or thousands of transparencies. You want the first shot to be the same color balance as the last shot. Clients are very particular about the color rendition of the photos of their products. The photo needs to look exactly like the product.
OK, so you shoot a few tests, have them processed, evaluate the transparencies on the light table, and possibly make corrections in your lighting to achieve a very neutral lighting scheme to accurately depict the clients products. You purchase enough professional film from the same emulsion lot (as indicated on the film box), to do the job, and once done, all the images should match for color.
If you purchased amateur film, there would be variances in the neutral balance of the images from roll to roll. Perhaps not enough to notice on the average street photography or scenics, but when you shoot in a studio with controlled lighting, you would notice a difference between shots from different rolls.