Gold 100 and 200 In 120 Format

But most films now say professional. Why would anyone want to use

an unprofessional film?

Cheaper, mainly.

I am pretty sure it is non-professional that are aged, but I don't know more

details about aging and ripeness.

No, it's really the other way round.

Film emulsion ages, keeps on changing from the moment it is made. the colour balance shifts while it does.

In 'amateur' use, that gradual shift, and difference between batches of film, does not matter much. And the film is likely to be kept in suboptimal, or even adverse conditions.

In professional use, the best and consistent colour is important. And the film is at least kept refrigerated, or frozen.

So professional film is kept in the factory, and is released when it is at or very near optimal colour ('aged' until it is good). And it is used not long after purchase. Or frozen.

Amateur film is expected to have a long life between release, customer purchase and processing. So if it is aged until at its best, it will only deteriorate. So it is released long before it has aged until best.

That's one difference between professional and amateur film: you can rely on a fairly consistent colour between batches of the same type of film (because of the above).

Another one is the colour itself: professional emulsions have more neutral colour and a more accurate colour reproduction. Amateur film is made to have more saturated colour. (Though there are 'vivid colour' variants of professional emulslons too. Professionals too may like garish colours ;-) ).

No, it's really the other way round.

 

Film emulsion ages, keeps on changing from the moment it is made. the colour balance shifts while it does.

In 'amateur' use, that gradual shift, and difference between batches of film, does not matter much. And the film is likely to be kept in suboptimal, or even adverse conditions.

In professional use, the best and consistent colour is important. And the film is at least kept refrigerated, or frozen.

 

(snip)

OK, my understanding 44 years ago, when E6 was new, is that some changes happen faster at the beginning,

and then after some time, those don't change so much anymore. For slide film, there is no chance to correct

color balance later, as there is with negative film.

Now, I am not at all sure how hard it is to get consistent color balance in batches of reversal film,

and I do remember when it was desirable to get rolls from the same batch. So, non-professional

films were aged, such that they weren't changing so much. That they might still be good after a week,

or after a year. (Dates are commonly about a year later.) The manufacturer can make them, age them,

and then test them for appropriate characteristics, and know that they will stay close (enough) to that

for a year or so.

In the case of negative films, one can adjust color balance later, but not every change can be

fixed with color filters. If, for example, the contrast (gamma) of different layers changed at

different rates, that would complicate things.