What is grain?

[Kit_Taylor]

What is it that happens to film prints to make them grainy?

[utero]

it depends on the film stock, developmnt process, length of time sitting in a can. For instance the grain in three kings is intentional with a certain film stock and film processing techinque. It also depends on the original format, for instance a 16mm negative blown up for 35mm viewing will have grain it.

[Kit_Taylor]

Yes, but what phsyically happened to the film stock to make it grainy? Mould, a bit of water vapour, dust, wear and tear?

[utero]

general aging, poor storage, restoration, transfer.........

[Kit_Taylor]

Yes, but specifically, like in chemistry A-level terms?

:)

[macmatt]

All film has grain - that's what makes the picture, it's nothing to do with poor storage or mistakes. Digital pictures are made up of pixels, images on film are made up of grain! The grain in some film stock is larger and therefore more visible to the naked eye - generally the faster the film stock, the larger the grain.

As for A-level Chemistry, I never did it, but an explaination of grain should be easily found in any basic photography book. Did Janet and John ever do Photography?:D

[dangermouse]

Now this is where DVD audio commentaries come in handy - if I remember rightly the techniques applied to the negative in both Three Kings + Seven (amongst others) are explained on the audio coms for those movies.

I think most commonly movies like Traffic were shot on 16mm film stock, which when blown up and projected are naturally visibly grainy. (most movies are shot on 35mm)

Also other techniques used - like the treatment of the negative on Three Kings, under go somthing called Bleach Bypass, whereby (and someone may have to correct me on this) the process of passing the film stock through different chemical washes to even out the colours etc involves a stage where all the silver is removed.

By skipping this process it leaves the film with that silvery look which is pretty cool.

But just talking about grain - like Macmatt mentioned above - film has grain naturally. It just depends on what speed you run the film at as to wether it shows up more.

[john316]

Saving Private Ryan underwent a very similar procedure to obtain its distinctive look.

[Michael Brooke]

Macmatt and Dangermouse are absolutely right - <U>all</U> photographic film is made up of tiny particles, but there's a huge difference in their size between, say, 25ASA Kodachrome (where you really do have to blow them up to giant size to see any grain) or a high-speed 1600ASA stock which can resolve images in minimal light, but which will inevitably look grainy as hell.

Also bear in mind that the size of the negative plays an important role too - Super 8 will be as grainy as hell regardless of how you watch it, 16mm is usually pretty grainy (though a good DVD transfer can minimise this) while anyone who's seen <I>Lawrence of Arabia</I> in 70mm will have seen a picture so sharp and clear that Anthony Quinn's false nose looked almost three-dimensional. And of course IMAX offers a sharper picture still.

You can get a picture that, to the naked eye watching it on a normal-sized screen, is effectively grain-free, but it demands relatively insensitive film (the smaller the particles, or grain, the more light is needed) and powerful lighting, so it's not really conducive to short production schedules and guerrilla-style film-making. That's why independent films often look grainier than big-budget mainstream ones, and why the latter often exaggerate the grain in order to look more "independent" - <I>Traffic</I> and <I>Three Kings</I> being good examples.

[Bamse]

Does having a 100-hertz T.V help reduce the visible grain in the picture?

[Brian F]

I doubt very much if 100hz TV would have any affect on the appearance of grain.
Another point is that grain builds up the more generations you are from the original camera negative. It was common a while ago one element in a blue screen shot to have much more grain than the other. Digital compositing (and improved internagative film stock)has evened this out.
Super8 as grainy as hell? Well 160ASA Ektachrome maybe, but having seen Kodachrome40 camera originals and commercial releases (printed from 16mm internegs onto Agfa print stock) on screens up to 24ft wide that looked less grainy than the 70mm prints of "A Star is Born" 1976, I'd have to disagree there.
P.S. 16mm concert footage blown up to 70mm (cropped to fit) really looks bad, I believe Concert for Bangladesh was the only one and only done to get 6 track stereo sound.