We're drilling down to the essence of the difference between analogue and digital. Here's Phil Rhodes' take on this persistent question. It's a fascinating read, and is pretty definitive on the subject
I write hoping that the subject of this article – the move from film to digital, as if that's a complete description of such a complex situation – is no longer controversial enough to provoke a lot of angry mailbag. Some of what's to come in this discussion of what's been lost and gained will be familiar to most people who've shot both formats, but I hope to explore one particular point that's of waning importance now but did a lot to define the debate at the beginning of the changeover, and which has left echoes that are are audible to this day. What I'm talking about here is the difference between shooting film and postproducing that film in a digital environment, and shooting digitally in the first place, a distinction which was and is frequently glossed-over in discussions of the relative merits.
The first thing to be clear about is that, despite the nostalgia, film is far from free of faults. Grain is, despite its intermittent fashionability, noise. Being a fundamentally mechanical animation system, film is subject to to instability and flicker, dirt, scratches, colour variations, and other problems, all of which are inevitably present to at least some tiny degree in all film. I'm going to overlook the corner case in which these faults are artistically sought after, as they're easy enough to simulate in either medium.
The worst of all worlds
Modern camera and handling techniques reduce the effects of these problems to low levels, but the operative point is that no matter what the problems of film may be, once we digitise film-originated footage, for all that it provides the enormous capability and flexibility of digital postproduction, we inevitably suffer the worst of both worlds: all of the problems of film, and all of the problems of digital. It's only the fact that both worlds control these problems so well that digital intermediate was ever acceptable. Even so, ultimately, when we scan film and treat it digitally, especially when we scan at 2K, it's reasonable to fear that we are often losing a noticeable amount of information.
This happens for the simple reason that digital images are made up of a grid of squares, which have almost nothing to do with grains on the film image. It's necessary to have at least several pixels per film grain to completely capture the information of the film image, although the result still won't look as sharp as if that same digital image had been filled with digitally-originated information at its Nyquist limit. This oversampling requirement is an intrinsic problem associated with the conversion of one imaging format to one that operates on a fundamentally different technology base, and means that, on top of the worst-of-both-worlds issue, scanning 35mm film is an inefficient game at best. 2K film scans are, notoriously, less sharp than 4K scans of the same material, even when the original frame doesn't appear to have 2K of information in it, for this reason.
If you originate digitally, of course, you're sidestepping grain, instability, and all the other problems, and you're likely to fill your digital images with more information than the film scanner could, pixel for pixel. It's possible to buy cameras which are quite competitive with some sorts of 35mm film for the cost of a couple of rolls of stock, not even including processing, and the idea that film can in any way be price competitive is sheer fantasy.