carllooper wrote:Film is now a lot more about film acquisition and digital post. I remember the time when the lattitude of film was regarded as about 3 stops! Why? It wasn't really the film stock (although advances have been made). It was because there weren't the tools we now have, to even think about film in terms of anything beyond 3 stops.
This is erroneous. I've conflated two things here. My apologies. There is a difference between latitude (exposure latitude) and dynamic range. Film still has a small exposure latitude (of a few stops). As does digital. Exposure latitude is not the same thing as dynamic range. The extent to which you can vary the exposure (of film or digital) and still obtain a good range in the result is the exposure latitude. The range, on the other hand, is the range of the result, which is many more stops.
When talking of depth we're talking of dynamic range rather than latitude. When we say film has greater depth we're assuming a level playing field we're both film and digital have been optimally exposed, ie. for the greatest possible range.
Latitude is really about how accurate (or lazy) you need to be (or can be) during photography. If a film stock has a latitude of 3 stops (for example) you can get away with being out by a stop or two during photography and still obtain a reasonable range in the result. If the range of film is better than digital (as it seems to be) it also means the latitude of film must be better than digital. So in some contexts latitude and range are interchangeable.
Perhaps what I should have said, is that prior to the digital age, exposure latitude was more important information than dynamic range. Film just had the range it had. Exposure latitude was something you needed to know in order to determine how accurate you should be with your exposure. With the advent of digital post the dynamic range of film became something equally important. How many bits were required to capture the range of film?
The current standard is 14 bits, based on the assumption of a 13 stop range. 13 bits are required to capture 13 stops. The extra bit is to resolve any ambiguity.
However the dynamic range of film is not necessarily 13 stops. It could very well be many more stops. The measurement of range is limited to where you draw the line between noise/grain and the signal. But this dividing line remains the subject of ongoing research. We see noise/grain removal algorithms getting better each year. Why? Because insights regarding the properties of noise/grain is not yet complete. And we don't really know if it ever can be. It is an ongoing research area. Surprising results have been occuring for decades now. What was seemingly impossible one year becomes possible the next.
From a digital perspective, film (or analog systems in general) are quite strange in this respect. They have a range which is not defined in advance. Rather they have a range defined by the properties belonging to the materials used. Digital systems are defined in terms that are independant of the materials used. Certainly the properties of materials play a part, but those properties are kept at a distance. For a given digital system you can swap the materials/properties without necessarily changing the digital attributes of the system.
A digital image can be stored by writing down, on a peice of paper, all of the numbers for each pixel. It might take a while but it can be done. The information is independant of the medium.
You can't store all the information in a film image that way. The "information" in a film image is quasi-infinite.
