This is not about focus algorithms based on AI. This is about why it can be worth to pay more for fast lens, despite the fact that they are very expensive. Some time ago fast lenses were needed to deliver image in very bad light conditions, and still are used to provide nice bokeh. With lens Optical Image Stabilisation (OIS/IS) slow shutter can help, so if bokeh is not important you can save huge money buying lens with F2.8 or even F4.0.
As such bokeh is a matter of taste and can make a photo prettier (subjectively, but usually it does). And, having choice of a lens with OIS and a fast lens without OIS, I would choose the first one, assuming it is at least F2.8. But, I have recently realised that bokeh could be useful for totally different reason than only providing beautification.
Imagine, that you make photos on the street. Even if this is about fashion or portrait photography it is good to have some background as a kind of context, anyway, the background will be there. And the background can be a serious problem. Nature photos — trees, squirrels and such — not a problem, nobody can recognise a squirrel living in his/her garden, so owner permission is not needed. But, if what you have in your background is some very specific, location related object, characteristic — again — location related patterns, colours, buildings etc. you can face serious problems if your photo, for whatever reason, becomes very popular.
In filmmaking, reading a script, first I try to find approximate cost. To get it, I look at first into location specs. Equipment, script, sound, cinematography and equipment costs are secondary, anyway for most independent productions. The most expensive stuff can be, usually, location. Basically, every location, at least in the United Kingdom, every inch of ground has some owner — be it a private owner, a community or an institution, there is always some owner. And the owner, usually, needs more money. For this reason filming on a location without proper permission can be a professional suicide, but it is also not honest — you use somebody’s stuff for professional purposes without owner permission. It doesn’t sound good. But, even if you use photo made on a location for personal purposes, and it becomes popular, you still can face serious problems.
Now, for photography, having fast lens, let’s say for full frame F1.4 and faster, you can blur background enough that it becomes not recognisable. I mean, it becomes impossible to recognise the location. After all, what you photograph is not location as such, but a person, in general — a different object, and the blurred background is there because this is how optics works. Sometimes it adds to composition, sometimes not. However, for location owner’s lawyers it doesn’t matter. What matters to them is, that you were at the location and produced photos without owner permission.
This can be a grey zone in terms of law regulations, because, this way or another, you are physically on a location and what you produce may be, or may be not, used professionally. So, in theory, if, for professional purposes, you photograph sky, zenith, without any part of location being visible, you still need proper location release form.
What I want to say is, that you should always have location release form where and when needed. And, I want to point at not that obvious fact, that if you use fast lens, which makes background sufficiently blurred and location not recognisable, it can save you huge legal headache, legal cost and legal mess. Even if the photo you make will be popular, it doesn’t mean will earn money. And even if you use photo for personal purposes and doesn’t mean you cannot be sued by location owner.
Google photographed much of Earth surface, and there are applications, based on AI, and used by some location owners like, for instance, National Parks, landmarks owners, which can can recognise where a photo was made. The effectiveness of such recognising service can vary depending on specific location and photo, but it works, limited by mathematics only. This is not about guessing, this is about image recognition, about photo geolocation, finding where a photo was made, based on maths, laws of physics and neural networks / Artificial Intelligence algorithms.
In my opinion, even if you are at some popular location, but make photos for personal purposes, fast lens can provide an extra layer of legal protection. After all, most photos ends up in Instagram or Facebook — social networks heavily scanned by many companies.
