>>3904045>why isn't this a default standard by camera manufacturers to their own rear lens mounts?It's really only useful for lenses with an extremely large or weirdly-shaped front element. And, in fact, you'll find that a lot of lens manufacturers DO give you the option of drop-in filters at the back of the lens for lenses like that.
For most lenses, though, it just makes a hell of a lot more sense to use a front filter. E.g., I can buy one 58mm circular polarizer and use it on a shitload of different lenses, but drop-in filters tend to be specific to each particular lens.
Not to mention that this system is less versatile. All it's really useful for is ND filters like the ones shown or color filters that aren't really that useful in the digital era. You couldn't use a circular polarizer with this particular setup because those squarish filters couldn't be rotated (although most lenses with drop-in filters do let you rotate the filter for exactly this reason), and you couldn't use a graduated ND filter because there's no way to adjust where the line is.
It's an imperfect solution to a minor problem that only exists with certain lenses. Adding it for all lenses just doesn't make sense.
