I see how some filters have to be attached to the front of the lens, because they require some amount of interaction, like a graduated neutral density or circular polariser filter.
But what about the other static1 filters? Wouldn't it be possible to have a filter thread at the back of the lens?
The disadvantage would be that one had to remove the lens in order to change the filter. The advantages would be to have smaller filter sizes or possibly only one filter size for all lenses.
Camera manufacturers solved the problem for telephoto lenses with drop-in filters instead of attaching the filter to the rear end. This makes me wonder if there's a technical reason that filters are not attached to the back end of a lens?
Is there not enough room for a filter? Is it too much development for too little gain feature wise?
The number of filters that could be added to the back is certainly limited, but so is the number that can be added to the front without getting issues like vignetting.
1 for lack of better word: those filters that don't require any interaction