Question: I've been looking at how we've been using tags for things that are brand-specific. In my mind the vast majority of our tags should be generic, with specific brand names only used where specified in the question. I've, for example, re-tagged [this](https://photo.stackexchange.com/questions/840/dx-or-fx-lenses) and [this](https://photo.stackexchange.com/questions/380/what-is-the-difference-between-ef-and-ef-s-lenses) question so they are no longer tagged `[dx]` `[fx]` and `[ef]` `[ef-s]` but `[cropped-sensor]` and `[full-frame]` as the answers given discuss the differences between full frame and cropped sensor lens mounts, and are not specific to one particular brands mount or the other. This also means that [searching for either of the tags](https://photo.stackexchange.com/questions/tagged/cropped-sensor) reveals a list of similar answers, that are not brand specific. Obviously there will be questions that are specific to one brand or the other, but I feel we need to use the most general tag we can, so that questions are related across brands.

I don't think we need to include a list of brand names when we tag a question. Examples of this are these questions ([1](https://photo.stackexchange.com/questions/762/which-cameras-support-dng-natively), [2](https://photo.stackexchange.com/questions/759/what-are-the-advantages-of-shooting-in-a-proprietary-raw-format-over-dng)) about raw file formats that list tags for all the main formats. What do we do when a new raw format comes along? I suggest a re-tag to just `[raw]` and `[dng]` in the cases I've just linked to.

Answer: 
Agreed. Tags should cover generic ideas. Search already takes care about specific terms.
I think this can be helpful, but needs to be done quite carefully. 

For example, questions about EF/EF-S mount lenses can't *necessarily* be made generic to full/crop-sensor questions. The EF-S mount has physical differences to the EF mount that make them incompatible in one direction: EF-S lenses may damage EF-mount cameras. In contrast, the only difference in Nikon FX/DX lenses is the size of the image circle; physically, the lenses are compatible. Giving a "genericised" answer from one brand to a user of the other brand is unhelpful at best, and might break someone's camera at worst!

A further (hypothetical) example would be an "LTM" tag for Leica Thread Mount lenses; this seems highly brand-specific at first glance, but in practice covers decades of lenses and cameras from a number of manufacturers, and is a widely-accepted generic term in the community.