Strange enough I never came them across loose (in rummage box etc.) only two or three mounted on lens. And I found their designation enigmatic.
Even more strange, I did not find them covered in Canon literature and broshures. Only within lens listings.
Here is what I made out of their coding:
First Type
1.) B [I guess "Bayonet"]
2.) 2 figures [filter-thread diameter as corresponding to bayonet size]
3.) W , S or T [Wide-angle- , Standard- or Tele-lens]
4.) A , B or C [at B 52 hoods: Focal lenght: 35 , 28 or 24mm resp.]
Second Type
1.) W [I guess "Wide-angle zoom"]
2.) 2 figures [front-barrel diameter]
3.) B [at one model: 35mm min. focal length]
Third Type
1.) EH [Extension Hood, to be put on built-in hood]
2.) 3 figures [diameter of built-in hood in mm it seems]
Even more strange, I did not find them covered in Canon literature and broshures. Only within lens listings.
Here is what I made out of their coding:
First Type
1.) B [I guess "Bayonet"]
2.) 2 figures [filter-thread diameter as corresponding to bayonet size]
3.) W , S or T [Wide-angle- , Standard- or Tele-lens]
4.) A , B or C [at B 52 hoods: Focal lenght: 35 , 28 or 24mm resp.]
Second Type
1.) W [I guess "Wide-angle zoom"]
2.) 2 figures [front-barrel diameter]
3.) B [at one model: 35mm min. focal length]
Third Type
1.) EH [Extension Hood, to be put on built-in hood]
2.) 3 figures [diameter of built-in hood in mm it seems]