Bon, je savais qu'il n'y avait pas de filtre interne, donc pas d'arnaque du tout, j'ai simplement decide de le prendre quand meme.
Je me pose toutefois la question de l'utilite ou non de ce filtre sachant que j'ai lu:
"A 2mm optical glass filter with an index of refraction of 1.5 has an effective thickness of 2mm/1.5 = 1.33mm. 2mm of air has a thickness, obviously, of 2mm. The difference is 0.67mm.
The 300mm AF has an effective focusing throw of 33mm (300mm - 1/(1/3000mm-1/300mm)). You will not notice a change of 0.67mm in a 33mm range. The lens even focuses far enough past infinity so you still retain infinity focus. The focus scale will b e a few percent off. There will be no change in image quality, whatsoever.
The long lenses with drop in filters are not like the really old Nikon wide angles and fisheyes with rear screw on glass filters. In those lenses, focus throw often was only 1 or 2 mm, and a 0.67mm change was enough to destroy performance. That's what started the whole "don't run without the required filter" bit, but it doesn't apply to teles".
En d'autres termes la presence ou absence de ce filtre ne devrait en rien changer la qualite d'image sur ce type de longue focale.
Ceci dit, si vous savez ou je peux m'en procurer un merci de me le faire savoir.