MatthewRoberts wrote:Sorry Gary, I mean't filter size - thanks!
Ok, cool.
For all intents and purposes, it's not going to be a factor in your shooting.
That said, the filter size is a representation of the diameter of your lens, which in turn is a reflection of some design decisions taken by your lens manufacturer.
Bear with me ... this might get a tad complex.
Those design decisions will and do have a bearing upon a number of factors within your lenses: the maximum lens aperture available (the largest size of the hole through which the light passes) bears a mathematical relationship to the focal length of the lens, and (in a nutshell) the larger the hole, the larger the diameter needs to be, for any given focal length.
Don't worry too much about it, except to understand that larger holes pass more light, thus they need more glass in their construction, which means that they weigh more, and cost more. Yep: the bigger the hole, the more you pay.
And so, getting back to your original question, rather than looking at the filter diameter (which is merely a physical property), look at the maximum aperture that the lens supports. A lower number means a larger hole and thus greater light passing, which probably means better glass. f/2.8 lets in more light than f/4, and f/1.8 lets in more light again. and so on -> f/1.8 -> f/1.4 f/1.2.
This is generally what is meant when we talk about glass being "fast": it lets in more light, thus it's more suitable for shooting in darker locales, thus it lets you shoot in more difficult circumstances. It's regarded as being fast in optical terms.
Better glass means more $$$$$ to pay!
Better glass is generally bigger, fatter, and heavier.
So, in terms of lens quality, filter size is irrelevant, but it might be an indicator to other lens properties, but those other lens properties are probably better expressed within other aspects of the lens's nomenclature.
Hopefully you're still (somewhat) with me here.
