Why different size and wt for the same range of lenses?

[code]

Hi guys

Was just wondering for the same range of lenses of different make (eg Canon 24-70 f/2.8, Tamron 28-75 f/2.8, Sigma 24-70 f/2.8), why are the filter size, weight, etc different despite having the same f stop?

Was thinking of bring one of these lens for travelling and now, the Tamron lens seems to win hands down in terms of weight and size.

 

[theITguy]

They can always make the filter size bigger (why I dunno maybe to reduce vignetting). Also the design of the lens (Tamron here) which can give a small filter size. I also dun understand why since I am not an engineer and I dun really care.

Not all lens are what they are listed (for example a 300mm prime may be only 295mm as there are some allowance of 5% tolerance in difference).

 

[Ian]

Hi guys

Was just wondering for the same range of lenses of different make (eg Canon 24-70 f/2.8, Tamron 28-75 f/2.8, Sigma 24-70 f/2.8), why are the filter size, weight, etc different despite having the same f stop?

Was thinking of bring one of these lens for travelling and now, the Tamron lens seems to win hands down in terms of weight and size.

The reasons for the differences are many, however here's a few of them:

* Different optical designs between lenses from different manufacturers.
* Different materials used internally and externally by different manufacturers
* Different glass used in the lenses from different manufacturers

Get the idea? Each manufacturer has their own set of design criteria (optical performance, weight, physical size, durability, cost etc) and achieves the design goals in their own way. There are however marked differences in the lenses, not just in size and cost, but also in optical performance for example.

Ian

 

[foxtwo]

... (eg Canon 24-70 f/2.8, ..., Sigma 24-70 f/2.8)...

Probably because they use different design & technology to make their compound lenses. Else what's the difference in purchasing Canon over Sigma if they are the same everything except price?