Monday 3 August 2009

Front filter for big lenses?

We spend a fortune to get a big lens-300mm+ yet we cant get a protection filter to fit on the front why? well firstly they would be huge and secondly most big lenses have one already built in-yes that right, The front glass on big lenses is a protective filter pure and simple and not part of the actual focusing/image quality glass, Look at this diagram of a Canon 600F4

Note that the front element is a flat piece of glass but all the others are curved, Now i am not saying that its not an optically perfect piece of glass as it would be on a quality filter for a smaller lens,all i am saying is that the only part it plays is to protect the inner lens elements and thats the reason we cant fit other filters to the front and filters are generally drop in's, Check out the block diagrams for your lens to see if yours has a filter built in-i believe even Canons 300mmF4 has


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