Lenses

[ebiggs1]

You are correct, sir. Sorry, got my fingers typing before my brain was turned on!

The f-ratio is fixed. There that is better. It doesn't change, get slower, as you zoom.

The 17-40mm f4 does keep it's shape, length, as it zooms and I was thinking of it earlier.

[trulandphoto Frequent Contributor]

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@ebiggs1 wrote:

You are correct, sir. Sorry, got my fingers typing before my brain was turned on!

The f-ratio is fixed. There that is better. It doesn't change, get slower, as you zoom.

The 17-40mm f4 does keep it's shape, length, as it zooms and I was thinking of it earlier.

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These lenses also don't extend as they focus which some of the other lenses do. 

Technically, the 17-40 does extend and contract as it zooms it just does it inside the filter thread. So if you've got a filter on it looks like it's internal movement. The front element, however, does move. A nitpicky distinction to be sure.