10-14-2013 08:45 PM
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.
10-15-2013 06:38 AM
@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.
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.
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