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Old Jan 25, 2006, 4:46 AM   #1
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This question gets asked occasionally, so here's the answer

Needless to say, this tells you nothing about how close each lens will focus, or which one will be brighter (fastter), since those are dependent on the unique design of each lens.

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Old Jan 25, 2006, 8:26 AM   #2
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This one should be sticky thread...
There's so much confusion and delusions around this.

Instead of biggest zoom number most important thing should be smallest and largest focal lengths because those are that which decides to what kind of photography camera fits.
As example these media sexy much touted ultrazooms all have lousy wide angle (shortest focal length is high) while that long 380mm to 430mm tele benefits mostly just wild animal/bird photography and about 200mm is quite enough for general photography.

For visualizing significance of focal lengths here's shot taken with 28mm+0.8x wide angle converter meaning ~22.5mm focal length:

For getting 38mm (common "wide" angle of dozenware/ultrazoom cameras) field of view crop away slightly over one third (1/3rd) from height and width which means loosing over half of image's area.
For comparison FOV of 28mm lens is slightly over one sixth (1/6th) narrower and lower.

And then for differences in tele meaning that longer focal length. (hopefully told in ads)
So for example let's compare difference between 200mm and 400mm.
While I don't have such photo at the hand you can imagine that previous shot as taken at 200mm. Now for visualizing how much smaller area 400mm would magnify to fill the frame halve that photo in horizontal and vertical direction, area of one resulting "one fourth" tile is what would fill the frame with 400mm lens.
This ratio stays same everytime when focal length is doubled (when increasing focal length) or halved. (when going towards smaller focal lengths)
So 200mm magnifies equally much more when compared to 100mm as 400mm when compared to 200mm.

So the longer the focal length the more insignifact absolute mm difference becomes. Difference of even 50mm isn't much anything when talking about few hundred millimeter long focal lengths while only 10mm difference has huge effect in wide angle end.

And then to biggest scam of digital photography (and favorite tool of marketers selling low quality sh*t) called as Digital zoom, which is nothing more than pure fraud.
For example 2x digital zoom does nothing else than crops that one fourth area from center of frame, while field of view is now similar to lens with double focal length the fact is that there's equally small/much details than without this 2x digital zoom.
But just taking this low resolution snapshot from center of frame would be too obvious for pushing it down from the throats of sheeps in butcher's row so to cover this fraud they often resize result of cropping to original resolution.
Now this one is similar to just going closer and closer to TV when you already see grains/pixels so it shouldn't be hard to realise that anyone selling cameras basing to digital zoom should be convicted&punished from fraud.
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