Over the weekend I decided to do a test of three types of Nikon lenses which left me baffled as to how Nikon labels its gear. The lenses in question were the 18-200mm VR (two of them actually), 55-200mm VR and the 70-300mm VR. I'll save you the backstory of what precipitated this test but the outcome was that while both the 55-200mm and 70-300mm took the same shot at 200mm, both of the 18-200mm had a good 30-35% less zoom (about 150-160mm equivalent of the other two lenses). So AW Photography gurus, what gives here? I tried searching on the web to see if anyone else noticed something similar but came up with nothing. Is it simply down to Nikon using "200mm" as a marketing ploy or is something wrong with the equipment? I'm having a hard time believing its the latter due to the consistency of the results (i.e. both 18-200 having the same zoom and both non 18-200s having more)

You'll find this with most if not all manufacturers

BTW, instead of "less zoom", you should really say "shorter focal length". "Zoom" just means variable focal lenght, and applies to both long and short ends of a zoom lens

I assume they were all focused the same, as stills lenses often breathe quite a bit (that's the term we use in cinematography, I don't know if it has a stills equivalent - basically the image size changes with focus). We don't use stills lenses on movie cameras very often for this exact reason - racking focus looks like you are zooming. Try varying the focus and see how things change.

Measure the field of view and compare it to the expected result from the "Dimensional Field of View Calculator" on the page linked below (a little more than halfway down the page). Are the results off at both ends of the lens? Are the other lenses spot-on according to this calculator, or are they off as well?<ul><li><a href="http://www.tawbaware.com/maxlyons/calc.htm">http://www.tawbaware.com/maxlyons/calc.htm</a</li></ul>

<i>Finally, one word about focal length. As with most zooms, focus point shifts the focal length a bit. At infinity, the lens is 18mm at its wide end, and I think a few millimeters short of 200mm at the tele end (I've seen one measurement that says 193.5; all I know is that it's a bit shy of my 70-200mm at infinity). At very close focusing distances, which is where I'm at most of the time, the lens is almost down to 17mm at the wide end, with very little perceptible change at the tele end. Perfect! Just the way I want it to be.</i>

At what focusing distance are you comparing?<ul><li><a href="http://www.bythom.com/18200lens.htm#autofocus">http://www.bythom.com/18200lens.htm#autofocus</a</li></ul>

I can see small shifts of focal length but I don't think the 50mm difference I observed can be put down to focus