Interesting comparison I guess...

Joined
Nov 10, 2005
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3,403
Location
Merrick, NY
Same shot...

D3 and 105 VR, F2.8, ISO 800

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D2XS and 18-200mm VR shot at 70mm (equivalent to 105 in FX), ISO 500, F5 (wide open)

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Observations...

105 with the 18-200 is not really 105!!

105 VR at 2.8 blows away the 18-200 at F5.
 
Last edited by a moderator:
Joined
Jan 15, 2008
Messages
4,553
Observations...

105 with the 18-200 is not really 105!!
The 18-200 focal length shortens a lot when you focus closer. It is only about 128 mm at 200 mm setting at the minimum focus. This time your camera to subject distance was moderate though. This same focal length shortening applies to the 105/2.8 also. It is 105 mm only at infinity focus.

The focal length of a lens is always given at infinity focus and it is a conveniently rounded number, your 105 could actually be anything between 103 and 107 mm and the 18-200 might very well be 19-195 mm

Perhaps a small part of the inconsistency can be attributed to the accuracy of the printed numbers on the barrell and yet a smaller part to the actual crop factor being 1.54 not 1.5 and so on.

The image quality differences are pretty obvious to the naked eye though.
 

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