07-18-2010, 03:05 PM
[quote name='Brightcolours' date='18 July 2010 - 04:35 PM' timestamp='1279463757' post='1099']
The Nikon goes towards 135mm actually, depending on whichever formula one uses to calculate it.
Problem with all used formulas is that they say all Canon 70-200 lenses (and the old ones from Nikon, Pentax, Sigma, Tamron, the Sony's and so on) all reduce focal length at MFD, just not to the extent of the Nikon VRII and now the new Sigma.
But either all those formulas are inaccurate, or focal length is NOT linked to field of view.
Because, with all Canon 70-200's (both f4's and f2.8's), while according to the formulas the FL decreases, in effect the field of view gets smaller/more narrow (not only with those Canons... with all 70/80-200's I mentioned).
Puzzling!
[/quote]
The field of view is supposed to narrow when focusing closer, not because the total image circle doesn't cover the total lens AoV anymore, but because you are essentially cropping a smaller and smaller part of the image circle. At 1:1 the image circle actually is supposed to fit 4 total image sizes, while you only see the centre part of it (hence the two stop light loss at 1:1).
However, when a zoom lens suffers from breathing, the image circle doesn't get bigger as it is supposed to, when focusing closer, and hence the FL is not kept the same, resulting in the magnification also to be less than expected.
BTW, this is something that generally happens with IF prime lenses too, although with those generally careful attention is paid to magnification factor, f..e., with the Canon 100 macros, and the EF-S 60 macro. I did the calculations once, and the EF-S 60 macro becomes a 50 mm macro at 1:1, the 100 mm non-IS macro a 73 mm or 75 mm macro or thereabouts (can't remember the exact number for this one).
Kind regards, Wim
The Nikon goes towards 135mm actually, depending on whichever formula one uses to calculate it.
Problem with all used formulas is that they say all Canon 70-200 lenses (and the old ones from Nikon, Pentax, Sigma, Tamron, the Sony's and so on) all reduce focal length at MFD, just not to the extent of the Nikon VRII and now the new Sigma.
But either all those formulas are inaccurate, or focal length is NOT linked to field of view.
Because, with all Canon 70-200's (both f4's and f2.8's), while according to the formulas the FL decreases, in effect the field of view gets smaller/more narrow (not only with those Canons... with all 70/80-200's I mentioned).
Puzzling!
[/quote]
The field of view is supposed to narrow when focusing closer, not because the total image circle doesn't cover the total lens AoV anymore, but because you are essentially cropping a smaller and smaller part of the image circle. At 1:1 the image circle actually is supposed to fit 4 total image sizes, while you only see the centre part of it (hence the two stop light loss at 1:1).
However, when a zoom lens suffers from breathing, the image circle doesn't get bigger as it is supposed to, when focusing closer, and hence the FL is not kept the same, resulting in the magnification also to be less than expected.
BTW, this is something that generally happens with IF prime lenses too, although with those generally careful attention is paid to magnification factor, f..e., with the Canon 100 macros, and the EF-S 60 macro. I did the calculations once, and the EF-S 60 macro becomes a 50 mm macro at 1:1, the 100 mm non-IS macro a 73 mm or 75 mm macro or thereabouts (can't remember the exact number for this one).
Kind regards, Wim
Gear: Canon EOS R with 3 primes and 2 zooms, 4 EF-R adapters, Canon EOS 5 (analog), 9 Canon EF primes, a lone Canon EF zoom, 2 extenders, 2 converters, tubes; Olympus OM-D 1 Mk II & Pen F with 12 primes, 6 zooms, and 3 Metabones EF-MFT adapters ....