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Haven't sprung for this lens yet (hoping to hear from people who have!) but I decided to do some research into focal breathing since it's a hot topic with 70-200 lenses lately.
Using the minimum focus distance and the max magnification provided by B&H on their spec sheets, I was able to calculate the focal length at minimum focusing distance. Now, the max magnifications and the minimum focusing distances provided are likely estimates, not the precise values that you might see in a patent application, so assume some margin of error with all the following, maybe +/- 15mm.
Tamron 70-200 G2: 156mm
Tamron 70-200 VC: 163mm
Nikon 70-200 VR II: 168mm
Sigma 70-200 OS: 175mm
Nikon 70-200 FL E: 231mm
Canon 70-200 IS II: 240mm
Canon 70-200 IS I: 250mm
EDIT: If you account for the length of the lens, you get different values as follow:
EDIT 2: Now also adjusting for flange distance in parantheses:
Tamron 70-200 G2: 124mm (117mm)
Tamron 70-200 VC: 139mm (133mm)
Nikon 70-200 VR II: 143mm (138mm)
Sigma 70-200 OS: 150mm (144mm)
Nikon 70-200 FL E: 188mm (179mm)
Canon 70-200 IS II: 200mm (192mm)
Canon 70-200 IS I: 218mm (211mm)
If the above values are correct, the following conclusion is not.
So interestingly, of these popular 70-200 lenses, none of them are 200mm at minimum focusing distance (nor even all that close, even if you factor in the imprecision). The lenses lauded for being true 200mm lenses are really well above 200mm, and the lenses that some people have said are really 135mm or 115mm lenses are actually closer to 200mm than we think.
But what about 200mm primes? We consider 200mm primes to be 200mm at all focal lengths, but as it turns out this might not be so true. Based on the specs of the latest 200mm f2 lenses, the Canon comes in at 238mm and the Nikon comes in at 250mm. (EDIT: 211mm (206mm) and 225mm (219mm) respectively, when considering lens length.)
Again, these focal lengths are not 100% accurate since there's so much rounding in the specs. But it's pretty clear that there are major differences in focal length at minimum focusing distance, and that if you compare one of the Tamrons, the Sigma, or the Nikon VR II against a prime, Canon 70-200, or Nikon 70-200 FL E, you'll think that the Tamron/Sigma/Nikon VR II is a lot shorter than it actually is.
Edited on Mar 06, 2017 at 10:10 AM · View previous versions
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