01-29-2013, 08:42 PM
Playing with four different formulas that provide four different answers and I'm still not convinced any of them are correct.
Usually when things like this happen, you can feed the possible answers into other formulas and prove known values. I haven't been able to do that so far.
If I were to hazard a guess, I think BC's calculator is probably the most correct. Why? Because, the AoV is correct, the magnification is correct and the value for Xi is the exact same number I calculated for focal length. I never got into the bellows factor.
This guy has a lot of good information but he is getting it by having a lot more data on each lens then we have on the 70-200 f/4. I went looking at Nikon's patent stuff for the lens but couldn't find the detail required.
http://www.pierretoscani.com/echo_focal_length.html
Usually when things like this happen, you can feed the possible answers into other formulas and prove known values. I haven't been able to do that so far.
If I were to hazard a guess, I think BC's calculator is probably the most correct. Why? Because, the AoV is correct, the magnification is correct and the value for Xi is the exact same number I calculated for focal length. I never got into the bellows factor.
This guy has a lot of good information but he is getting it by having a lot more data on each lens then we have on the 70-200 f/4. I went looking at Nikon's patent stuff for the lens but couldn't find the detail required.
http://www.pierretoscani.com/echo_focal_length.html