So I wanted to know if there's a way to calculate true focal values for the lens (for portraits) keeping in mind the focus breathing this lens is prone to (as well as many other 70-200's for other systems).
Reason is - trying to figure out if it's worth getting a faster prime to play with (something like SY 135 f2, 85 1.4 or Mitakon 85 1.2), or just stick with the 70-200 and avoid spending (boring I know).
the tamron lens is sharpest at 135mm focal length, but is it a true 135mm, or it's in fact shorter, closer to say a 100mm? If it is shorter, then I guess Samyang 135mm would give me more background blur even at 2.8, and especially at f2?
Mainly talking about portrait distance, maybe waist up format, head and shoulders etc. I believe focus breathing is much less prominent at longer distance, so I guess environmental portraits aren't as affected by it.
Basically, doing some theory crafting and researching while I'm waiting for my camera to come back from repairs lol, and maybe start an interesting discussion?
Also would be interested to know if there's a way to calculate dof with different focal lengths while keeping the subject the same size. Not sure if I'm phrasing it correctly, it's just dof calculators only work with distance from lens to the subject, and not subject's actual size. 135mm f2 seems to give shallower dof than 85 1.4 or even 1.2 at 3m distance to the subject (0.054m vs 0.099m), but I'm guessing it might be too close to the subject with the 135mm, so I'll need to go further back.