I have never said nor implied this: "... T-stops going up in proportion to the magnification ..."
A zoom with a constant f-stop number: What does that mean for the aperture diameter? (example of 70-200 f/2.8)
- @ 200mm --> aperture diameter of 71mm
- @ 70mm --> aperture diameter of 25mm
So, while the front lens element is always >= aperture diameter, there is no decrease of t-stop value to expect!
Your graph proofs what I was stating.
"However, if you do magnify in front of the aperture then the t-stop is quite different from the f-stop value. While that can be the case for a zoom at some focal length, it makes no sense for a prime."
These three popular primes aren't any different than the zooms cited earlier. They're all about 1/3 to 1/2 stop slower T-stop than f-number.
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