To quote the small relevant section:
A T-stop (for Transmission-stops) is an f-number adjusted to account for light transmission efficiency (transmittance). A lens with a T-stop of N projects an image of the same brightness as an ideal lens with 100% transmittance and an f-number of N. For example, an f/2.0 lens with transmittance of 75% has a T-stop of 2.3. Since real lenses have transmittances of less than 100%, a lens's T-stop is always greater than its f-number.[6]
Lens transmittances of 60%–90% are typical,[7] so T-stops are sometimes used instead of f-numbers to more accurately determine exposure, particularly when using external light meters.[8] T-stops are often used in cinematography, where many images are seen in rapid succession and even small changes in exposure will be noticeable. Cinema camera lenses are typically calibrated in T-stops instead of F-numbers. In still photography, without the need for rigorous consistency of all lenses and cameras used, slight differences in exposure are less important.
The reason why "T-stop" is missing in general from "still photography" discussions is that it really doesn't tend to be a "major factor" to take into consideration, from what I've seen...
One area where one might be aware of is when you are shooting with some lenses (for instance, my 100mm macro), the transmission is actually cut down as you move toward your minimum focus distance, I believe by about a stop. This is, I believe, by design, not a "flaw". At any rate, if you are doing Manual Exposure with a lens like that, keep an eye on things, you may (or may not) want to compensate for that, or at least be prepared for a stop of "under-exposure"!
As to the question/issue of the OP, well, no matter what lens the OP is using, if the shots are under-exposed and require "boosting" in PP, well of course there will be more noise! If the lens being used tends to get a lower exposure than other lenses (the "T-stop factor") then I'd simply ask about that rather than just throwing out a term that is virtually unknown in the still photography world!
