Krasnogorsk's Zenit Meteor-5-1 17-69mm f/1.9 in T stops

[Owen A. Davies]

Does anyone know if the T stops were ever measured for the Krasnogorsk's primary lens, the Zenit Meteor 17-69mm. For the sake of metering, I'd love to know how much actual light the lens lets through. I haven't seen any info on this posted anywhere. Thanks. 

[Dom Jaeger]

Most zooms like this lose around a third to half a stop. Damaged coatings or internal fog will add more loss. I'd probably rate that zoom at about T2.2.

As a general rule, primes lose less than a quarter of a stop, modern zooms a sixth to a third, and older zooms between a third and two thirds of a stop. The number of elements play a part, so larger zooms will lose more.