Dxo seems to be the popular reference point for lens T stops, so I thought I’d try testing two lenses that they report has having very different transmission, the Canon EF 35/2, reportedly with a T stop of 2.0, and the Tamron 45/1.8 with a reportedly rather dismal T stop of 2.3. The Tamron has always delighted me with its openness and breio, so I was surprised that it’s actual transmission was not as efficient as the Canon.Just a thought, but given the headline name of a lens is usually a rounding of the actual aperture (T versus f), is the difference between 1.2 and 1.4 potentially even less than it seems?
I shot them for identical exposure in manual and raw, and at different apertures. The exposure appeared to be absolutely identical, which I found strange as according to Dxo the Tamron should have been a third of an EV darker, which would be most certainly noticeable.
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