Tamron 45 mm 1.8 VCD underexposing on D850
Tamron 45 mm 1.8 VCD with D850 always underexposes (with iso 64 and Flash in TTL mode) .. to overcome this I dial in 0.3 to 0.7 exposure compensation. Nikon lenses 35 mm 1.8G and %0 mm 1.8 G doesn't have this issue.
Any idea why this is happening? Does Tamron lens transfer lesser light to sensor or is it the issue with communication protocol that Tamron has reverse engineered?
I am expecting TTL Flash to compensate for the lack of light as I am using manual exposure mode.
Same combination is working fine with Nikon primes of similar focal lengths.
I compared Nikon and Tamron lenses with same exposure settings in same area and lighting.