using the exiftool to retrieve the focus distance. The physical target distance (3 meters) was the same for all lenses. I also have 2, 28-105mm D lenses.

Nikon lenses focus distance

35-70mm 2.9 meters
18-200mm 3.0
28-105mm #1 2.7
28-105mm #2 5.8


Tamron

17-50mm 12.0
90mm macro 2.8 50.1

Obviously the 2 Tamrons overexposed when using the built in D80 flash in BL mode using matrix metering. It's interesting that the #2, 28-105 Nikon lens reported the focusing distance at 2X the actual and some overexposure is evident.

I really don't have an overexposure problem with the Tamrons as I normally shoot flash with a SB600 and spot focusing which goes into TTL mode automatically. I would like to see the results using a D100 or some other older Nikon body to see if there if there is just some poor electronic data handshaking with newer Nikon bodies. It's had to believe that Tamron would release these lenses knowing that they would overexpose. Also there is the possibility that any Nikon camera body firmware upgrades my have affected the distance reading capabilities after Tamron designed the lens cpu chip.

I also have Nikon, 18-70mm, 55-200mm, 50mm F1.8, and 28-85mm lenses that I will need to test also.