IR light transmission.....Lenses

[aim54x]

I was hoping that someone here can shed some light on this....

I have just had a D80 converted to be a dedicated 720nm IR camera, so I will be full of silly questions about IR photography for a little while whilst I get up to speed. Todays question revolves around lenses. I am aware that some lenses are better suited for IR photography than others due to hot spots and sharpness, but has anyone ever heard of lenses having differing levels of IR light transmission?

I suspect my Tamron SP 17-50mm f/2.8 does not transmit as much IR light as my other lenses, and my Tokina 10-17mm Fisheye transmits a lot more IR light (even after I correct for its visible light spectrum overexposure tendency ~1ev).

[surenj]

I suspect my Tamron SP 17-50mm f/2.8 does not transmit as much IR light as my other lenses

How has this translated into any issues that you may have?

[aim54x]

I suspect my Tamron SP 17-50mm f/2.8 does not transmit as much IR light as my other lenses

How has this translated into any issues that you may have?

It makes metering even more troublesome!