I was very interested in this portrait zoom lens. I spoke to a Tamron representative as I couldn't find detailed specs anywhere on the internet. Speaking to a Tamron rep, she mounted a 35-150mm lens on a Canon 5Div body and checked focal lengths in Aperture Priority AV to find the widest aperture at each focal length. Here's what we found: 35-49mm f2.850-84mm f3.285-104mm f3.5105-150mm f4
Nikon 35mm f/1.8G Auto Focus Lens for Nikon DSLR Cameras - Black (Model 2183)
125 Review
Canon EOS SLR Camera Lens EF 24-105mm f/4 L IS USM
124 Review
Black Canon EF 24-105mm f/4L IS II USM Lens - Model 1380C002
78 Review
New Nikon 18-105mm Vibration Reduction π· Zoom Lens with Auto Focus for Nikon DSLRs
104 Review