Ben, probably 99% of anything I shoot in Australia with a wide angle like these, I use a tripod and always shield the lens from light, usually better than any lens hood, especially an extra wide lens hood.
With the Tamron 17mm it had problems when faced into the light, more so if I was exposing for something that was with the light behind the subject. The flare was nearly always problematic if I had more than one colour temperature of light. Some really bad ones were when I did a series of shots inside a shearing shed with warm sunlight coming in at a low angle and with some holes in the roof cold blue light coming in from the top.
Under these conditions the Tamron was certainly not the best lens if using colour film, with B&W it was not an issue. The time I visited the same shearing shed with the Sigma 18mm I did an almost exact replica shot using colour film and although the same colour temperature differences were almost identical, they were, compared to the Tamron, greatly reduced.
The second time I was there, with the Sigma, I was alongside a mate with his F3 and his Nikkor 15mm rectilinear. There was really no comparison between the two. One was a moderately priced lens for what I am, a happy go lucky shooter, the other was intended for the professional market and at the highest end. The Nikkor 15mm also had the same colour flare, but one really had to look to see it. Although to be fair, the 15mm lens made the colour flare bits that much smaller in the frame.
I don't remember if I had the lens hood for the Tamron 17mm, to be honest.
Mick.
From my QWERTY tap tap laptop