amfoto1 Loc: San Jose, Calif. USA

The Toki 11-16mm is known to be quite prone to flare... more than many other lenses. There's not very much you can do about it other than experiment with different apertures to see if it's reduced at some and try changing your position slightly to see if that helps. I know folks who bought one but couldn't keep using it because of the flare.

The Toki 12-24/4 is much less prone to flare issues, though if you try hard enough you can cause it or most any other lens to flare at times too. Ultrawides are the most "at risk" for flare, simply because their extreme angle of view makes it more likely that some bright light source will be within the image area. Zooms, with a lot more internal elements, are more prone to flare, too.

But, if you just gotta have f2.8 in an ultrawide, it's been the only game in town for some years. And other than the flare issues (and a rather narrow range of focal lengths), it's sharp with very well controlled distortion and quite well made.

I haven't had opportunity to try the new Tokina 11-20/2.8 that's superseded the 11-16mm. Maybe that handles flare better.

camerapapi Loc: Miami, Fl.

Although flare is not a rare event when using a lens against the light source if I were you I would send to Tokina those images with Exif information for their consideration and advise.
Modern lens coating have reduced the flare but as you saw it is still present.
Notice, I am sure you did, the strong keystone effect caused by a wide angle lens when the camera is not level.
This could be corrected with software but be ready for a significant cropping of the image.

forjava Loc: Half Moon Bay, CA

Green flaring is a common problem with uncoated glass.

I suppose there could be some coatings that do not do well with green flare, possibly on your lens.

The X4 polarizer coating is double-sided and explicitly addresses green flare. Maybe they make a CPL filter that would fit your lens.

That said, adequate answers are likely in the discussion already.

Jim Bob

No and no. You're shooting directly into a light source, my friend. Expect flare. Tokina has not mastered this issue on their multi-coated lenses but you simply need to remember that when composing your shots just as I remember that many Nikon cameras notoriously over expose. I adjust exposure compensation to correct it. You have an exceptional lens. Use it.

kymarto Loc: Portland OR and Milan Italy

The Tokina 11-16 is known to have terrible lens flare. That's the main reason I got rid of mine. My Signa 8-16 is much better.