Is it an AE flare or Knoll or Optical Flare from Videocopilot?
The second and the third type you can link the flare to a Light- parent the Light to the 3d layer that is your photo and position the lightflare to the desired spot and now the flare will move with the photo.
For the first option (native AE flare) - pre-render your animation and then track- it should work just fine.
I use Optical Flares... but there a re still a few minor problems.
I used a pointlight and adjusted the z value just so that it's right "above" the photo which I turned into a 3D layer as you said.
obviously the light now effects how the photo looks. but if I switch it off, the lensflare disappears too.
I had problems in the beginning with understanding what you meant by "link the flare to the light". I guess you mean switching the positioning mode inside the optical flares properties to track lights? once I do that the flare is attached to the light and moves with it. but again... if I turn off the light, the flare is off too.
What am I doing wrong?
It works now!
I must have done something wrong before... just went through the whole procedure again and now I can switch off the light and the flare is still there.