Do you have a way to determine the position of the light source of a background picture to place correctly the light in a scene ?

Thx

Look at the shadows in the background.  Long shadows mean that the light source is low, short shadows the light source it high.  If shadows are behind objects in the scene then the light source is coming from in front. If there are not shadows then the light is more ambient and can come from any source.

If there are any shiny spots on objects in the photo, you can also use them to judge where the light is coming from - basically, if there is a shiny reflection to the left of the camera viewpoint, the light is coming from behind and to the left of the camera.  If there's a reflection in the upper right, then the light is behind, above, and to the right of the camera.  Etc.

can't these be looked up in the lighting settings, or am I missing the point? (we are not smart...;)

I believe the issue is with an imported background picture.  As this is simply a graphic file layered behind the active workspace, there would be no reference for lighting settings.  The idea is to identify where the light source(s) are in the 2d graphic layer (ie the direction of the light or lights illuminating the static background scene).

If lights in the workspace do not mimic the lighting of the background, the 3d image will not merge realistically into the background when rendered.

The tips above are the best way to estimate this, IMHO.

Klebnor

Thanks all !