hey,

thought i provide 2 images that clarify the prob. this is not my actual object, this is just for clarification. the first is how i want it, but then with a whiter plane. the second is a picture of the problem. one can see the point of the plane in the lower right corner. it's black there, because the image plane is not positioned that low. the left top corner of the image plane is refracted BLACK in the sphere. it should just be refracted white. this way the shadow is not visible. it seems as if in refraction the use background shader does not see image planes... therefore it uses the default background color (black). if i change the background color of the environment to white (and delete the image plane), nothing changes, and the plane is refracted black as well. by the way, if i turn reflections on, the white background will turn the whole scene into whiteness, so it's not an option either way. help.