lets say that i have a box and a sphere, the box have a red color,the sphere have different color,both have a different material. how can i use multipass to have each object its own output in Photoshop ,so i can adjust the color or the material of the box individually without affecting the sphere material .
First you have to give each object a compositing tag. Then, in the tag's Buffer tab, asign each object a unique number. Next, in render settings>multipass, add two buffer passes with the corresponding numbers.
Cinema will then render out an alpha for each object which you can use as a luma matte in AE.