Type camera matching into Google and look at the videos that explain how to match the angles. (there are a lot of them.) Any of them can be applied to Poser, doesn't matter what they were created in. All of them are going to explain how to figure it out with a primitive or low res model.

The main shadow lighting can be figured out at the same time, just remember to use an infinite light or a spot light that is as far away from the center of the scene as possible.

Fill lighting can be created with just about any HDR image with similar colors as the background you are trying to match. You can also do some of the light matching in a paint program on both layers. The background, and the render you are pasteing over it.

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