[Bug]: Imagen3 Capability leans towards generating white or light product background image too often

### File Name

imagen3_image_generation.ipynb

### What happened?

Hi there, we have been using Imagen2 to create product background images with some great results. We are interested in improving these by using Imagen3 Capability, but when testing it out we have observed it's preference to generate white or extremely washed out product backgrounds, which is not what we are looking for.

Could you adview how perhaps the base prompt is different with Capability vs. Imagen2 product background image mode, and if there is a way to get the results we are looking for? Would be very happy to share examples or discuss in more detail with one of the product team.

### Relevant log output

```shell

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### Code of Conduct

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