Capturing white can be challenging. Here’s what I’ve learned — set the exposure low. It’s much easier to increase exposure in editing then it is to decrease exposure while maintaining details of the photograph. So err on the underexposure side.
Set the exposure so it under exposes the white thing you want to focus on in the photo. In the first two photos I wanted to focus on the white dress. The second two photos I wanted to focus on the room itself.