How do I get a totally consistent white tabletop background?

Question

I'm working on a project that involves filming playing cards, and then cropping/joining different parts of the video. For a seamless result, the background of the video needs to always remain the exact same, so a side by side of different timestamps doesn't look edited. I've found when I film, my iPhone camera is constantly changing the colour/lighting of the backdrop depending on what's in frame. This is not a result of any actual shadows that are created, I can see the table appears the same in real life while I film. I've linked an example video of this happening just by moving my hand in and out of frame.

I've tried several "raw" and "manual" camera apps which lock focus/exposure/white balance, but they all have this issue. Is this something unique to the iPhone? Would I have this problem with another camera? Please advise!

Example: https://i.imgur.com/yGbGIVh.mp4

Answer 1

That's interesting. Just tried it with locked AF/AE in the camera app as you showed, and it definitely is adjusting the white background even though the focus and exposure are supposed to be locked. Same with MAVIS and Filmic Pro too, where you can lock the white balance.

Usually when someone films seamless white, they are shooting upright rather than top down. They light the background so that it exposes at 100% white, then light the foreground so it is correctly exposed. The problem with top down is that you can't separate your foreground from your background as easily, so I'm not sure what the correct setup would be here.

A softbox (or a lightbox) pointing towards the camera, with additional soft lighting for the cards and hand.