What you’re referring to isn’t likely the problematic blooming. The problematic blooming is caused by the physical LED’s being larger than the pixels that contain the content you’re displaying. As this is a physical effect of the interaction between the panel and the backing LED’s, it’s not something you can take a screen shot of. (This is why you see examples where folks are taking pictures of their screens). Because of how your eyes work, the brighter the screen, the less likely it is that you’ll see this effect (it’s like trying to see faint stars in the sky during a full moon).
What you’re experiencing is the normal optical glow your eyes perceive when looking at any bright object with a black background around it (again, like trying to see faint stars on a moonlit night). If you have an iPhone, turn it to maximum brightness, then restart it, you’ll see the same happen around the Apple logo on that perfectly black background, too. When you consider that the iPad’s screen is capable of getting even BRIGHTER than the OLED screen on the iPhone, then the effect will appear more pronounced.