It doesn't happen on clear days because there are no clouds to obstruct the sun and cast shadows.
Quit worrying about the clouds that are lit up in the OF. They are brighter because of 2 things:
One, the cloud that is right in front of the sun (remember the crappy diagram) is not covering the sun up enough to cast shadows beyond the outfield of the stadium, where the other clouds are. So they are being hit with direct sunlight, while where the camera is located (near home plate) is in a shadow from the cloud that is behind that point of view.
And two, from that vantage point the camera is in that aforementioned shadow of the cloud obstructing the sun that is positioned behind home plate/3rd base and therefor it needs to adjust the aperture of the camera, which opens up the lens more to allow more light in so that other objects in the shadows don't appear too dark. Thus overexposing the distant clouds in the outfield and past the stadium and downtown areas. Those clouds appear extra lit up as a result of these two factors.
Just know that everything is working as it should be. And honestly, with the upgraded colors this year, the game looks better than ever. The sun is where you think it is during your games at Fenway and the differences you are seeing is a result of real time animated clouds passing in front of it and casting shadows on certain parts of the field and areas around it. Just remember, not every part of what you are seeing is in a shadow at the same time, you can see where is still brighter and lit up when it shades like that. And look for those light pole shadows and players shadows that are stretched out towards the outfield, they are indicators of when the sun is out and where it is positioned. When they start to disappear the light from the sun is lessened because of clouds, or the sun dropping behind the horizon of the stadium.
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