How Much Do Window Screens Impede Ventilation and Sunshine?

I have an 18' by 18' bedroom with only 3 small vertical windows on one wall. Not much in the way of natural light or ventilation. The windows have no glass, but rather double screens (one attached outside, the other attached inside). Well, I removed the screens to paint the metal window frames because they were getting rusty. I immediately noticed a stronger rush of air into the room and it seems a little brighter in there too.

I am now debating on whether or not to replace the screens as they were, or leave 'em off after I paint the window frame/security bars.

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