Until ~two-thirds of the sun is blocked out, it's not as noticeable while you're viewing the progression... but yes, there is a dimming (think about it... there has to be since the sun's disk is partially covered). Once you get within a few minutes of totality, then the darkening gets quite pronounced. For sure: you wouldn't want to be playing baseball without the stadium lights on... which would mess with the experience for the fans.
“During the partial eclipse, the Sun is as bright as usual.”
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Clarification - the uneclipsed part of the sun is as bright as usual, no brighter, no darker.
Overall, the Sun output reaching us is obviously getting smaller, as the uneclipsed disk itself is getting smaller, so the earth is getting darker even during the partial eclipse.
However, the Sun disk is about million times brighter than the corona, so even just a little bit of disk will outshine the corona.
So only during totality, we can actually observe the solar CORONA, which is why the totality is soo special!!!
Please, do not settle for partiality, you must see the totality! It is unbelievable!
You will never forget it and ask for more.
That why there are those eclipse chasers, who do not spare any expense or safety, just to go to all kind of places for couple of minutes look at the corona.