I have never seen a total eclipse of the sun, but I have seen a number of partial ones, sometimes with up to half the sun covered. I don't know exactly how much that reduces ambient light, because light from the sky is added in there, but the day is certainly dimmer.

It is amazing how unnoticable it is to the casual eye that half of the solar disk has been covered. If I didn't know there was an eclipse, and wasn't deliberately looking for the slight dimming of the surroundings, I would never have noticed it. The sky was slightly darker, but not anything that would attract the attention of someone preoccupied with daily activities.

I would bet someone on Mars would still perceive a noontime landscape as "brightly lit."