I was asked this question the other day. That was the question when I mentioned I paint outside. If you know me, you know I do not like to call attention to myself. I grew up in NYC and learned that calling attention to yourself is never a good idea. You become a target. So, no I don't like all those people looking. But, the alternative is worse.
To clear things up, the person asking this question was referring to people making judgements of my art. She was not concerned about safety issues. Regardless, if you are a plein air painter, you know you had to overcome at least three obstacles.
The first obstacle is let go of responsibilities and make time for yourself. This may mean you have family to take care of, school work to do, or any other obligations. For these responsibilities you may need someone to take over or schedule another time to take care of it.
The second obstacle is getting to the location. This may sound simple, but it is not. You have to figure out what is enough to carry and how much weight you can handle. Do you need that plein air umbrella so you can paint in the shade. The shade is not only for comfort on a hot day, but also to make sure your values on your painting is correct. Okay, add 2 pounds to gear. Should you bring only the essential paints or have a limited palette to mix the right color. Remember that you only have three hours. Light changes constantly and by noon the shadows will be flat. Okay, add another 2 pounds. What about parking? Or should you take public transportation?
The third obstacle is the weather. Try to find a day when the weather is not too cold or too hot. Good luck with that in Chicago. When there is no rain and the plein air umbrella won't get blown away from the wind. Try to find this ideal weather after all your other obligations is done and perhaps it is a Saturday or Sunday.
If you make it through these three obstacles, you made it so far. People making judgmental comments about your art doesn't matter. You know that painting from life is better than looking at a photograph. A photograph cannot capture more idiosyncrasies than your human eye. Knowing the difference makes you a better artist.
What is the alternative? Paint from a photograph. Paint from still life set up. There is a time for this. You should still do this. Do not refrain from painting outside because of other people that cast judgements. They will still find you in your studio or when you exhibit your work. There is no escaping criticism unless you do not show your work at all.