As you have probably found with google there are no accepted standards as to what makes a painting a plein air piece. To keep oneself from becoming a prevaricator it would be wise to work on it at least a portion of the piece on location, outdoors. Beyond that it is up to the artist on how much studio work they want to do on it.

However, when it comes to shows and events, most of them have a set of rules to be followed and some are very strict saying it must be 100% done on location, others less so. The least restrictive I have looked at participating in allows a max of 25% studio work. They don’t specify if that is per square inch or a time related percentage.

I heard a story from several reputable sources about a fairly well known plein air event less than 4 years ago that didn’t have a very strict set of rules and was not monitored. According to those telling the tale, one of the participants who is a relatively famous plein air painter, spent almost the ENTIRE TIME in their motel room. None of the artists there ever saw them leave their room for the week long event, nor were they spotted painting en plein air. Their car sat in the parking lot for most of the time. They won some awards and sold a bunch of paintings.
Nobody chose to rat them out.

This thread of mine on WC was created when I had similar questions to yours but more related to shows and events.

https://www.wetcanvas.com/forums/showthread.php?t=1420321

For plein-air my intent is to do the entire piece outdoors in front of the subject. I feel that if I must I can do this in several sessions and I know of some others who paint for weeks, always with the light just so for an hour.

That said, I will do some rework after the fact if the piece needs and deserves it and sometimes that will be done in the studio, in my car or at another painting site.

…and having said that there are times when I set out to only start a pen & wash piece plein-air with the intention of finishing it at home. This is when I’m far from home and need a number of pieces. By doing this my motel and meal expenses are greatly reduced. I make no claims that this is plein-air work however… and no one has asked.

Yes I know there are those who “cheat” at events and organizers who “wink” wanting only sellable art… but I also know there are buyers who do not know what plein-air means and having been told don’t care.

Dave

Alla prima vs. en plein air.
Unless it’s in a contest rule, who really cares? it’s your painting and it’s your time and method.
But I prefer to do it alla prima – all at once – and since I start mostly plein air, that’s where I finish it. It’s not that I don’t study it to see what I might have done differently. Just a personal preference not to touch up a painting (OK, I’ve done it on rare occasions, but nobody was watching! LOL)

…At this year’s Plein Air Conference and Exo in San Diego, I will ask Eric Rhoads, the organizer, specifically what he considers a Plein Air painting to be.

Please do! I’d love to hear his response.

But of course, unless it is a contest, it doesn’t really matter. After 2 or 3 hours the light has changed enough so that you are just making stuff up anyway after that point.