For those who do not know, plein air is the technical term for open air painting.  This is directly opposite to studio painting.  Flexibility is key in plein air painting.  The artist is exposed to all the negative elements of sun, rain, wind and bugs.  On the opposite side the paintings can be brighter as the sun illuminates the landscape.  I am new to Plein Air painting but find that the first impressions give me a new level to my painting.