I've heard of such, but sincerely think it's more like an urban legend. I'm not an exception and use lot's of reference photos , and sometimes I paint entirely form the photo.
Let's assume a best case scenario and that you own a good camera . Even though it will give you decent quality photos , it still will never fully transfer the true colores - So here is the little trick without getting deep into Photoshoping
Open your photo in any preview or editing programs and adjust it to make it significantly warmer and lighter..And I mean lighter! Try to print a large photo - you can see all the gorgeous colors in those shadows.
Anyway , here is an example of a plein air studies, with a studio touch ups .
|"The Horsthief Lake" 9x12, oil on linen|
|"River Bank" 9x12 oil on linen|
|"Mount Baker" oil on linen , 8x10|
|'Columbia" oil on linen , 10x10|