Art Renewal' attacks on David Hockney

David Hockney states, in his 2001 book: "Secret Knowledge" that the old masters of painting used projection methods, like the "Camera Obscura" and "Camera Lucida", to improve on their drawing.

Brian Yoder van Art Renewal writes:
Giacomo di Lindini writes:

Hockney claims that the Old Masters couldn't really draw and paint realistic images and that the improvements in image quality over time (particularly in the Renaissance and the 19th century) are attributable to the use of successively improved optical devices such as the "camera obscura" and "camera lucida".
Hockney does not claim that the old masters could not draw, he merely states that they used projection techniques as an aid.

(...) these aids rely on the substrate on which images are projected being white. Once a layer of darker paint is applied, it becomes difficult to see the image. This would have been particularly difficult in eras with less than perfect optics and glass, and before the availability of bright artificial light sources. Worse yet, it becomes very difficult to see colors and their relationships when the projection is done on a multi-colored screen (as any half-painted paper or canvas would be). If the original sketch were made and then covered by a layer of paint, the artist would have to constantly be re-projecting the image back onto the partially painted canvas in order to get the next level of detail incorporated into the painting. That would't have worked very well, especially for dark-colored paintings and for subjects illuminated by dim light sources. (...)
This is true, however, when the projection techniques are only used als a drawing aid, setting the outlines of the model or the portrait, and calquing them, like carbon paper, on the canvas, then the projection method would be possible, That is exactly what Hockney says.

The writing by Brian Yoder is filled with fallacies and personal attacks on Hockney himself, exaggerations of his writings and negative comments on his works. I believe that Hockney's thoughts might be true, because there is evidence in favour of his theories. But far more important than painting techniques to me is, that Brian Yoder of Art Renewal defends the arts against attacks on its impeccable technique. By doing that, he shows belief in that the quality of art has something to do with the technique used. If a painting is 'eyeballed' it has a certain quality, but if the same painting is 'projected' its quality diminishes? The same painting?

I do not and will never support the thought that the quality of a painting lies in the knowledgi I have of how it was made. That is a naive definition of the quality of art.