La Vie,
Those links were to really crummy, easily refuted poor arguments.
I quote from the first link, hoodwinked by Hockeny:
"For example, Sweet does not point out that murals, ceilings, self-portraits and moving objects all elude Hockney's mirror-projection method"
Apparantly he's never heard of a cartoon. A cartoon is what you create before you paint a big mural or ceiling. It's paper.
To use hockney's method, you'd trace a reflected camera obscura image onto paper. Then, using an image enlarger, you'd make various enlarged panels of parts of the art on seperate sheets of paper. The image enlarger would be made of wood with a set of levers, you trace an image on the small side, and it gets enlarged by the end of the levers with the crayon.
Once you have your individual pages from the grid of your image, you take a little spiked wheel and perforate the paper along the lines of your drawing. You affix your pages properly aligned to the grid on the wall or ceiling you're painting. You can do this with wax or gum, or tape!
You then take a porous bag of charcoal, and pound it on the paper. The places where you perforated holes will let the charcoal through. This is called a "cartoon" of your image. You then paint, knowing that you have accurately reflected the perspective of your original. AND you did it with tools that were all used during Leonardo's time!
The secondlink is merely a set of Ad Hom's against Hockney, so I am unable to substantively address them. They merely state that Hockney failed to prove his assertion, and then start flinging attacks like :
"...we can see why [Hockney's] reputation has been in freefall in recent years
...
"Hockney's own painting would be laughable were it not taken seriously by the art establishment."
His own attempts at drawing and painting are so incredibly inept, lame - talent less and skill-less - that the root cause of his theory must be a seething jealousy for those who can do, with the naked eye, what he can't do even with his optical aids.
"
The third also seems to refute the general impression one gets to Hockney, but not the specifics of Hockney's arguments. In his book, Hockney is not merely saying the masters "cheated" by tracing things. He is making a more subtle point, that use of these technologies INFLUENCED the style of painting that was popular at the time. A camera obscura INFLUENCED art, because once an artist saw it, it could not be unseen. The reality made available by optics for the first time, and forever afterword, FOCUSED the point of view of all art in the eye of the observer. Previously in art, perspective bounced all around. But single-point perspective was the defining change in art at that time, and it can undoubtably be traced to the new science of optics.
