Ya know, there is nothing wrong with the use of optics, but I prefer to think that 99% of those Old Bastards could probably draw and paint all of us under the table.
The classical apprentice spent 4-5 years of very intense work sculpting, drawing in charcoal, painting in monochrome, and finally in color. Along the way they learned how to grind paint, make mediums, make charcoal, prepare surfaces, and probably swept, dusted and cleaned and cooked a lot!
The standard of the day was the live model, or drawing from your imagination. Some may have used optics, but I believe that is not because they actually needed them - it was a concession to time, or a new fangled thing that they wanted to experiment with. Vermeer may be the only exception to that, although it is still controversal as to whether he used optics as well.
No, I prefer to think that they were simply as good at making art as we credit them with. That means that if humans in antiquity made art that incredible - then there is hope for us too.
