Interesting question. I’m nearsighted. Not catastrophically, but
pretty seriously. (20/150 or thereabouts) On the plus side, both
eyes are about equally screwed up.
I’ve found that prior to getting a microscope, I definitely
preferred to engrave with my contacts off. In speaking to my
optometrist, he said my particular error rate was roughly equivalent
to having a 2x loupe built into my face.
As I’ve hit the upper reaches of 30, I’ve noticed that I’m having
more trouble focusing in close, which makes me more dependent on an
optivisor, at least with my contacts in, but with them out, I can
still focus in very, very close. I suspect that a nearsighted
jeweler would have had far fewer problems doing that sort of chip
carving than you’d expect. Having done some silver chip carving once
upon a time, I suspect he may have been feeling some of the finer
details, rather than depending entirely on his eyes.
You have seen the old (15th century) engravers globes with the glass
ball of water and the candles, right? (for focusing light on the
work.) There may well have been something similar in use. Being both
fragile and mostly organic, that sort of thing is unlikely to have
survived. A serious thing to think about is not only how they saw
what they were doing, but how they illuminated the work.
Out of habit, I do delicate work with my contacts off, even using
the microscope these days. I’ve found that while I do get a
magnification boost from going bare-eyed, there doesn’t seem to be a
similar boost when looking through the microscope bare-eyed. Focused
is focused, at whatever mag rate is set.
Hope that helps. N=1