"Les" wrote : Is there any rule of thumb on how close I can be and still
safely watch (not a casual glance) arc welding without any eye protection?
(clip)
^^^^^^^^^^^^^^^^
The eye is just like a camera--the farther away the smaller the image, but
the brightness stays the same. By standing farther away, you are damaging a
smaller area on the retina. How large an image are you willing to damage?