Hello all, I too have used an Optivisor for years. I started out with
a #3, but quickly switched to a #4. I liked the focal distance of
the 4 much better.
As others have stated, you really need to balance your need of
magnification with the distance in which you are able to perform
that task.Over the years, I have experimented with many different
strength plates, and have come up with a solution to the problem I’d
had in being too close for one task, too far, or without enough
magnification for another. I added a second lens plate to my
Optivisor, by way of a small, modified hinge.I currently have a #5
as the main lens, and have an additional flip-up/down lens I can use
for setting or engraving etc. I can switch (the power of) the lens
plates by way of the plastic rivets. They will allow the lenses to
just pop right on & off. If these rivets are too loose, I just
spread them open a bit with my bench knife.
This system also works well as a flip-up/down system for platinum
welding, using a glass welding shield instead of the 2nd magnifying
plate. Ping me off line if you’d like me to make one for you. it
works well for me.