"axolotl" wrote in message
...

I presently use an old Edroy that works well but has too short a working
distance.
Are there any grades between the $35 B&L and the $350 Zeiss?

Kevin Gallimore

For longer working distances with adequate magnification you really need
ones with two lenses like what dentists use. They have a positive lens in
the front and a negative lens in the back to make a small Galilean
telescope. To be compact and have a good field of view, the lenses have to
be steeply curved. If each were only a simple lens the image would have lots
of spherical and chromatic aberration. A high quality magnifier will have a
cemented doublet in the front and perhaps 3 lenses in the back which is why
they are so expensive. Even so, the field of view is limited.

I have seen things that look like this on ebay for $50 or less. Obviously
these are not great quality but can you even be sure they contain more than
one lens? Otherwise the cheapest I have seen from reputable dealers is $189.
I am an optical engineer, and I do not understand why someone could not make
something like this with plastic lenses for even less than $50. The field
of view might only be, say, 30 mm or so, but I think there might be an
application for that for machinists.