Greetings all, if you haven't heard enough from me already; I've been collecting various loupe arrangements and thought I'd share my conclusions. First, I have enough astigmatism that working uncorrected for long periods makes it uncomfortable, but not enough to require glasses to drive. I much prefer binocular vision as well; it just makes everything easier. My first exposure to binocular vision was a Bausch and Lomb stereo microscope when I was winding tape head cores back in the '70s at a college job. They are tiny little things about the size of a pallet fork and a challenge, even with a machine specifically designed for the job. Very similar to watchmaking in regards to dexterity and visual acuity.
I have gathered several basic tools/methods; a Bergeon 2611-TN Jewelers Eye Loupe at 4x/2.5" along with a loupe wire, a pair of CraftOptics prescription eyeglasses with 2x Galilean telescopes, three sets of Donegal Optics Optivisers in 4, 5 and 10 diopter ratings, and a Nikon SMX stereo microscope from 8-40x. I also tried a non-prescription 3.5x Galilean telescope set from Esslinger, but found the alignments weren't adequate (you had to twist the glasses to bring the images together). Here are my conclusions:
The Bergeon loupe is the go-to standard for watchmaking, at least the configuration and power. I like the fact that there's a large opening that you place on the bottom, it relieves moisture and allows you to look through it when needing normal vision; you just lower your view and can look with both eyes to find the screwdriver on the bench. Since you are looking with only one eye, there's no concern with alignment. It does not allow for correction but in my case, the right eye doesn't need too much. I can use it for hours with no strain.
I bought the CraftOptics set after seeing them at the Tucson Gem & Jewelry show for several years, thinking they would be great for multi-use but probably not strong enough for watchmaking. They are made to order for your prescription and are available in three ranges of working depth, the shortest being 12 inches. The glasses are bifocal and the working distance is controlled by how much they tweak the bifocal add. The main part of the glasses are corrected for infinity and allow you to look up to see clock or the cat on the windowsill. The telescopes swing up out of the way and with the telescopes up, the bifocal portion focuses at the working depth specified; when you swing the telescopes down, it maintains the same working depth but at twice the magnification. Very convenient for switching back and forth from zoom to wide angle. They come with an optional LED light attached to the bridge for excellent illumination, but perhaps too bright, even at the lowest setting. The setup as I ordered it was about $750.
As noted above, they aren't strong enough for movement work but are great for band/case work. I have a pair of flexible plastic lenses that were bought to make a cheap bifocal setup in a dive mask at 2 diopters. I was able to put them on the inside of the prescription lenses over the bifocal zone to raise the power. The setup works but you give up the advantage of an all-glass optical path and they mess with the alignment of the telescopes as they were aligned to focus at 12 inches, not the closer working distance of about 4-5 inches. I have used them in this configuration to disassemble movements but the finer needs of aligning a pallet fork/bridge or placing a balance wheel assy are just too much to ask for.
The Optivisors are the go-to solution for many industries from machining to electronics to instrumentation. They have a single glass lens plate that comes pre-aligned and corrected for the working distance (the lenses are tilted inward appropriately). They have a hood to block out overhead light that would reflect off the back and have enough room for corrective eyewear between your eye and the plate so you have corrective optics. They come in a range of magnifications up to 3.5x magnification (10 plate). The headband is infinitely adjustable and comfortable; the visor swings up out of the way for wide angle, or you can just look down below the plate to find the screwdriver.
Optically, they work well although 3.5x is on the low end for movement work. I made up for this with a pair of corrective lenses for computer work with a 1.5 diopter correction across the lens. This shortens the working distance to about the same as the Bergeon loupe noted above and the magnifications are similar. It doesn't cause enough misalignment to be a pain, at least for the 30 or 40 minutes I've tried it. The work must be centered well between the lenses; if moved too far to the right or left, the alignment suffers. If there is a downside to this setup, this is it.
I also bought a set of battery powered LED lights that attach to the lens plate; a row of three above and another below the lenses. The light only has one brightness but isn't too bright to be a nuisance. The only fault that you can just see the lights at the edge of your field of view and that can be a bother. I think a little black paint might help.
The regular OptiVISOR costs around $40-45 depending on plate. The OptiVISOR LX is the cheaper version with a plastic plate. I don't recommend them as the plastic scratches with cleaned, if you are not careful. I don't recommend anything that's not all glass in the optical path. The illuminator was about another $30.
The Nikon SMX is the perfect solution for fine work, examining hairsprings or pivots, any mechanical damage on plates, etc. I added a 40 LED ring illuminator that solved the main problem I had in the past; getting enough light on the subject. The only downside is that it sits on a stand and you have to look down through it so it sits on the side and I bring the work to it. The maximum field of view is about the size of your thumbnail; the minimum is a little bigger than a balance wheel pivot. Obviously, the depth of field is very fine so it helps to mount the work and bring it into focus with the focus rack.
The only improvements I could add are to clean the optics and find a way to mount it so I could bring it into the workspace when needed. It was made in the '60s and has had a hard life so it's pretty dirty on the optics surfaces. I picked it up maybe 15 years ago in a junkyard auction for $30, if you can believe that. I just found the service manual for the SMX-10 (additional camera port and later model) so I may take a crack at disassembling it enough to get at the dirty optics. I also have a computer screen mount that is pretty rigid and swings around like a Luxo lamp (think Pixar intro); perhaps I can rig it up to hold the head.
So my recommendations are the Bergeon loupe and the Optivisor with a 10 plate and readers around 1.5 diopters (that's the number they put on the readers).
I hope this has been informative.
Edit: Discovered the Nikon is an SMX model, not an SM-5 which doesn’t zoom.