The capabilities of cell phone cameras are amazing, performing better than my classic SLR lenses. Here is how I used a simple analog loupe with my cell phone to do some great macro photography.
Recently I went to change the keyboard of one of my Acer laptops. As I disassembled it, the tiny mainboard connector part came off . It clamps the keyboard ribbon to the laptop’s mainboard.
It just wasn’t going back on. Part of the issue was that I was not sure which way it went back together. This side down, or the other side?
So I got out my photographer’s 35mm loupe to take a look. I could see a lot of very tiny teeth that had to be matched up.
Then I decided to take a few pictures with my Nikon D200 DSLR. I’d done a lot of 35mm photography in the past, and had a number of lenses and ways to do macro photography. The really nice thing about Nikon, is that they never changed the camera lense mounts. So all the prime lenses that I ever bought, can still be used on my DSLR.
One way to do macro, is to use a close up lense. You remove the UV filter from the lense, and replace it with a curved “filter” which then allows you to get a close up of the object.
The other way is to use my Vivitar Macro 2 times converter. This fits between the camera body and the straight lense.
I tried both ways, and looked at the results. But they didn’t look very sharp. Even though I’d used the tripod, and a small f-stop. This bothered me.

Then I tried my cell phone, a Motorola G4 Plus. Using no magnification at all, it was actually possible to get a close enough focus to see the better detail.

Using the digital zoom, the result was actually sharper than my prime lenses and macro converter. Wow!
I’d been looking at the parts through my 35 mm loupe.

Then I had to idea to try using the cell camera with the loupe.

The results were impressive!
Here’s a picture of the mainboard connector using my classic lenses on macro.

And here’s a picture using the cell phone and the loupe.

Using the digital zoom, the cell phone and loupe is actually sharper than the 35mm prime lense and 2x macro convertor. Wow!
As I think about it, there are a few reasons for this.
Close focus: the cell camera has a much closer focus than the classic SLR lenses.
Auto focus of the cell camera vs the manual focus of the classic SLR lenses.
Distortion:
One thing to be aware of, is that the simple loupe that I have actually distorts the image somewhat.
Looking at a drafting triangle
the line of the ruler is not straight

In the end, with the help of the pictures, I was finally able to put the two parts back together.

Useful Links:
After I used my loupe and cell phone, I discovered that I’m not the first to do this.
Pro Watch Photos Shot with an iPhone and a Jeweler’s Loupe
https://petapixel.com/2016/07/28/professional-watch-photos-captured-iphone-jewelers-loupe/
Loupesystem Store
https://www.loupesystem.com/collections/all-items
Loupes at BH Photo Video
https://www.bhphotovideo.com/c/buy/Loupes-Magnifiers/ci/987/N/4077634476
Hope it’s useful.