About the lens...
As it goes, I had to see which lens design and configuration would result in least chromatic aberrations and improved edge sharpness while still being as compact and robust (dust and waterproof*) as possible.
Here “what do I have?” becomes the technical birthplace for the Ocular Perceptual (OP7) close-up lens:
I have shelves of optical prototypes, mechanical experiments, and ideas that never became products. Some solved the wrong problem. Others arrived too early. A few simply waited for the right context.
Among them are optical designs originally developed for the LCDVF and LCDVFe optical electronic viewfinders. Those projects explored image magnification, eye relief, distortion control, and contrast—problems that, at first glance, seem unrelated to close-up photography.
But what if the problem is viewed from the opposite direction? Instead of designing optics for the eye to comfortably observe and follow a scene, could the same principles be inverted to help observe subjects at close range?
For close-looking with a camera, the magnification can’t be too high nor be too mild as cameras like Fujifilm X100VI and Ricoh GR IIIx already focus quite close.
But not that close.
Plus, many camera lens are not that sharp at minimum focusing distance.
So, this close-focus working distance opens up new qualities too - the whole focus range of taking lens gets “remapped” so infinity focus will be at one’s fingertips literally.
Based on my observations +7 diopters (or focal length of 143mm) was fit for medium-wide** lens use.
**Which roughly translates towards: “Can be comfortably held with 35mm to 50mm FL lens in full frame (135) format.”
After some outings it was also evident that the Canon 250D type close up lens (+4 diopters) provides no benefit here as it is intended for portrait and telephoto lenses. +10 diopters is too aggressive as might be +8 diopter close-up lens from NiSi (49mm thread) albeit that is the closest one which also delivers natively on Fujifilm X100VI (despite the mild pincushion distortion).
Don't manufacture capability.
Remove the burden that prevents existing capability from participating.
Disclaimer on header Seiko image: Canon R10, RF 50mm f1.8 STM @ f8 + OP7 prototype lens.
Out-of-camera DepthComposite (in-camera automatic stacking) jpg output.
Seems that Canon stacking algorithm likes some field curvatures better than others.