Observing the red circle with normal ring illumination makes the difference between halation and shadow large and very difficult to observe.

Halation can be suppressed by using quadrant LED ring lighting and lighting only in the longitudinal direction.

if the light intensity is increased, Observation of R part becomes possible.	If you increase the magnification as it is, It makes observation of R part easier
Using a diaphragm lens further increases the depth of focus and makes observation easier.
＜Open the aperture＞	＜Close the aperture＞

 

However, if you use a diaphragm, it will become darker and the resolution will be slightly lower. So, our lens will be in the practical range up to about 120 times.