"Resolution" and "contrast" affect image clarity. Resolution refers to the distance between two points, for example.

The human eye has a resolving power of 200um (=0.2mm) at a near point of 25cm.

What does that mean? It means that when the distance between these two points is less than 200 micrometers, we can no longer see them clearly.

At this point, we need to use a magnifying glass or microscope to enhance resolution.

The good microscope has a resolution of 0.2mm, which is about 1,000 times that of the human eye.

If the magnification of the microscope exceeds 1000x, we must use a special oil immersion lens.

Otherwise, the magnification ratio is invalid, as it begins to blur.