Numerical Aperture - N.A.

In microscopy Numerical Aperture measures the ability of an objective to gather light. The higher the numerical aperture (NA), the more light can be collected by the lens in the microscope objective. This results in a better resolution and a higher intensity image. A high numerical aperture also allows for greater field of depth and a better overall image.

Numerical Aperture in a high quality 100x Oil Objective is typicaly 1.25.


In Fluorite's that number rises to 1.30.


In Apochromat Objectives the numberical aperture is 1.40

However, don't be fooled. Just because the numerical aperture of a given microscope objective is 1.40, that does not mean it is the same quality as a high quality objective like Nikon or Olympus.

Nikon objectives are some of the highest quality objectives that you will find in the world. Their CFI60 objectives use a 200mm tube length and a wider body (25mm thread pattern) to achieve high numerical apertures and longer working distances. (*The working distance is the distance between the tip of the objective and the specimen.)