Microscope Magnification versus Resolution

In microscopy there are two concepts that many people often think of as one concept, but they are in fact very different. These two concepts are microscope resolution and microscope magnification. From a technical perspective, microscope resolution is a quantified concept that is defined by the numerical aperture (N.A.) rating of the microscope objective lens. Numerical aperture is a number that expresses the ability of a lens to resolve fine detail in the object being observed.

Magnification is simply how much an image is enlarged.

The images below are the same small printed part with text on it. The first image was captured using a stereo microscope with a lens that has NA 0.10. This image was captured at 90x. It is very hard (in fact nearly impossible!) to read any text on the part in this image. This image also took nearly two hours to capture when trying to get an in-focus, high quality image.

Stereo Microscope Resolution Image

The next image was captured using a metallurgical microscope with a lens that has NA 0.30 and magnification of 100x. This image took only a few minutes to capture. The magnifications of both of these images is very similar however, notice how much easier it is to read the printed letters in the image below that was captured with the metallurgical microscope. This ability to read the letters is due to better resolution, which was obtained beacuse of a higher numerical aperture of the lens used.

Metallurgical microscope image showing resolution and magnification.