## Useful Magnification Range

Explore the range of useful magnification for common Nikon objective and eyepiece combinations with this interactive tutorial. Users have the ability to select from current optical components as a function of aberration correction through the use of pull-down menus.

To operate the tutorial, first select the objective from the **Choose an Objective** pull-down menu. The list covers all of Nikon's current objectives in the achromat, plan achromat, plan fluorite, and plan apochromat series. Several specialized objectives are included as well. Next, choose the eyepiece magnification from the **Eyepiece Magnification** pull-down menu. The applet will then automatically calculate the useful magnification range based on the objective numerical aperture and magnification and the eyepiece magnification. If the objective/eyepiece value falls within this range, a green checkmark is displayed along with the text: "**In Range**". In situations where the combination does not produce a magnification factor in the useful range, a red **x** is displayed along with the text: "**Out of Range**". It should be noted that out of range values do not necessarily indicate that the selected combination is incapable of performing to the user's specifications.

The **range of useful magnification** for an objective/eyepiece combination is defined by the numerical aperture of the microscope optical system. There is a minimum magnification necessary for the detail present in an image to be resolved, and this value is usually rather arbitrarily set as 500 times the numerical aperture (500 x NA) and defined by the equation**:**

At the other end of the spectrum, the maximum useful magnification of an image is usually set at 1000 times the numerical aperture (1000 x NA) as given by the equation above. Magnifications higher than this value will yield no further useful information or finer resolution of image detail, and will usually lead to image degradation.

### Contributing Authors

**Kenneth R. Spring** - Scientific Consultant, Lusby, Maryland, 20657.

**John C. Long and Michael W. Davidson** - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.

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