In a previous article, we discussed the maximum general magnification you can get from a typical light microscope.

If you're interested in useful magnification (the magnification at which you can resolve fine specimen detail with maximum clarity), the value would depend on the objective's numerical aperture (NA). The equation for this is

Maximum useful magnification = 1000 x NA

100x objectives typically go up to 1.40 NA, so the maximum useful magnification achievable today is about 1400x.

However, there are cases when you might want to work outside the useful magnification:

"In practice, magnifications deviating considerably from the useful magnification range are often employed. For example, very low magnifications (1x through 4x) are often used to topographically map a specimen (such as a histologically stained thin section) where a wide field of view is desirable in order to quickly note all available specimen features. In many cases, a 2.5x objective may be combined with a wide field eyepiece at 10x magnification to reveal an area having a diameter of 8 millimeters or greater.

At high magnifications, the limit of useful magnification is sometimes exceeded in order to view the image more comfortably. This is often the case when small particles or organisms are observed and counted at very high numerical apertures and magnifications. Sharpness in the specimen details is then sacrificed, which usually does not interfere with quantitative analysis of the image."

- Kenneth R. Spring and Michael W. Davidson, "Useful Magnification Range," https://www.microscopyu.com/microscopy-basics/useful-magnification-range

Could Advancements in Lens Manufacturing Increase Useful Magnification?

Imagine being able to observe a virus through your household microscope. Maybe you could cure a disease or two?

The conventional microscope's lenses limit the amount of detail you can see in an image. You can see cell walls and chloroplasts, but not ribosomes or DNA molecules.

One way to create a microscope that can resolve detail at the molecular level is to develop a superlens. A superlens employs specially engineered substances called metamaterials to overcome the limitations of conventional lenses, specifically the diffraction limit or diffraction barrier.

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