Magnification 101

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ErgoPractice News – December 2022
By Jin Chang PhD


Magnification is not complicated. For example, a 2.5x magnification increases the object size two and a half times the size to the naked eye. Loupes are a passive device to help you see in more detail and help you work at a comfortable and safe working distance. 

Being a passive device, there are three major impacts on the magnification from the loupes to your eyes. The distance from the loupe to the object you are working on, the distance from the ocular to your eye, and the design, build, and materials of the ocular.   

Figure 1: Magnifications from 2.5x to 10.0x.

Distance Effect

With an increase in the working distance, an increase in magnification is needed to see the same amount of detail. As shown in Figure 2, a 2.5x magnification with an object 15-inches from you is visually the same size as holding that object 6-inches from your face with the naked eye. At 2.5x and 3.0x when you are working in an upright ergonomic posture, the size of an object is the same apparent size as if you were leaning over in an unsafe posture. With that in mind, if you want to see an object at twice the magnification when compared to a 6-inch working distance you are going to need 4.5x or 5.5x magnification. Then if you want to see an object three times the size, you will need 8.0x or 10.0x magnification. Working distance and distance effect need to be considered when selecting a magnification power.  

Figure 2: The same visual size of an object shown at different magnifications. 

Ocular to Eye 

Image distance, also known as the keyhole effect, allows you to only see part of the full magnified image projected from the back of the ocular. The closer your eye is to the end of the ocular, the more your field of view is affected. This is the main reason why most loupes that we make are through-the-lens, (TTL) style. Our frames are also either selected or designed to have a pantoscopic tilt to bring the ocular closer to your eyes. As a side note, the pantoscopic tilt of the lens helps give an increase in declination angle for a better ergonomic posture and also better eye protection. 

Design, Build, and Materials

Not all loupes have the same quality, design, and build. SurgiTel patented prism loupes are designed to give you the widest field of view, the longest depth of field, and edge-to-edge clarity. All of our loupes are manufactured with premium medical-grade glass with anti-reflective coatings to give the best light transmission and clarity.  

The Effects of Increased Magnification

The last understanding of magnification is the decrease of the field of view and depth of field as you jump to higher-powered loupes. Simply put, as you jump to a higher magnification your field of view and depth of field decrease. The advantage of wearing loupes is that you are able to move your head freely around the operating area to bring objects into focus. 

Figure 3: Depth of field and field of view comparisons.


Learn More 

If you are interested in learning more we recommend these more in-depth newsletters.

SurgiTel offers a wide range of magnifications with optimal design and quality to provide clinicians with the best vision and ergonomics. Take the next step to increase your magnification and improve your ergonomics click here to schedule a free in-person appointment.