How to Choose an Imaging Lens

The figures below show Horizontal Field of View (FOV) vs. Working Distance (WD) for four different sensor sizes: 1/3”, 1/1.8”, 2/3”, and 1”. By first selecting a sensor size and then finding the Horizontal FOV and WD required on the plot, the appropriate focal length of the imaging lens that will work for your application can be determined.

Important Considerations for Choosing an Imaging Lens:

• Longer focal length lenses have longer minimum working distances, which is a consequence of their optical designs. Minimum working distance can be shortened by adding spacers between the lens and camera, but image quality will eventually suffer.
• Larger sensors provide larger FOVs with the same focal length lens. For example, at a working distance of 350mm, a 12mm lens on a 2/3” sensor will have an FOV of about 370mm, but on a 1” sensor at the same working distance, the field of view is approximately 530mm - an increase of 43%.
• There are gaps in the plots, indicative that a standard off-the-shelf fixed focal length lens does not exist. For example, it is impossible to achieve a 525mm field of view at a 600mm working distance with a 2/3” sensor with available focal lengths. The closest lens that exists is an 8.5mm focal length, which would need to be used at a working distance of about 510mm to achieve that field of view.

Figure 1: These plots are based on TECHSPEC^® C Series Fixed Focal Length Lenses. However, these plots can be applied to any lens and are not limited to only the TECHSPEC^® C Series Lenses.