Lens Selection Tips

How to Select the Right Lens Resolution for Your Application

Choosing the right lens for your application involves matching its resolution and optical format to your target image sensor. A well-matched lens and sensor combination ensures optimal image quality and avoids wasted performance.

1. Lens Resolution vs. Sensor Resolution

When lenses are manufactured, their resolution is usually measured with a lens inspection projector, expressed in lp/mm (line pairs per millimeter). Although manufacturers often label lenses with intuitive ratings like 1MP, 2MP, or 3MP, these are indirect indicators of their resolving power.

The sensor’s Pixel Size determines the physical limit of resolution, known as the Nyquist Frequency. In theory, the smallest resolvable line pair equals twice the pixel size. However, due to Moiré effects at the Nyquist limit, the practical resolution is closer to 0.66 × Nyquist Frequency. This means one line pair should ideally span three pixels, giving the formula:

Pixel Size = 1 / [3 × (lp/mm)]   (Unit: mm)

2. Matching Criteria

• The lens resolution (in line pairs) corresponds to the sensor’s pixel size, following the 3-pixel-per-line-pair rule.
• The lens image circle fully covers the sensor’s size to avoid vignetting or dark corners.

When these two conditions are met, the lens and sensor are optimally matched. Using mismatched components is possible, but may result in reduced image quality or unused sensor area. At IADIY, we help customers choose the most suitable combination to meet their specific application needs.