Do I Need a Megapixel Lens?

Pairing the lens performance with the sensor and pixel size is critical.  High resolution sensors are usually not much larger than those used for HD cameras, but their pixel count is significantly higher and the pixel sizes are necessarily much smaller, making the lens’ requirement to resolve the small pixels crucial. 

While a typical HD sensor is 1/2.8” in size with 2.9 micron-sized pixels, one 4K sensor is 1/2.3” in size, with 1.45 micron-sized pixels –50% smaller pixels. One might be tempted to pair the higher resolution cameras with a lens that covers a similar sized but lower resolution sensor. While the lenses required to physically cover both image sensors are similar, the resolving capability required of the higher resolution lenses to pair with the smaller pixel sized sensors is much greater.

In testing, the New Jersey high school determined that using a standard resolution lens with a 5-megapixel camera produced a blurry image.  Most often if you want to take advantage of all the pixels a multi megapixel camera provides, a high-quality lens with matching resolution is needed, otherwise the money spent on a high-resolution camera is wasted. 

When using a megapixel camera it is important that the spot size of the focal plane of the lens used be comparable in size or smaller than the pixel size of the camera, otherwise the light falls off the pixel resulting in a fuzzy image. The spot size is the area where the lens focuses rays of light as illustrated in the images below

A megapixel lens requires more elements, more complex shaped and higher precision elements such as aspheres, making them more difficult to manufacture and more costly to purchase. 

In megapixel cameras the pixel size and the required lens spot size varies depending on the size of sensor and quantity of pixels it contains.  You can have 2 different cameras, both 1.3 megapixel, but if the sensor size is not the same, the pixel size will be different.  The figure below illustrates this. 

In selecting a lens it is important to choose one that is designed for use with the same sensor size or smaller and designated to match or be higher than the megapixel rating of the camera.

Beyond that, not all megapixel rated lenses are created equal and the task of selecting a megapixel lens is complex.