Why more pixels do not always mean a clearer picture
In short: We often assume a higher megapixel count guarantees superior detail. However, resolution is not merely a tally of pixels, but a complex interplay of light diffraction, lens quality, and pixel size. Understanding this distinction reveals why a smaller, high-density sensor can actually outperform a much larger one.
At its core, optical resolution is the ability of an imaging system to distinguish two separate points as individual entities. While we often focus on the sensor, the limit is frequently set by physics itself through diffraction. When light passes through a lens aperture, it forms an Airy pattern—a central bright spot known as an Airy disk surrounded by concentric rings. According to the Rayleigh criterion, two points are considered resolved when the center of one disk overlaps with the first dark ring of the other.
The quality of a lens determines how close a system comes to this theoretical 'diffraction-limited' ideal. While high-end lenses minimize aberrations, the diameter of the aperture remains a critical lever; larger apertures, such as those found in astronomical telescopes, allow for much finer detail. Beyond the lens, the sensor's architecture plays a decisive role. The Modulation Transfer Function (MTF) describes how well a system preserves contrast at different spatial frequencies. In modern digital sensors, smaller pixels can actually result in wider MTF curves, enabling the detection of higher-frequency energy.
This leads to a common misconception regarding megapixel counts. Because sensors vary in physical dimensions, a 2-megapixel camera utilizing 20-micrometre-square pixels may actually possess worse resolution than a 1-megapixel camera using much smaller 8-micrometre pixels. True resolution depends on the density and the ability of the detecting elements to resolve spatial differences in electromagnetic energy, rather than the sheer number of pixels on the chip.
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- Summary by Intellect · source: Optical resolution
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