The diffraction limit depends on the f-number of the lens and the wavelength of light being imaged.
In essence, the diffraction limit represents the best possible resolution that an optical system, like a camera lens, can achieve. It's a fundamental physical constraint that arises from the wave nature of light. When light passes through an aperture (like the lens opening), it spreads out, a phenomenon known as diffraction. This spreading blurs the image, limiting the level of detail that can be resolved.
Here's a breakdown of the factors:
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F-number (f/#): This value describes the ratio of the lens's focal length to the diameter of its aperture. A smaller f-number (e.g., f/2.8) indicates a wider aperture, which generally leads to less diffraction and thus better resolution, theoretically. However, very small f-numbers can introduce other optical aberrations. A larger f-number (e.g., f/16) means a smaller aperture, increasing diffraction and reducing resolution.
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Wavelength of Light (λ): Shorter wavelengths of light experience less diffraction than longer wavelengths. This is why ultraviolet microscopes can achieve higher resolution than optical microscopes that use visible light. For visible light, blue light has a shorter wavelength than red light and therefore diffracts less.
Therefore, understanding these two factors enables a photographer to predict the maximum level of detail their lens will be able to capture. It highlights that resolution isn't solely dependent on sensor megapixels but also on the physical properties of light and the lens itself.
