but formula_9 is the f-number of a lens. A typical setting for use on an overcast day would be (see Sunny 16 rule). For violet 380-450 nm the shortest wavelength visible light, the wavelength λ is about 420 nanometers (see cone cells for sensitivity of S cone cells). This gives a value for formula_6 of about 4 µm. In a digital camera, making the pixels of the image sensor smaller than half this value (one pixel for each object, one for each space between) would not significantly increase the captured image resolution. However, it may improve the final image by over-sampling, allowing noise reduction.