Optical Considerations: Sharpness
Sharpness is often the most important factor in an imaging system. It is the variable that determines the resolving power of the system. It is often in terms of mm/pixel.
The sharpness is much higher in a water-corrected lens. Sharp images have more detail, which is particularly important for any application requiring data processing such as photogrammetry, 3D modelling and machine vision.
At SubC Imaging, we run every single optic through comprehensive lens analysis software. The image on the left is of a flat port lens and the image on the right is of a water-corrected lens.
Flat port lenses have a uniform decrease in sharpness from the center to the edges.
The edges have a MTF < 0.1
Water-corrected lenses create a more even sharpness across the lens system.
The edges are approx. MTF = 0.2
The higher the value of sharpness, the more detail in the image. You can see, with a flat port, the image sharpness is lower as you go from the center of the lens to the edge. The effect is still present with corrected optic, because it is an inherent effect in all lenses, but the overall sharpness is evened out across the whole image.