Sharpness vs MicroContrast
A lens or sensor can be sharp without having microcontrast — and it can have microcontrast without being sharp.
Sharpness is the ability to discern fine details, regardless of contrast.
Microcontrast is the ability for one area of the image to maintain strong tonal variation relative to the adjacent areas of the image.
Consider this image of a bit of text. This text is both sharp — you can discern the individual letters, and has micro-contrast — there are areas that have high tonal variation.
But what if we were to take a photo of it from far away and had to enlarge that photo — what would that photo look like.
This image is “sharp” because you can discern the letters. This image also has low micro-contrast because adjacent areas do not maintain tonal independence.
On the other hand, this image is not sharp — you cannot discern the individual letters, however, this image has high microcontrast — sharp borders are maintained between areas of different tonal values.
And this image has both high sharpness and high microcontrast. You can both discern the individual letters (sharpness) and there is a relatively strong difference in tonal values between different sections of the image.
Depending on your personal tastes, an image may be better for having high sharpness or high microcontrast. In an ideal world, we would have both, but in the real world — we often have to choose either one or the other.
Real World Example
The image on the left was shot on a Sigma Merrill series camera, known for their high microcontrast. The image on the right was shot on a Sony A7R2, a 42 megapixel camera, known for its sharpness.
100% Crops — specific details below image.
The Sigma camera (left) has more microcontrast — each eyelash stands in stark contrast to the surrounding area. Skin has a strong texture that you can almost feel.
The Sony (right) is sharp, but has less microcontrast — you can feel how thin each eyelash is, but it doesn’t “pop”. The skin texture isn’t as pronounced, though some of this is down to the depth of field.
Look at the bottom rim of the eyelid — the Sigma feels very much like it’s there. On the Sony the difference between eyelid and eye is a little blurry. The Sigma has more microcontrast — each pixel is distinct from the one next to it.
If you stare at it long enough, the Sigma is a little bit pixellated looking compared to the Sony.
These were both shot from about mid torso up, with the Sony being framed maybe a bit wider than the Sigma, so these are extreme crops. The Sigma was also exported using “double” output size — which turns the 15 megapixel image and doubles both dimensions to 60 megapixel size. At normal export sizes, the microcontrast is even better.
This photo (unedited) should give you a sense of how cropped in these images are.
Foveon Merrill Example
This photo is both sharp (you can count the individual eyelashes) and has microcontrast (pixels stand as distinct from one another without blending together). It maybe loses a little sharpness in the eyebrows (all of the images do), and if there was a section of just hair, you might not be able to count individual hairs — that would be a loss of sharpness (but not microcontrast).
You can imagine that a higher resolution sensor — this is only 15 megapixels — could discern each individual eyebrow hair. Maybe a 60 megapixel or 100 bayer sensor, but I doubt it would have as much microcontrast.
