Category: reference

locationtextures.com/

kitbash3d.com

https://www.quora.com/What-is-the-comparison-between-the-human-eye-and-a-digital-camera

https://medium.com/hipster-color-science/a-beginners-guide-to-colorimetry-401f1830b65a

There are three types of cone photoreceptors in the eye, called Long, Medium and Short. These contribute to color discrimination. They are all sensitive to different, yet overlapping, wavelengths of light. They are commonly associated with the color they are most sensitive too, L = red, M = green, S = blue.

Different spectral distributions can stimulate the cones in the exact same way
A leaf and a green car that look the same to you, but physically have different reflectance properties. It turns out every color (or, unique cone output) can be created from many different spectral distributions. Color science starts to make a lot more sense when you understand this.

When you view the charts overlaid, you can see that the spinach mostly reflects light outside of the eye’s visual range, and inside our range it mostly reflects light centered around our M cone.

This phenomenon is called metamerism and it has huge ramifications for color reproduction. It means we don’t need the original light to reproduce an observed color.

http://www.absoluteastronomy.com/topics/Adaptation_%28eye%29

The human eye can function from very dark to very bright levels of light; its sensing capabilities reach across nine orders of magnitude. This means that the brightest and the darkest light signal that the eye can sense are a factor of roughly 1,000,000,000 apart. However, in any given moment of time, the eye can only sense a contrast ratio of one thousand. What enables the wider reach is that the eye adapts its definition of what is black. The light level that is interpreted as “black” can be shifted across six orders of magnitude—a factor of one million.

https://clarkvision.com/articles/eye-resolution.html

The Human eye is able to function in bright sunlight and view faint starlight, a range of more than 100 million to one. The Blackwell (1946) data covered a brightness range of 10 million and did not include intensities brighter than about the full Moon. The full range of adaptability is on the order of a billion to 1. But this is like saying a camera can function over a similar range by adjusting the ISO gain, aperture and exposure time.

In any one view, the eye eye can see over a 10,000 range in contrast detection, but it depends on the scene brightness, with the range decreasing with lower contrast targets. The eye is a contrast detector, not an absolute detector like the sensor in a digital camera, thus the distinction.  The range of the human eye is greater than any film or consumer digital camera.

As for DSLR cameras’ contrast ratio ranges in 2048:1.

(Daniel Frank) Several key differences stand out for me (among many):

• The area devoted to seeing detail in the eye — the fovea — is extremely small compared to a digital camera sensor. It covers a roughly circular area of only about three degrees of arc. By contrast, a “normal” 50mm lens (so called because it supposedly mimic the perspective of the human eye) covers roughly 40 degrees of arc. Because of this extremely narrow field of view, the eye is constantly making small movements (“saccades”) to scan more of the field, and the brain is building up the illusion of a wider, detailed picture.
• The eye has two different main types of light detecting elements: rods and cones. Rods are more sensitive, and detect only variations in brightness, but not color. Cones sense color, but only work in brighter light. That’s why very dim scenes look desaturated, in shades of gray, to the human eye. If you take a picture in moonlight with a very high-ISO digital camera, you’ll be struck by how saturated the colors are in that picture — it looks like daylight. We think of this difference in color intensity as being inherent in dark scenes, but that’s not true — it’s actually the limitation of the cones in our eyes.
• There are specific cones in the eye with stronger responses to the different wavelengths corresponding to red, green, and blue light. By contrast, the CCD or CMOS sensor in a color digital camera can only sense luminance differences: it just counts photons in tens of millions of tiny photodetectors (“wells”) spread across its surface. In front of this detector is an array of microscopic red, blue, and green filters, one per well. The processing engine in the camera interpolates the luminance of adjacent red-, green-, or blue-filtered detectors based on a so-called “demosaicing” algorithm. This bears no resemblance to how the eye detects color. (The so-called “foveon” sensor sold by Sigma in some of its cameras avoid demosaicing by layering different color-sensing layers, but this still isn’t how the eye works.)
• The files output by color digital cameras contain three channels of luminance data: red, green, and blue. While the human eye has red, green, and blue-sensing cones, those cones are cross-wired in the retina to produce a luminance channel plus a red-green and a blue-yellow channel, and it’s data in that color space (known technically as “LAB”) that goes to the brain. That’s why we can’t perceive a reddish-green or a yellowish-blue, whereas such colors can be represented in the RGB color space used by digital cameras.
• The retina is much larger than the fovea, but the light-sensitive areas outside the fovea, and the nuclei to which they wire in the brain, are highly sensitive to motion, particularly in the periphery of our vision. The human visual system — including the eye — is highly adapted to detecting and analyzing potential threats coming at us from outside our central vision, and priming the brain and body to respond. These functions and systems have no analogue in any digital camera system.