Steve Spencer
Online
• • • • • • •
Upload & Sell: On
|
 p.14 #5 · After 13 years of all Sony, I'm trying Nikon | |
ruthenium wrote:
Steve, you make a good point here. Thus, the question is "what does the term 'tonal gradations' mean?"
Chat GPT, conveniently supplies the following:
"👉 Tonal gradations refer to the smooth, gradual transitions between different tones — usually shades of light and dark, or subtle differences in color or brightness.
For example:
In a black-and-white photograph, tonal gradations are the smooth changes from pure black through many shades of gray to pure white.
In a painting or digital image, tonal gradations describe how one color blends gradually into another"
The first of the two meanings is what we normally think of as the Dynamic range. A large DR means many numbers in the ADC (analog-to-digital converter) range between black and white. This allows very subtle changes in the tones in-between. In other words, a large DR allows distinguishing very subtle changes in light levels (light intensity).
The second meaning of the "tonal transitions" is about the color depth, and I think this is a closely related idea. Let's recall that all colors result from mixing R-G-B. The jpegs, for example, have an 8-bit color depth, meaning that a certain color is defined by a combination of three numbers, each ranging from zero to 255. For black-grey-white tones:
Pure black: 0,0,0
Dark grey: 50,50,50
Middle grey: 128,128,128
Light grey: 200,200,200
Pure white: 255,255,255
Thus, a camera sensor can only register the intensity of light, not colors. It is the information about which numbers come from under red, green, or blue microlenses that allows the synthesis of the colors.
There are photographers who have much better understanding of DR than mine, but I think the tonal gradations in both senses are indeed directly linked to the DR of a camera sensor. ...Show more →
Hi Dimitri,
I am not sure color depth is related to DR directly as it is likely affected by the color filter array and post processing. When DXO measures color depth they no doubt are using their own software for the RAW conversion and I believe they are analyzing the colors that come out of their RAW conversion. It is quite possible that a different RAW converter would get different numbers. So what DXO is measuring as color depth is that light intensity under Red, Green, and Blue pixels as interpreted by their RAW converter. Certainly more light intensity will mean better colors, but the filter array will play a role as will the RAW conversion, I believe. And DR is not simply light intensity.
From a causal modeling point of view, I suspect that light intensity leads to DR and light intensity also leads to color depth, so DR and color depth will be correlated with each other but not causal related and I further suspect that a given color array may have to make tradeoffs between DR and color depth. Increasing DR by lightening the intensity of the color filtration might well lead to less color depth. So, it is possible that even though DR and color depth are correlated increasing one from an engineering standpoint can come at the cost of increasing the other. Some things like increasing light intensity will improve both, but that doesn't mean they are causally related.
|
...
.
