About the cause of Nikon yellow

Used D70s,d80, and then use the D90, at first glance, the color is much brighter. and directly out of the picture seems to be a lot brighter than the original. However, portrait complexion is sallow (not only white balance problem, but also color tendency and brightness), emerald green is yellow, red is saturated and loses level.
Among them, portrait photography is particularly troubling. The concrete manifestation is,
First, high-gloss area contrast is not high, the characters face the whole side of the cake.
Second, the yellow saturation of the screen is high, and the yellow brightness is lower, resulting in liver color.

Play NX2 half a year, finally found the reason for the sallow, that is because the curve of the mud, pulled in the LCH color space!
Previously noted that when decoding D80 Nef file, if the use of optimal calibration, compared to the selection of optimal calibration, exposure to add 0.3EV. Yesterday suddenly a whim, in the Nikon software inside there are custom curves. We choose a custom curve based on "standard" mode, the default is a straight line, then the resulting image is not the same as the original standard brightness, standard contrast. Then found that the photo went dark, but the leaves, safflower, natural color appeared. In fact, the mud pits in all modes (landscape, vivid, portrait ...) ), all artificially pulled a curve of its own. The gamma of this curve is about 1.10, but not a standard gamma curve. I think this curve is the culprit that causes the color distortion of the object.

Children who have played the lab mode in Photoshop know that the lab mode is completely independent of brightness and color, and adjusting the lightness of L does not affect the hue and saturation of the color. This is different from RGB mode, where the saturation of one pixel is reduced when the curve is highlighted. Also, there will be a certain change in hue.

Can do an experiment, casually find a normal portrait, if you brighten the L channel in lab mode, you will find that strange wax yellow appeared! Why is this?
That is because, in the correct natural exposure, the saturation of the dark color will be stronger, and the saturation of the light will be relatively low. Put on the face, that is, the light saturation of the face is much higher than the dark part. So, what happens if we go to the pull curve? When the face is in the middle and high light area, the light difference between the dark part of the face and the bright part becomes less obvious. However, the saturation of the dark part remains the same, much higher than the light, so the yellow of the darker part of the face becomes a bright, high-saturation yellow, and the feeling of wax appears. In the normal exposure, if we increase exposure, we will find that the face of the dark and the saturation of the light will be diluted, which is more similar to our drawing curve in the RGB space, so in the RGB under the brightness of the portrait, it is more natural.

LCH color space and lab space homology, h represents brightness, equals l, while s,b corresponds to hue and saturation. Only lab uses a Cartesian coordinate system to represent color and saturation, while in lab it uses polar coordinates.

So, in order to please the eye, so that all the color becomes bright and bright, regardless of the true brightness and saturation of the relationship between. This may be good when shooting landscapes, but as I can only say ...

To remove this unnatural wax sensation, please: Pull the curve Down under the lab or LSB and then go back to RGB mode to brighten.

Then, talk about the optimal calibration.
I will standard, natural, landscape, bright and colorful optimization calibration all custom curves, straighten.
It was then found that even though the curve was also a straight line, the default processing gave different results for color and contrast.

Standard, corresponding to IA, moderate saturation contrast, slightly enhanced color.
Natural, corresponds to II, saturation contrast low, color natural but some yellow.
Landscape, corresponds to IIIA, high saturation contrast.
Portrait, in fact, is natural, but more than the natural mode, the saturation of the red color has a certain increase, this in Lightroom we know that the saturation and brightness of the three primary colors can be arbitrarily adjusted.

I downloaded the three curves directly into the camera. Then found that the real feeling of d70s,d80 back, the picture is still a little yellow! But everything else is a little bit more natural.

The mire why this, in fact, also makes sense, is to provide more dark details.
We know in the d70s,d80 that there is an exposure tendency in the mud, dark 0.3eV to protect the high light.
D90, in fact, in the custom curve as a straight line, but also the same as D70S,D80.
Since JPG is the linear data into non-linear data with respect to raw, the difference in the dark and the details in the conversion to JPG, all are compressed to 1-10 of the brightness range, it will result in the loss of detail, so the mire artificially pull the high curve to protect the details. So the details will be more, documentary theme needs.

If I use a straight line like this, then the film straight out is not good to see, but also to be a bright.
So, when considering this point, Nikon, for the positioning of the low-end SLR, he knows a lot of users are only transferred from the digital DC, accustomed to the small DC automatic optimization. So still light some, people face acne will be less, face, rookie also no matter too much is not it.

Then, for me, later, either use raw, or use natural mode (straight version), and then go to the yellow, such as with the Hue tool in LCH, orange to red, yellow green to the green to compress the yellow range, and then lower the yellow saturation, improve brightness.

Or use the optional color yellow to Huanggazing, and the lab mode to adjust. In short, it is a very troublesome thing. There is no way, the bed is sharp high, more details, this is my choice of mud is an important reason. Color Let it go with the wind.

Reasons for Nikon Yellow