The Histogram

Like other software, PhotoLab’s histogram presents the processed version (current display) of the image according to an 8-bit scale (JPEG compatible), either on 255 values, considering the latter as the “100% brightness” .
When converting to 16 bits, the decomposition of values ​​is much greater.
The maximum brightness is on the 65,536 th section.

* Highlight (Ctrl+ W/ A)and Dark Tone (Ctrl+ B/ B) peuvent être permutés.
* The height of the histogram palette can be changed by clicking and holding the lower part of the histogram (Windows only).

The histogram warnings are basic. If a single channel of a pixel is clipped it is signaled too quickly. It is represented by its reverse color.
This does not make sense especially for a channel at 0.

Click to enlarge – Alt+ < to return

There are false warnings in this photo.
1- Lack of green and blue on a red shirt
2- Lack of blue on the ear! My boy is not a Smurfs 😉

There is also the case of a saturated color where, this time, the risk of clipping is real. You have to use the tone curve to control saturation.
1- Histogram before saturation
2- Histogram after saturation
3- False color warning histogram
4- The histogram shows that the blues are blocked and the reds are burnt
5- Histogram we can adjust the red // green // blue curve

* The raw histogram with its large dynamic range is not accessible. A warning in reverse tone, all black or white (all RGB channels at 0 or 255) does not necessarily mean that there is clipping when shooting, only that there may be clipping.

The Tone Curve

By changing the black point or the white point on the tone curve, the tonal range is only tightened.
Details lost on the raw definition are not recovered with this method. The clipping is carried to lower values, for example 4 and 250. The histogram warnings are inactive but this part of the image, expressed as light gray or dark gray pixels, remains empty of tones.

The tone curve is a poor tool on PhotoLab because the software offers other tools. In fact, it was only designed to increase the action of other corrections.
* Exposure compensation is the best tool for reducing highlights that are not overexposed. You can then curve the tone curve to restore the general impression of luminosity.
* Another avenue is to use Smart Lighting which compresses extreme values. This tool is very good at retrieving details in extreme areas that are apparently clipped.
* Finally, the three selective tone controls achieve the same correction as points placed at the ends and in the middle of the tone curve.
* The Global Contrast slider is equivalent to an ‘S’ shape

Dxo is aware that many users are orphans of a tool that they consider essential. – All rights reserved – tous droits réservés.

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