Right click on both histograms shows a menu where histogram mode can be selected

Zone selection for white balance and lighness adjustment must be done before 
pressing the "select on spot" button, So:
- select the "spot" cursor mode (second button from the upper right)
- trace your spot on the image
- press the spot button

The despeckling section contain three buttons to see single red, green and
blue channels in grayscale. This feature can be can be useful by itself.

Lightness adjustment is a powerful tool to modify the luminosity of a specific 
color on your image. After selecting a spot you can add an adjustment section
by clicking on the "select on spot" button in the "lightness adjustment" section.

The input curve acts before the exposure setting. The "luminosity and saturation" 
curve acts after, so autmatic adjustment of exposure, if engaged, will be
modified by the first, not by the latter.

Adjustment section are more or less in a operational order, so every setting
will be influenced by the previous ones and will influences the following.

Both curves uses the same format, file are interchangeable

Lens correction support for your camera/lens does not depend by nufraw itself.
Ufraw uses lensfun library for this function. Update lensfun and recompile 
nufraw for the last support.

Live histogram and value table shows the value from the cropped area of the image.
To analyze image details the crop cursor can be used to select an image portion.

If your camera has some hot pixels a darkframe can be use to fix it.
Darkframe is subtracted by current image. A darkframe is a simple photo 
of a dark background (for example with the cap on the lens).
Darkframe can be used to reduce thermal noise in very long exposures.
In this case a darkframe should be captured for every image with the same 
exposure time.

Everytime a new image is opened (from the raw file, not from the .nufraw file")
the user default adjustments are applied. The user default settings are
saved everytime a image is saved. The "Save image default" in option window can 
be used to modify this behaviour:
- always: is the starting setting (save defaults on every save action)
- just this once: save default just with the curent image 
- never again: don't save default hereafter

About adjustment:
- using the file chooser an image will be opened with the same adjustments of 
  the previous one
- the first image of the session will be opened using user default
- pressing the reset button the user can:
  - apply the user default to the current image
  - apply the program default (mainly oll zeros) to the current image
  - apply an arbitrary adjustment from a .nufraw file to the current image
- on the option window current adjustments can be saved as user default

