My Autopano Pro forum

Function                 Icon                           History
Levelling of image    'Automatic horizon'       'Automatic horizon'
Colour levels           'Levels'                        'Levels'

I think this is the best alternative. It clearly keeps them apart. It might be good to clarify it even more with:

Function                 Icon                           History
Levelling of image    'Automatic horizon'       'Automatic horizon'
Colour levels           'Colour levels'                        ' Colour levels'

It looks like peoples don't agree about what is or is not the horizon (the skyline or not the skyline, the "camera horizon" where the points which are the same height  than the lens are located in the subject, etc.)

Since John Houghton (who wrote the tutorial LEVELLING A PANORAMA IMAGE WITH PTGUI http://homepage.ntlworld.com/j.houghton/levtut.htm said "there is no horizon in your image" while the French sentence "l'emplacement de l'horizon est correct" was true, I'm very cautious about that word! This is the reason I made two proposals.

Besides that, the concerned tools are changing "the pitch and the roll" of the stitched image at the same time. When the pano is leaning toward the right or the left (roll) this is corrected.  When the slope looks wrong and an upward or downward change (pitch) is needed this is corrected. Saying this is related to the location of the 3 kinds of horizons defined there http://en.wikipedia.org/wiki/Horizon is not dumb!

[bo] wrote:

In that context, the button is more of a "Try to level the panorama"...

Alexandre explaining when the "leveling button" works and when it can't would probably help.

From experience:
1) my panohead bubble being centered is enough for a lower than one degree error.
2) when using a tripod and no panohead my main care was to set the legs so that the central column was really vertical (I found an easy way for that but don't know how to describes it in a few words.)
3) when shooting hand held it depends of luck (but some training helps.)

Using the Verticals tool is easy when there are several large and well spaced vertical lines in the subject.  Using a larger than 800x400 preview quality often helps.  For some landscapes this Verticals tool is completly helpless.  Besides the well known seaside skyline, using horizontal lines is to be avoided : the word horizontal is very ambiguous - the horizontal lines to be used are those which are parallel to the camera sensor when shooting!

Using the Center point is easy when you can place it on something being at the exact same height the camera was (this is on the skyline only when at the seaside.)

In english :

Function                 Icon                           History
Levelling of image    'Automatic horizon'       'Automatic horizon'
Colour levels           'Colour levels'                'Colour levels'

In french :

Function                 Icon                           History
Levelling of image    'Horizon automatique'    'Horizon automatique'
Colour levels           'Niveaux'                     'Niveaux'

Okay for everyone ?

Even if horizon seems dumb to use, I would prefer to use it against levelling because it's more clear in both language. Now, I must admit, I'm not a linguist.

I suspect this one being the other one !

Done