Well,
I did not leaved it with the wrong look I gave you in the screenshot.
In the documentation it says : If you upload an image with a bigger height than this, it will automatically be scaled to fit.
I uploaded a bigger logo than 42 px, but it does not automatically scale himself, so I have to enter a custom logo height (125 px) in the theme option panel.
Logo Height
Please enter the height of your logo here (standard size). This is optional, and if you do not provide anything here then the logo area height will be restricted to 42px. Numerical value (no px).
So, is it normal that I have to do this?
Many thanks
francois