Let me now ask a real newbie question : is there a way, i didn't discover, to render any image as tiff ? PNG is a lot better as JPG, but for the very big formats TIFF would be great.
No, there is no option to render as TIFF, I'm afraid - just JPEG, PNG and TGA. I'd recommend saving as PNG then convert to TIFF with ImageMagick or GIMP.
Thank's really : TGA seems exactly what i searched, i.e. an uncompressed format. Maybe better as TIFF itself ?