exact Geo !
du coup je crois que je vais "décapiter" mon bouchon de biberon, ca laissera échapper la chaleur.
(ceci dit avec le bouchon de bib c'est ouvert par en bas)

Coté "comment/comprendre le flash sur les Canon EOS" j'ai trouvé cet article :
Flash Photography with Canon EOS Cameras - Part II.

Je le trouve vraiment bien.

Le tableau de base à retenir:

EOS flash photography confusion. The main area of confusion in EOS flash photography is the fact that P, Tv, Av and M modes handle flash illumination differently, especially when ambient light levels are not bright. Here’s a summary of how the modes basically work when you have a flash unit turned on. This summary assumes that you do not have high speed sync flash enabled if that option is available to your particular camera and flash unit combination.
Mode Shutter speed Lens aperture
P Automatically set from 1/60 sec to the camera’s maximum X-sync speed. Automatically set according to the camera’s built-in program.
Tv You can set any shutter speed between 30 seconds and the camera’s maximum X-sync speed. Automatically set to match the shutter speed you have set.
Av Automatically set between 30 seconds and the camera’s maximum X-sync speed to match the lens aperture you have set. You can set any lens aperture you like.
M You can set any shutter speed between 30 seconds and the camera’s maximum X-sync speed.