Hey Etienne,
Nice to see you here also,
I talked to Iridas, and I heard that they are planning on a new set of LUT's for Alexa soon ( IBC starts on 10 Sept) that should fix that issue.
If you and Jay would send me a private message the Arridigital forum with your email addresses- I will send both of you the rough ones I built I have quickie Day and Night versions that are not full REC709 compliant.
gary adcock
Studio37
Post and Production Workflow Consultant
Production and Post Stereographer
Chicago, IL
http://blogs.creativecow.net/24640