such as those described in @Hall.2002. However, those objects can be differenciated from brown dwarfs using only photometry: they are not as red in $i'-z'$ as ultracool brown dwarfs and will appear in the $i'$ CFBDS images whereas brown dwarfs will not. Quasars with redshift z$>$7 cannot be distinguished from cool brown dwarfs using the CFBDSIR $i',z',J$ and optical photometry, but we would be lucky to find just one of these extremely interesting objects. None has been discovered yet, and extrapolation of the z$=$6 luminosity function [@Willott.2010] suggests that wider or/and deeper surveys will be needed to find one. Other possible contaminants are detector artefacts and variable objects whose luminosity changed between $z'$ and $J$ exposures.

The survey
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[**WIRCam NIR data.**]{} This article focuses on the results obtained from a 66 square degrees pilot subset of CFBDSIR whose final coverage is expected to be 335 square degree. CFBDSIR WIRCam imaging goes to a depth of $J_{vega}=20.0$ for a point-source detection limit of 10$\sigma$, which ensures accurate photometry and rejects most spurious detections. Images were acquired at CFHT in QSO mode with seeing varying from 0.6to 1.0during semesters 2006B, 2007A, and 2009B. These WIRCam images overlap the existing $z'$-band images 