The detection and characterization of extrasolar planets by direct imaging is becoming more and more promising with the preparation of dedicated high-contrast instruments and the help of new data analysis techniques. SPHERE (Spectro-Polarimetric High-contrast imager for Exoplanets REsearch) is currently being developed as part of the second generation instruments of the ESO-VLT. IRDIS, one of the SPHERE subsystems, will provide dual-band imaging with several filter pairs covering the near-infrared from 0.95 to 2.3 microns, among with other observing modes such as long slit spectroscopy and infrared polarimetry. This paper describes the instrument performances and the impact of instrumental calibrations on finding and characterizing extrasolar planets, and on observing strategies. It discusses constraints to achieve the required contrast of ~106 within few hours of exposure time.