In the paper the results of a comparative analysis of the changes in the fuel spray shape, penetration and its angle in the piezoelectric injection have been discussed. The results of the observation of the fuel (bio-diesel) spray with the use of high-speed camera (100 μs frame frequency) have been presented. The tests were performed for a multi hole piezoinjector and each time the whole fuel spray was observed and analyzed. The injector was placed in a closed chamber with an adjustable backpressure in the range of 0-4.5 MPa. At this stage of the research the authors investigated the influence of the chamber backpressure on the fuel spray shape, atomization and spray front displacement. Moreover, the parameterization and digital processing (including automation) of the obtained images have been presented, too. The influence of the pressure and the timing of the injection on the variable-in-time spray parameters have been shown. The analysis of the B100 fuel spray penetration indicates there is a lack of uniformity in the fuel atomization by all injection holes of a piezoelectric injector. We obtain spreads of the values from 15 to 20% depending on the fuel atomization time counting from the onset of the injection. The heating of the B100 fuel results in a growth of the fuel spray penetration by approximately 30% in the initial phase of the injection. The growth of the said area reaches a maximum value at the end of the injection and amounts to approximately 15%. The value is independent of the injection pressure and injection time.