Increasing fuel injection pressure has enabled reduction of diesel emissions while retaining the advantage of the high thermal efficiency of diesel engines. With production diesel injectors operating in the range from 300 to 2400 bar, there is interest in injection pressures of 3000 bar and higher for further emissions reduction and fuel efficiency improvements. Fundamental understanding of diesel spray characteristics including very early injection and non-vaporizing spray penetration is essential to improve model development and facilitate the integration of advanced injection systems with elevated injection pressure into future diesel engines. Studies were conducted in an optically accessible constant volume combustion vessel under non-vaporizing conditions. Two advanced high pressure multi-hole injectors were used with different hole diameters, number of holes, and flow rates, with only one plume of each injector being imaged to enable high frame rate imaging. These injectors were studied between 2000 and 3000 bar injection pressures with ultra-low sulfur diesel fuel. The study included two part-load charge density conditions of 7.4 kg/m3 and 14.7 kg/m3 along with an elevated density boosted condition of 34.8 kg/m3. Diagnostics used included Mie backscatter imaging for liquid phase penetration. Experimental results of spray penetration were fit to an enhanced penetration correlation to represent the distinct phases of the injector opening and spray development. The spray penetration results were also compared to rate of injection data for the injectors to further understand and characterize the spray development process very early in the injection. The analysis and results provide a method of fitting and quantifying spray penetration with a revised correlation and for improved understanding of dynamics occurring in the injector the influence of elevated injection pressure on fundamental spray characteristics.