We study the process of sum-frequency generation of femtosecond laser pulses in a strontium barium niobate crystal with a random distribution of ferroelectric domains. The random domain structure allows for broadband quasi-phase matching of wavelengths over the whole visible spectrum. We analyze sum-frequency generation in the wavelength range 460nm - 630 nm, which is emitted on a cone with angles between 30 • and 55 •. We measure the effective angular width of the sum-frequency intensity profile which is related to the spectral pulse width and directly visualizes the spectral pulse broadening due to self-phase modulation.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.