In these experiments, we used a Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) Brilliant (Quantel Laser, France) laser to generate a PA marker on various materials. We used different combinations of wavelengths (532 and 1064 nm) and energy densities (, 19, 64, 172, and ) with specifics for each experiment indicated in Sec. 3. These values do not represent the lowest possible energy necessary to generate a PA signal on our materials. We chose these values to give our PA images a sufficient signal-to-noise ratio (SNR) without having to average over multiple frames. The SNR for some sample images can be seen in Table 1. The images are first normalized and then the SNR is computed as the mean of the foreground divided by the standard deviation of the background, where the foreground and background are separated by a threshold described later. It should be noted that the maximum permissible exposure (MPE) is for 532 nm and for 1064 nm as calculated from the IEC 60825-1 laser safety standard18 based on a 0.25 s exposure time, a 4 ns pulse width, and a frequency of 10 Hz. We used a SonixCEP US system and a 4DL14-5/38 US transducer developed by Ultrasonix Medical Corporation (Richmond, Canada) to scan the volume of interest. This US transducer has a motor that actuates a linear US array to move angularly around an internal pivot point. This US transducer has a bandwidth of 5 to 14 MHz and the linear array is approximately 38 mm in length. The Sonix DAQ device, developed by the University of Hong Kong and Ultrasonix, and the MUSiiC toolkit19 are used to acquire prebeamformed radiofrequency (RF) data from the US machine. The k-wave toolbox16 in MATLAB (Mathworks Inc. Natick, Massachusetts) is used to beamform and reconstruct PA images based on the prebeamformed RF data. For our SC setup, we used a custom system containing two CMLN-13S2C cameras (Point Grey Research, Richmond, Canada) to capture images at 18 Hz. A camera calibration process using the Camera Calibration Toolbox for MATLAB20 generates a calibration file for our SC setup. These calibration files contain the SC setup intrinsic parameters to do 3-D triangulation. We created several phantoms for these experiments: a synthetic phantom made with plastisol and black dye, an ex vivo liver phantom made with gelatin and a freshly resected porcine liver, an ex vivo kidney phantom made with gelatin and a freshly resected porcine kidney, and an ex vivo fat phantom made with gelatin and porcine fatback. The surface of the ex vivo tissue or fat is exposed from the gelatin.