A fluidic structure includes a channel and along the channel is a series of sensing components to obtain information about objects traveling within the channel, such as droplets or other objects carried by fluid. At least one sensing component includes a set of cells of a photosensor array. The set of cells photosense a range of photon energies that emanate from objects, and include a subset of cells that photosense within subranges. A processor can receive information about objects from the sensing components and use it to obtain spectral information. The processor can perform an initial analysis using information from one set of sensing components and, based on the results, control a fluidic device in the channel, such as a gate, to retain objects, such as for concentration and more detailed analysis by other sensing components, or to purge objects from the channel.