Technologies are described for providing optical analysis systems using an integrated computational element that has a surface patterned to selectively reflect or transmit different wavelengths by differing amounts across a spectrum of wavelengths. In one aspect, a measurement tool contains an optical element including a layer of material patterned so that the optical element selectively transmits or reflects, during operation of the measurement tool, light in at least a portion of a wavelength range by differing amounts, the differing amounts being related to a property of a sample. The wavelength range can include wavelengths in a range from about 0.2 μm to about 100 μm. Additionally, the sample can include wellbore fluids and the property of the sample is a property of the wellbore fluids.