Embodiments relate to using a display and camera of a computing device to perform pulse oximetry. The display of the device is used as an illuminant, a finger is placed over a portion of the display and a camera facing in the same direction as the display. One or more colors are selected to enhance hemoglobin-deoxyhemoglobin contrast in view of display and camera sensitivities. The one or more colors are displayed while a body part covers the displayed color and the camera. The camera captures images of light that has passed through the finger and been internally reflected to the camera. The light reaching the camera has been absorbed by arterial hemoglobin and deoxyhemoglobin at different rates in respective different wavebands. Differences in attenuation of display light at the different wavebands provide sufficient contrast to compute an accurate pulse oxygenation estimate.
