2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/124241It has been traditionally stated that it is not possible to use optical/NIR photometry to measure the temperatures of O stars. In this contribution we describe the steps required to overcome the hurdles that have prevented this from happening in the past and we present our preliminary results for the low-extinction case.2 pages, to appear in Massive Stars: Fundamental Parameters and Circumstellar InteractionsAstrophysicstext