In general, inherent susceptibility to environmental noise has tended to retard adoption of interference methods by industry. Phase shifting is a key step in optical interference techniques of measurement. An improved max-min scanning (IMMS) method for phase determination was reported in 2004, but the environmental noise tolerance of this approach relative to other methods has been an open question. We discuss the noise tolerance of the IMMS method. Numerical simulations and simple experiments show that the method has good tolerance to some specific environmental vibration inputs, including high-frequency noise and small-amplitude low-frequency noise. The simplified data acquisition and improved noise tolerance of IMMS broadens potential applications of interferometry, particularly digital speckle pattern interferometry in the factory and the field. Another benefit of the IMMS method is an online technique to calibrate and test the phase shifter in real time. This idea is described and demonstrated.