The combination of color schlieren with high speed flash techniques has proved to be a valuable tool for investigating high speed transient events. Fully two dimensional refractive index information can be ob­ tained. The resolution on 35 mm film was sharp enough to allow 50 cm by 75 cm color enlargements. REFERENCES 1. Barnes, N.F., Jour. of the SMPTE, Oct. 1953, Vol. 61,487-511. 2. Cords, P.R., S.P.I.E. Jour., February-March 1968, Vol. 6. 3. North, R.J., NPL/Aero/266, 1954. 4. Settles, G.S., Image Technology, June-July 1972. 5. Smith, L.L., and J.R. Waddell, 9th Congress of Righ Speed Photogra­ phy, Denver, Colo., August 1970, Paper 86. 6. Stong, C.L., and G.S. Settles, Scientific American, May 1971, Vol. 225, No.5. 7. Stong, C.L., and Vandiver, J.K., Scientific American, August 1974, Vol. 231, No.2. ,105 DISCUSSION MY' R J North, (UK): Pould the author care to comment on possible ambiguities of interpretation due to the omnidirectional sensitivity of the colour filter system used? I notice that in two of his pic­ tures density gradients in directions at right angles are shown by the same colour transitions. MY' J Kim Vandiver: The photographs presented were not composed to yield accurate determination of the direction of density gradients.