Louis Ducos du Hauron had suggested using a sandwich of three differently color-recording emulsions on transparent supports which could be exposed together in an ordinary camera, then taken apart and used like any other set of three-color separations. The problem was that although two of the emulsions could be in contact face-to-face, the third would have to be separated by the thickness of one transparent support layer. Because all silver halide emulsions are inherently sensitive to blue, the blue-recording layer ought to be on top and have a blue-blocking yellow filter layer behind it. This blue-recording layer, used to make the yellow print which could most afford to be "soft", would end up producing the sharpest image. The two layers behind it, one sensitized to red but not green and the other to green but not red, would suffer from scattering of the light as it passed through the topmost emulsion, and one or both would further suffer by being spaced away from it.