To my understanding of things, a true B&W sensor would be impossible, just based on how digital technology works. JPEG, for instance, is incapable of storing anything but color images. A B&W conversion merely zeros out some components of the color channels. For example, if you look at component video, the Y (green cable) is the luma channel; it basically carries a black and white copy of the signal. The other two, Cr and Cb (or Pr and Pb for analog) are chrominance channels. Zero those out and you can reduce the image to B&W.
But the issue is all digital images are stored as RGB, not as Y'CrCb. If they were, then we could have actual B&W images. The reason YCrCb (YPrPb) exists is to save cable bandwidth. In an RGB signal, green has the highest amplitude, so you'd need to a high bandwidth cable to carry the signal. This bandwidth is wasted on the less intense B and R signals, so the solution was to take the RGB and split it up more evenly. The result is Y'CrCb.
Even going to CMYK won't help you. We'd need a sensor and image format that capture and store in Y'CrCb. I'm pretty sure that has not been invented yet. It may never be; the interest in a native B&W sensor is limited. It's more effective to improve conversion technology.
Last edited by MadMathMind; 03-05-2014 at 10:38 PM.