A large rose-tree stood near the entrance of the garden: the roses growing on it were white, but there were three gardeners at it, busily painting them red.
Alice in Wonderland
In the previous chapter, we called an image without color “black and white” as used in photography. Here, we shall be introducing the more rigorous term achromatic, derived from the Greek and meaning “colorless.” An achromatic image is an image that appears in shades of neutral gray instead of being in a single spectral hue (“monochromatic”). For transmission images, we shall be using the term white-light transmission (WLT) hologram, as the term “rainbow ...