Left: single raw image of a target star provided by the SDI mode of NaCo. The wavelength of the four subimages is from the top right in the anticlockwise direction: 1.575, 1.600, 1.625, and 1.625 μm. The image is thresholded and the scale is logarithmic. Right: flat-field image of the SDI filters (the vertical bars of the filter support are visible in the top half of the image), the double Wollaston prism (which produces the four subimages) and the FQPM (the cross visible in each subimage). The image scale is linear. Both image sizes are 1026 pixels × 1024 pixels, and the field of view of each subimage is 8′′ × 8′′. The cut of the images seen on their left side is due to the position of the field selector on the light beam. Note the inverted tints of both images.