La Dentellière stamp

This stamp comes with 3 (maybe 4) color variations - which are regarded as defects. Green, Orange, Yellow, and perhaps Brown tinted. For the examples in my collection, the orange is rather obvious, and the green can be seen best when you hold the stamp to the light and tilt it a bit. The yellow isn't too discernable. So I did color histograms of the normal and 3 variations in Photoshop, and show them to the right of each example. I only did the histograms for the picture part of the stamps, not the black and white borders. I did have to include a fake solid black border for normalization, visible in channel 1 - this normalization is the same for each image.

These are all RBG images. For fully saturated primary colors, Blue + Red = Magenta. Blue + Green = Cyan, and Red + Green = Yellow. In the color combinations histograms below, the combinations substitute for the primaries when they overlap, giving an idea of the average content of the photo in terms of fully saturated colors. This is a simplification - keep in mind there is a large range of colors depending on the amount of the primaries being combined. So the "Yellow" stamp at the end may or may not have more of the saturated yellow color than the regular stamp.

One might argue that the light source in the scanner may not really simulate the actual viewing conditions. It is a valid criticism. Another is that I am averaging over the entire picture, and there are certainly more pronounced local variations. I do check to see if the color in the scanner is true using i1 software. And having scans of the 4 items under exactly similar conditions, while not ideal, at least presents a standard. Nonetheless, I don't think I'm learning too much from this exercise, other than to note that Red and Green do seem to vary on the low intensity end considerably among the 4 examples.

Trying something else, I now focus in on an area where I believe I do see a lot of variation, the hair and forehead.

first posted 4/1/2009