Today’s Question: Suppose I photograph a painting with the intent of making a print of it that is as faithful as possible to the original. Assuming I have a good, calibrated monitor and good printer with a good profile for the paper I use, can I get a good result if I simply place an 18% gray card in the camera view and use Photoshop to make it look like the original card?
Tim’s Quick Answer: This is actually a good example of a scenario where using a product such as the ColorChecker Passport (https://timgrey.me/colorchecker) from X-Rite to create a custom profile for your camera based on the conditions under which you are photographing the painting.
More Detail: While photographers generally want the colors in their photos to be “accurate”, we also want to exercise a bit of creative interpretation. So we might warm up an image more than the scene really appeared, or boost the saturation a little bit.
In some cases though, such as with product photography or when reproducing a painting or other artwork, you often want the colors in the final photo to be as close to a perfect reflection of the original as possible. In other words, you want to have a photo with accurate colors that appears as though the scene had been illuminated by perfectly white light (with no color cast).
In this type of situation there are a variety of approaches you could take to help ensure more accurate colors. As noted in the question, you could include a gray card in the frame and then adjust the colors so that gray card appears perfectly neutral gray.
You could also use a custom white balance setting in the camera, which is a somewhat automated approach to the use of a gray card for a post-processing adjustment. In effect, the gray card is neutralized in the camera rather than after the capture.
An even better option in terms of color accuracy is to use a product such as the ColorChecker Passport from X-Rite Photo (https://timgrey.me/colorchecker). The ColorChecker Passport includes a variety of color swatches (including gray) that you can photograph under the same lighting conditions as the subject you’ll photograph. You can then photograph the subject with the same camera settings.
After the photo shoot, you can use the photo of the ColorChecker Passport to build a custom profile for that specific photo shoot. The profile can then be applied to the photos, to help ensure the most accurate colors possible.
You can get more details about the ColorChecker Passport here: