Apple's Aperture software uses bright red to show me overexposed and/or over-saturated areas of an image. Were I to print the image, these might cause problems.
Digital photographers who spend too much time on the Internet become utterly paranoid about blown highlights. With the limited dynamic range of digital sensors, “blown highlights” are areas so overexposed that they contain no data at all, or colors so over-saturated they shift hues.
In high contrast scenes, most of us try to preserve highlights, because blown-out highlights with zero data present a printing problem: No ink in the blown out area. It makes inkjet prints look weird. That’s why most processing programs, such as PhotoShop or Aperture, allow you to see over-exposed areas of your images.
I rarely print my images. This contains overexposed and over-saturated areas, as shown above, but correcting them would make it a far less dynamic image.
Usually, I try to adjust images to preserve highlights, either through underexposure at the time of capture or through post-processing trickery. But not always. You see, very few of my images get printed. Mostly they are shared online, where they are backlit and vibrant and where bright highlights add to their punch.
If I used the exposure or recovery sliders to eliminate hot spots in this image, it would get greyer and flatter, and the girl in shadow would fade further. Yet in the final image below, I don't think the shoulders of the T-shirt destroy the image. Do you?
While post-processing rehearsal images from Dancing With The Ojai Stars, I intentionally blew out highlights and darkened shadows to raise the midtone brightness and boost contrast. It gives them a little more snap than you might normally get at high ISOs in a dance studio.
Perhaps the shoulders would ruin a print, but they look fine to me. The moral of the story? Use your camera and software highlight warnings judiciously, with knowledge of the image's end-use, and learn to trust your experience.
