There's been a ton of controversy over this single online image. The Dress. Saying that this has “gone viral” would be a gross understatement. This image confused people to the point of establishing solid factions: is the dress gold and white or is it blue and black?

I've been a hobby photographer for about 30 years. This should be an exercise for photography students. I would focus on the background, seen on the right side of the image. It's way over-exposed even when you balance the dress color for blue-black. Adjusting for that over-exposure makes the dress even darker, and further away from white-gold. One way to tell the image is over-exposed is to look at bright areas. There's no detail and they bleed into dark areas (creating a halo effect).

Most people take pictures using automatic or “full-program” settings, especially with the advent of smart-phone cameras. The camera adjusts for various lighting conditions based on presets stored in memory. It will measure average light hitting the sensor and adjust color balance and exposure based on a selected preset.

Strong back-lighting, shown in this image, will cause even the best digital sensors to misinterpret the image. The exposure will be off, since automatic settings take an average and adjust settings based on that average. Strong lighting offsets the average.

To further complicate things, different lighting (indoors, outdoors, sunny, cloudy, fluorescent, etc.) changes color balance. Our eyes automatically adjust, and do so very quickly, so we don't notice the difference. Digital image sensors, and film for that matter, respond differently to different types of light. It's difficult to determine lighting conditions simply by looking at the image.

Interestingly, just inverting the image causes the dress to switch from gold-white to blue-black. This makes perfect sense because these are opposite colors in photography. Again, there's not enough of the background to determine if inversion is correct.

Some report it's an optical illusion. Some see a gold-white dress and others see a blue-black dress, even when looking at the original, unprocessed image. Wired reported a quote from neuroscientist Bevil Conway, citing the way our eyes discount some colors. “So people either discount the blue side, in which case they end up seeing white and gold, or discount the gold side, in which case they end up with blue and black.”

Since we don't know original lighting, exposure information, or how much post-processing was done, the dress can be any color your mind wants it to be.