The iPhone 5 Display: Thoroughly Analyzed

I enjoyed it. Not out of any interest in the iPhone 5. But as a (somewhat) technical article about how displays are measured.

One of the more interesting articles of the day imo.

What is the real-life difference between saturation cranked up via software compared to a screen with inherent high saturation?

Cranking up saturation in software is likely to introduce artifacts due to the precision of the data being sent to the panel. For example, most framebuffers are still at most represented with 24 (color) bits per pixel, and the signals being sent from the GPU to the display may not have much more precision than that either (how much precision they have can depend on a variety of factors). The immediate consequences of this:

User-mode software is unlikely to be able to increase saturation without hardware assistance, because it ultimately has to send 24bpp pixel data to the GPU. The dynamic range possible in 24bpp is pretty limited when you factor in what happens to it after it goes through the rest of the pipeline.

Kernel-mode code, drivers, and firmware on a GPU can potentially adjust saturation more accurately by sending higher-precision color values out to the display, if it supports it. Not many displays today support higher than 24bpp precision, but such displays do exist. Unfortunately, the inputs from user-mode software were 24bpp, so some accuracy has already been lost and any lost accuracy will be compounded by saturation changes produced at this level.

Finally, the display itself may actually be reducing the quality of input signals - many panels have less than 8 bits per channel (24bpp = 3 channels) of precision and represent higher accuracy signals with dithering and other techniques. This can make the result of adjusting saturation in software even worse.

So, in practice, adjusting saturation in software will produce visible artifacts for images that need high dynamic range or high precision.

I believe you are right that contrast is more important than both gamut and color accuracy, but a higher gamut will make images feel more alive and give them more "pop", especially in the reds and yellows (as the article discusses).

A high contrast ratio helps prevent banding artifacts in dark shades of gray.

A high gamut does the same for color.

With a high contrast display with a low gamut (a display that can't output a very wide range of colors) you might see banding in reds or yellows even. The brain will compensate for lower gamuts but the image will look more washed out. As an example, a color photo in on newspaper is clearly less vibrant than the same image in a glossy magazine or online.

Also, color accuracy and gamut are not necessarily the same thing. The typical human eye can see far wider range of colors - a wider gamut - than is possible in any display or print technology. Displays are a compromise. sRGB is far less than the human eye can see, which is why image editors use the wider ProPhoto RGB or Adobe RGB gamut (color spaces) and then after editing cleverly compress down to sRGB (or for particular applications, the exact color space of a particular printer / paper combination or of a particular display).

Low-gamut means some colors are missing and compressed to colors that can be shown - so the richest red becomes an orangish-red. While inaccurate, this isn't quite the same the same thing color-shifting all colors in an image, such as the yellow-cast you might see with indoor lighting, or blue-cast with outdoor shadows. All displays introduce color-shifting inaccuracies as well. High-gamut displays have a wider color pallet and are generally tuned better at the factory.

I expect high-gamut displays will just "feel" better in the same way retina / high-res displays do.

[edited for clarity]

Jl