A spec that is often touted, but rarely informative when it comes to screens, is the contrast ratio. This is essentially a comparison between the brightest and darkest image a screen can produce. you might think this would do a good job telling you which screens have the inky blacks and crisp whites you like to see, but DisplayMate’s Raymond Soneira has published some real world testing on a number of smartphone screens that says otherwise.
Manufacturers tend to measure contrast ratios in completely dark rooms with all white and all black images. This is fine for PR spin, but in real life, users won’t be in pitch black rooms with monochrome images. Soneira used four phones that represent a wide array of screen technologies; the iPhone 4, Droid X, Galaxy S, and HTC Desire. Using an Integrated Hemisphere light source, Soneira was able to perfectly simulate light conditions from pitch black, all the way up to 40,000 lux, or roughly equivalent to indirect outdoor sunlight.
Soneira observed the true contrast ratios, and how they were affected by screen reflectivity as the brightness ramped up. as you can probably guess, the published contrast ratios didn’t quite match up with real world performance.
On the top of the heap were the iPhone 4 and Samsung Galaxy S. the iPhone uses an IPS LCD screen, and it was helped by having an extremely high maximum brightness. as the light picked up, it was able to remain more usable. the Galaxy S edged the iPhone out slightly with its Super AMOLED Plus screen. while it did wash out, Samsung’s low-reflectivity combined with high maximum brightness made it more usable in bright light.
The HTC Desire uses a traditional AMOLED screen, and it was the worst of the tested screens, despite having very high advertised contrast ratios. the screen was so reflective that any benefits from AMOLED technology was lost in even moderately bright light. the Droid X with its middle-of-the-road LCD also didn’t fare particularly well, but better than the Desire. the Droid X screen washed out and produced some noticeable banding.
The takeaway from this study is that the numbers advertised by OEMs might have little bearing on your real world experience. after all, you probably don’t spend a lot of time in perfectly dark rooms.