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Battle Royale 2: Smartphones face off, screen to screen

How does Apple's Retina Display for the iPhone 4 compare with the HTC Evo 4G's screen?

Three phones step in, one survives... Eric Franklin/CNET

Editors' note: If you've already read "Battle Royale: Five smartphones face off," then you may experience some deja vu when reading this article. We've used the same tests and presented the article in the same style. Only the phones in question and the details of their performance have changed.

A few months ago in my never-ending pursuit of pain and sadness, I volunteered to test the display quality of five of the most popular smartphones at that time. Using DisplayMate Multimedia Edition for Mobile Displays, I put each phone through a battery of tests and lost a couple of weekends in the process.

With the recent release of the iPhone 4, as well as the hype that's been generated by the "Retina Display," now's the best time to determine just how good the display really is. I've decided to compare the iPhone 4's screen with only two others: the winner of the last roundup, the Motorola Droid, and relative newcomer the HTC Evo 4G. The Evo was chosen because of its popularity and relatively gigantic screen.

Like last time, we used three different types of tests to evaluate each phone:

Scientific measurements: We used the Konica Minolta CS-200 ChromaMeter to test the maximum brightness, black level, and contrast ratio of each phone and reported numbers for each of these three tests.

Test pattern screens: We used several DisplayMate Mobile test patterns to test for color-tracking errors, 24-bit color, and font legibility, among others.

Real-world: Finally, we conducted real-world anecdotal testing using 3D games, photos, and a little tool I like to call "the sun" to test the diffuse reflectance of each display.

All test screens were viewed within each phone's native gallery application. Some phones may handle pictures differently--and even improve them to some extent--outside the application. That said, we believe that testing within the respective gallery applications is still a viable test, as this is where most users will view pictures on their phones.

Note: Since we conducted our first round of tests, the Motorola Droid has received some noteworthy changes. When the Motorola Droid is upgraded to version 2.1, the Gallery (the principal image viewer for the phone) is downgraded to 16-bit color from its original full 24-bit color in version 2.0. Fortunately, version 2.1 of the Android Browser on the Droid still delivers full 24-bit color. Presumably these errors will be fixed in a future software upgrade, so the Droid will at some point return to its original, excellent 24-bit color. The tests here reflect the Droid in its 2.1 incarnation.

In order to diminish potential repetition, I'll dive right into the details of how each phone performed; if you'd like to know more about our tests, you can binge on nerdy details in our "How we tested" section at the bottom of this article. Please note that this is an evaluation of each phone's screen performance and nothing else. Check out the full reviews of these phones to determine which is right for you. Also, DisplayMate recently conducted a more technically focused evaluation of the Motorola Droid's screen that I recommend you check out.

The bottom line
Here's how we rank the phones in screen performance:

  1. Apple iPhone 4
  2. HTC Evo 4G
  3. Motorola Droid

Keep reading to find out why we ranked them this way.

I know everyone has strong opinions and usually fiery passions about their smartphone of choice, so I don't expect everyone to agree with my assessment or the methods used in drawing my conclusions. If there are any questions about how I came to my conclusions or anything relevant I may have left out, please leave a comment saying as much. Also, if you'd like to see even more detailed information of each phone's performance, let me know. If enough people are interested, I'll do a follow-up post with that information.

Lastly, though I hope consumers get something useful out of this, I'd also be happy if the manufacturers of the phones took a serious look at these results and at least considered them when making their respective hardware and software revisions. We all want these phones to continue improving, and I'm just attempting to contribute to the cause.

Apple iPhone 4
The iPhone 4 was the best performer of the three phones we tested. Although, its contrast ratio was not as high as the Droid's, the iPhone 4 was capable of displaying 24-bit color and was able to display colors in games and pictures with pop and life while still being accurate. The iPhone 4 won in most of our scientific tests and also had the best performance overall in our real-world tests. As it stands now the iPhone 4's is the best smartphone screen on the market.

HTC Evo 4G
In this round of three, the Evo 4G was a fairly close second to the iPhone 4, although it had the lowest brightness and contrast ratio of the three. The Evo 4G couldn't compete with the iPhone 4 in white-level saturation, or real-world color, but was able to display 24-bit color, unlike the Droid. Also, its extra-large screen is the best for viewing text.

Motorola Droid The Droid achieved an incredibly impressive contrast ratio, given that it's not OLED-based. However, whereas in our last roundup the Droid had the most-accurate colors of any of the phones, this time, the iPhone 4 is the winner in those categories.

How we tested
We measured each display's brightness, black level, and contrast ratio using the CS-200 and test patterns provided by DisplayMate. All phones were tested at their maximum brightness with full battery charges. All readings were conducted in a completely dark room.

Phone name Resolution Brightness Black level Contrast ratio
Apple iPhone 4 960x640 pixels
510.4 cd/M2 0.30 cd/m2 1664:1
Motorola Droid 480x854 pixels
410 cd/M2 0.17 cd/m2 2412:1
HTC Evo 4G 800x480 pixels
363.38 cd/M2 0.38 cd/m2 957:1

Test patterns: All test pattern tests were conducted in a completely dark room.

White-level saturation: This test includes a number of rectangular blocks on a bright, white background. Peak white is represented by the block labeled 255. The closer a screen gets to displaying 255, the more likely it'll be to show certain colors when viewing a really bright screen. The iPhone 4 had the best performance here, displaying up to level 254. The Droid followed with 252, and the HTC Evo 4G with 251.

Color scales: Tests the display's ability to show 25 distinct intensity levels for each of the 10 primary colors, from black to peak brightness. A perfect showing would have each color with 25 distinct steps. The iPhone 4 shows nearly 25 distinct steps, but its darkest step (not including black) cannot be seen. The HTC EVO 4G shows most of the 25 steps, but a couple near the light end of the scale are compressed. The Droid had the best showing, with no compression at the light or dark end.

Color tracking: This screen tests the LCD's capability to display the grayscale uniformly and accurately without any color tint problems. The iPhone 4 had the best presentation here with an accurate grayscale and no apparent color tint problems. The HTC Evo 4G revealed a slight bluish tint, and the Droid had an apparent green tint problem in several of the grayscale steps.

RGBW smooth color ramp: This an excellent test for determining whether the LCD can display 24-bit color. If the scale is smooth, without visible "steps," the display should be capable of 24-bit color. If not, it's likely limited to 16-bit, or possibly 18-bit, color. The iPhone 4 and the HTC Evo 4G were able to display 24-bit color. The Droid failed the 24-bit color test, as it wasn't able to show smooth scaling in its native Gallery app.

Fonts: We tested black, gray, and white fonts on different combinations of black, gray, and white backgrounds. Depending on how the phone handles things, certain combinations may affect the text's legibility. The phones had no problems when displaying text; however, with the iPhone 4's high resolution and relatively small screen, text--though sharp and crisp--was small and we had to strain our eyes to see it properly. The Droid's text was slightly larger and not as fine, but we felt the HTC Evo 4G, with its larger screen, had the best text-displaying capability.

Displaymate Mobile's white-level saturation test. DisplayMate

Real-world tests
Coca-Cola photo: A high-quality picture of a Coke can can be used to test how close the phone can come to reproducing colors from the real world. We used a real Coke can as reference. The iPhone 4 achieved the closest approximation of the can, with a nice, deep red and a metal top that looked appropriately more silver than gray. On the Evo 4G, the red looked washed out in comparison. The Droid's color isn't as deep as the iPhone 4's, nor as washed out as the Evo 4G's, but much of the perspiration detail seen on the iPhone 4 and Evo 4G can't be seen on the Droid.

Mars photo: We used a picture of a sunset on Mars to test the display's real-world false contouring threshold. The sky should appear to smoothly transition in color. If visible steps are noticeable, the phone has a false-contouring problem. Both the iPhone 4 and HTC Evo 4G had nearly perfect-looking skies, with the iPhone 4 looking just a little better. Though the Droid's sky looked great in our last roundup, now the sky's color transition isn't smooth at all, with very apparent color shifts and dithering. Downright ugly.

Game: We used Raging Thunder on the iPhone 4 and Raging Thunder Lite on the HTC Evo 4G and Motorola Droid to evaluate each phone's color performance in a fast-moving game. The HTC Evo 4G's colors looks slightly washed out, making the game seem a little drab. The yellow on the car we drove didn't have much pop to it and looked dull compared with the others. Also, text on the Evo 4G's screen looked slightly blurrier. The Droid's colors were slightly livelier. The iPhone 4 had the best game contrast ratio of the three, with deep and detailed blacks and bright light colors. The colors really pop, especially the green in the passing trees. Also, the shadows on the car were more defined and noticeable.

Diffuse reflectance: Some screens are more reflective than others, but what matters most is how reflective they are under extreme conditions; you don't get more extreme than a sunny day in San Francisco. In this round, all three phones performed at about the same level, with decent viewing from the optimal angle of straight on and lots of glare and reflectance when in direct sunlight. For the sake of your eyes, I don't recommend testing this without sunglasses on.

The Sun, from a Mars perspective. Each phone should display a smooth transition in intensity and color of the skyline. NASA