Tuesday, November 17, 2009

Color Accurate Monitors for Digital Artists

Problem: you are James Cameron working on an HD trailer of Avatar; you need to be 200% confident in the picture and color quality before posting it online: it's got to be just spectacular to uphold the Titanic reputation of Mr. Cameron. What monitor(s) do you need to use to be absolutely sure the picture is color accurate?

If you find out - let me know. Given the $230m budget of Avatar, it's probably the very best of the top-shelf equipment, with some stuff custom-developed specifically for the movie, along with special equipment to verify that the picture quality is adequate. $20K for a set would not be outlandish.

For the rest of us - photographers, videographers, digital artists on a budget: what display monitors would do a good job ensuring that we don't miss a bad spot, a discoloration or an artifact? Photographers and Red camera users working with raw 10-, 12- and 14-bit images rather than 8-bit JPEGs and MPEGs, the issue is rather huge: the banding artifacts we are seeing on a computer monitor - are they just on the monitor, or in the actual file? How can I be sure before sending them to the publisher? The only way to get a better idea is to get a monitor that is capable of bit depth higher than 8. Enter IPS panels and 30-bit (3x 10-bit) displays such as HP DreamColor LP2480zx and Dell U2410.

Being a complete noob with respect to critical color applications and color calibration, I set out to do what I do best: go through specifications and manuals, google around and try to figure out the differences between two popular displays that both claim fantastic color accuracy. Do not expect a lot of depth from this article (but do expect a little): it's merely an attempt to figure out the basics based on a 45-minute research. It did turn out to be a 6-hour research - but nobody's perfect.

We'll skip highly specialized - and expensive - color-accurate displays from Eizo and Lacie, and focus on two top models from HP and Dell. Both are 24-inch IPS (In-Plane Switching) LCD monitors with 1920x1200 maximum resolution and a host of usual inputs such as DisplayPort, DVI, HDMI, component and composite video. One is listed at almost $3K (street prices around $2,000), the other one - $600. Which one should I get?

Dell UltraSharp U2410 24-inch Monitor, $599 SRP
- 1920x1200 resolution
- IPS panel type
- Contrast ratio: 1000:1 (typ), 80,000:1 (Max, Dynamic Contrast on)
- 400 cd/m2 typical brightness
- 6ms Typical Response Time (gray to gray)
- 178/178º Max Viewing Angle (vertical/horizontal)
- 1.07 billion colors
- 110% (CIE 1976) Color Gamut
- 12-bit Internal Processing
- AdobeRGB - 96% Coverage
- sRGB emulates 72% of NTSC Color (100% Coverage)
- xvYCC Compatibility
- DVI-D, DisplayPort(DP), HDMI, VGA, Component, Composite inputs included

Pros: value. IPS-type monitors display a much wider color range than the prevalent TN-type ones, yet have lower brightness and contrast, and cost more. At $599 SRP, Dell U2410 is a great value with decent brightness and contrast on a par with the best monitors from other manufacturers.

  • Unlike HP LP2480zx, U2410 is not a 30-bit (10 bits per color component) monitor, according to UK reviewer TFT Central. Sadly, Dell misleads in its specifications by saying that the display is capable of over a billion colors. Dell conveniently forgets to mention that these colors are not all available at the same time. Only 16.7 million colors can displayed at any given time, a feature of most 24-bit displays (8 bits per color component).
  • Dell calibrates this monitor at the factory but does not offer any other means to color-calibrate it. Certainly, there are 3rd party color-calibration tools you can use for this monitor, but unlike HP, Dell not only does not offer any of them, it does not mention even a possibility of it.
  • Dell also engages in the usual and often misleading specifications game listing only the most advantageous items: the dynamic contract ratio of 80K:1 is utterly useless while a typical one of 1,000:1 can only be found in the manual.
  • Same goes for 6ms response time that only applies to gray-to-gray transition while the more realistic full black-to-white-to-black number is not listed at all. HP lists all these numbers up front as if saying, we've got nothing to hide.

Verdict: Dell U2410 is a great quality IPS monitor with 24-bit color. It is not however a professional tool for color-critical applications, and is comparable to HP LP2475w rather than DreamColor LP2480zx.

HP DreamColor LP2480zx Professional Display, $2,899 SRP
(in green are the specifications where HP either trumps Dell, or that Dell does not list)
- 1920x1200 resolution
- IPS panel type
- 1,000:1 Typical Contrast Ratio
- 250 cd/m2 typical brightness (maximum white luminance)
- 6ms Typical Response Time (gray to gray), 12 ms (rise+fall, full black-to-white-to-black)
- 178/178º Viewing Angle (vertical/horizontal)
- Over 1 billion colors in native mode
- Backlight Life (to half brightness): 50K hours
- Backlight Type: RGB LEDs
- Gamma/Tone Response: Programmable from "gamma" value of 1.0 to 3.0.
- Color Gamut: Native gamut approx. 133% NTSC (in CIE 1976 u'v' space)
- Adobe RGB Coverage: 100%
- sRGB Coverage: 100%
- Lookup Table: 12 bits per entry, 1024 entries per table
- Internal Processing: Min. 10 bits/color throughout video processing pipeline.
- Color Space Presets: 7 color space presets; 1 user-programmable plus six factory programmed: sRGB, Rec. 709, Rec. 601, Adobe® RGB, DCI-P3 emulation (97%), full gamut

  • HP LP2480zx specs show better color gamut (133% vs. 110% NTSC) and Adobe RGB coverage (100% vs. 96%), as well more presets and full programmability of its LUTs (Look-Up Tables) - essential for professional color applications. I'd venture that the better gamut and coverage do matter for very critical color grading applications.
  • HP offers HP DreamColor Advanced Profiling Solution for $349 on its web site, to calibrate the monitor, validate and trend its performance. No such thing at dell.com.
  • HP published a "mini white paper" about LP2480zx, "Understanding the HP DreamColor LP2480zx Professional Display’s 30-bit panel" where it explains what a 30-bit color is, and why it is better than 24- or even 18-bit color of mainstream monitor. Dell's mentions 1 billion colors on U2410, which is directly related to a 30-bit color (30 bits represent a number of a little over a billion), however UK's TFT Central in its U2410 review says that the screen "utilises an 8-bit H-IPS panel, capable of producing 16.7 million colours".
  • HP describes the 30-bit workflow and how to ensure that your computer configuration is fully 30-bit, from your application through the graphics card and its driver, to the cable (gotta use DisplayPort 1.1 or HDMI 1.3 for 30-bit - standard DVI is limited to 24-bit), to the monitor.
  • According to HP, they developed the LP2480zx in "close collaboration with DreamWorks Animation", for their color-critical applications. See PDF brochure on HP website.
  • HP "DreamColor and HP DreamColor LP2480zx Professional Display - Frequently Asked Questions" talks about various color spaces and the monitor's compatibility with them, the importance of low black levels, dimmability and tone response and its ability to synchronize to standard video frame rates.
Cons: lower brightness of 250 vs. 400 cd/m2; price.

Verdict: if you are James Cameron checking out biolumenance scenes of the Avatar HD trailer, you certainly need HP DreamColor LP2480zx, at the very least. In other words, if you utilize professional color grading applications requiring 100% color accuracy, this monitor fits the bill.

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