Re: Setting up HP DreamColor LP2480zx monitor for work in Color

Hello,

I work for HP, focussing on the HP DreamColor LP2480zx display. I will be happy to help you to understand how to get the best out of this product.

The HP LP2480zx is intended to be a CRT-replacement display, and is already being sold into animation, television, film, photography and print applications. The industry is well aware of the need for an LCD solution that can replace CRTs. The HP LP2480zx is an affordable candidate for this transition, and many users are finding that they like what they see and can trust the display.

The LP2480zx is designed to provide highly accurate color AND gamma conformance with whichever standard color space is selected by the user. For example, if the user selects "Rec. 709", then the monitor will behave as a completely accurate Rec. 709 device. The parameters for this compliance are:

* Chromaticity of the red, green and blue primaries (the gamut)
* Chromaticity of the whitepoint (red, green, blue all maximum)
* Tone response (gamma)

Accurate compliance with gamut is achieved by four things:

* A super-wide native (physical) gamut in the display, which completely encloses the gamuts of Rec. 709, Adobe RGB and others, and almost completely encloses (97%) the very wide gamut of DCI-P3 (try doing THAT with a CRT!!!);

* Accurate calibration (for every unit) in the factory (or by the user, using the HP Advanced Profiling Solution for the DreamColor Display);

* High-precision color and tone mapping with the 36-bit HP DreamColor Engine (an electronic subsystem in the monitor); and

* A true 30-bit panel (despite rumors to the contrary!) which allows the HP DreamColor Engine to map input colors to a true palette of 1.07 billion physically displayable colors. This reduces color error when performing the color and tone mapping.

Accurate tone response (gamma) is achieved through the same path, and is enabled by the panel's 1000:1 contrast ratio.

(Note: the HP LP2480zx does not implement any "dynamic contrast ratio" techniques, as HP regards these as inappropriate for a reference display.)

(Also note: some standard color spaces, such as sRGB, use a complex tone response curve consisting of a linear section at near-blacks followed by a gamma curve. The HP LP2480zx implements this type of tone response accurately for sRGB.)

Now, a question I have is, "what is the color space of the RED images?". If it's a standard color space, such as Rec. 709, then simply displaying the images on the monitor, with the monitor set to "Rec. 709" mode (using the on-screen menu) will give accurate results, as long as there's no color management being performed by the viewer application and/or the operating system.

Having said that, probably the best way to use the display is in "Full" mode, which means that the display's wide physical gamut is available to the computer. Of course, to achieve this, the Mac Pro must know the gamut, whitepoint and gamma of the LP2480zx's "Full" mode. On Mac OS X, this is usually achieved when the graphics card reads the display's "EDID" (Extended Device ID), which is a string of bytes in the display, which report such things as the manufacturer ID, the model number, the date manufactured, the physical size, preferred resolutions, etc, etc. Among those data is information on the display's color space (R, G, B, W and gamma). As long as the display reports these parameters correctly, Mac OS X can apply color management, "knowing" the color parameters of the output device (the display). In my view, this is the best way to go. Or, if you want a Rec. 709 workflow, then you can experiment with the display in "Rec. 709" mode.

"Full" is definitely the appropriate choice if the RED images are encoded for a wide color gamut. In this case, the viewer application will have to perform the necessary color management which accounts for the source profile. Then, Mac OS X can use the LP2480zx's EDID to account for the output device profile, and the color transformations should be accurate and trustable. Just like any color-critical workflow, it's up to the user to ensure that the chain of color transformations (if any) is correct. The LP2480zx provides both wide gamut and accurate color space compliance, depending on how you want to stack your profiles.

One word of warning, though: By default, the display's EDID doesn't get updated when you change the color space mode of the display. The recipe at the end of this message shows you how to enable "Auto EDID Update" so that Mac OS X will be notified that you changed the preset, and will therefore re-read the EDID. Note that when this happens, the desktop will blank for moment while Mac OS X responds to what is effectively a hot-plug event.

I hope this helps!

Best regards,
Dan Bennett

HP DreamColor Technologist


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Recipe for enabling Auto EDID Update (especially important for Mac users):

The as-shipped On Screen Display (OSD) settings of the LP2480zx will cause the Full gamut of the display to be reported whenever the EDID information is queried by the host computer even if a different color space preset is active. To enable the LP2480zx to report the active color space settings and immediately notify the host computer of the change, the Auto EDID Update setting (set to OFF in the factory) needs to be set to ON.

Mac users are especially encouraged to enable Auto EDID Update. When a monitor is connected to a Mac, the OS immediately reads the EDID and creates a color profile that reflects the color settings of the monitor. Since the LP2480zx can take on different color characteristics, if the user chooses anything other than the Full color space preset, if this change is not made, the Mac will install a color space profile that doesn’t match the current monitor settings. For example, if the user selects the sRGB color space preset, the applications that support color management will display very subdued colors.

The following steps will cause the monitor’s EDID information to be updated whenever a color space is changed, and will cause the Host to be notified by signaling Hot Plug Detection.

* Open the OSD
- Press any of the bezel buttons once
- Press the “Open OSD” button

* Open the Management screen
- The OSD opens on the “Main Menu”
- Press the “Next” bezel button until the “Management…” selection is highlighted
- Press the “Select/Open” button to enter the “Management” Menu

* Open the Auto EDID Update screen
- Press the “Next” bezel button until the “Auto EDID Update” selection is highlighted
- Press the “Select/Open” button to enter the “Auto EDID Update” Menu

* Change the “Auto EDID Update” setting to “ON”
- Press the “Reduce Set” bezel button until the “On” selection is highlighted
- Press the “Select/Save” button
- Press the “Select/Open” button to action “Save and Return”

* Exit the OSD
- Press the “Exit OSD” bezel button

Note: The Hot Plug Detect Support must be Enabled for the monitor to immediately notify the host computer of the color space change. If Hot Plug Detect Support is Disabled, the host computer will not learn of the color space change until the next time it happens to request the EDID information. On a PC, that may not happen until the cable is disconnected and reconnected. On a Mac, the next time the system reboots or resumes from sleep it will re-read the EDID and install an appropriate color profile.

Hot Plug Detect Support

Some older video cards and drivers may not respond correctly to the Hot Plug Detect events sent by the LP2480zx. If the user experiences issues at startup (or resume from sleep) where the LP2480zx is either blank or attempts to display the screen briefly and then goes blank repeatedly, the user should Disable the Hot Plug Detect Support.

To access the “Hot Plug Detect Support”.

* Open the “Video Input Control” menu
- Press any of the bezel buttons once
- Press the “Input Select” button

* Open the “Hot Plug Detect Support” screen
- Press the “Next” bezel button to highlight the “Hot Plug Detect Support” selection
- Press the “Select/Open” button to enter the “Hot Plug Detect Support” Menu

* Change the “Hot Plug Detect Support” setting
- Press the “Reduce Set” bezel button until the “Disable” selection is highlighted
- Press the “Select/Save” button to accept the highlighted choice

*Exit the OSD
- Press the “Exit OSD” bezel button