On Jan 8, 2009, at 1:57:32 PM, tlbepson wrote:
What is the relationship between the monitor profile and the LUT? Am I correct in thinking that the profile contains the instructions used by the Spyder software as to how the LUT is modified (in addition to the info used by the system's color management aware appss)?
___
Yes, the profile contains a special tag, where the LUT data is stored, to avoid issues where the profile gets seperated from the LUT corrections, which used to happen when they weren't stored together.
The reason I ask is that I'm considering starting from scratch with v3.0.7 because I'm finding it sort of odd that when I calibrate, my luminance level seems to be lower than it should be given that I'm using an LCD monitor (NEC 2090Uxi) and it's only about a year old--99-100 cd/m^2 for a target of 6500k/2.2.
___
Most year old LCDs are capable of more than 100 candelas (though I have a $7000 Eizo that can't make much more than 70 candelas...)
You don't make it clear if the raw luminance of the display is this low, with the backlight control all the way to max, or if thats the result after calibration, or if its after calibration, if you had a target value of 100 candelas built into your target, or not, so there are various possibilities here.
I think it should be much higher and I'm wondering if in the process of recalibration, the lum level is constantly being adjusted downward as the process is sort of iterative.
___
No, the process isn't iterative, but what the process is depends on the version of our software you are using, the settings you tell our software your display has, and the type of calibration you choose to do. If you do a visual calibration, then the display will not be dimmed, it will be run at whatever brightness is in place when calibrated. If you use a measured calibration, then it will be tuned to the brightness defined in the target. Other features could also have an effect. For instance, if you claim to have RGB Gains controls, and try to tune those to define the whitepoint, that can lower total luminance (and is not generally a good idea with LCDs anyways).
I was thinking that if I do not load the Spyder Utility on boot, that the LUT would not be modified
___
No real reason to do this manually this way, the tools you need are right in the software.
and I think the monitor profile would not be loaded--
___
Thats set at the OS level, so will continue to be used once its been loaded properly once, even if the Utility is not running...
not sure if I would also need to remove the profile in the Color Management tab in the Properties for the monitor--which would leave me with an UNprofiled (un-modified LUT) monitor.
___
It would leave you with a mess, I wouldn't suggest doing any of this. Since loading and unloading the LUTs on Windows requires a utility or application under Windows, its not a simple situation. But the solution is simple: Launch Spyder3Elite, go the the SpyderProof screen (you can go directly there from the Go menu, but if you've been mucking about with your profiles, it would make sense to build a new profile first) and then open the Colorimeter window. With the "before" setting selected, you can measure the screen without the LUTs in place (Null LUT data loaded), and with the "after" setting selected you can measure the screen with the LUTs in place. If they are lowering your white luminance, you can measure how much. You should expect them to be lowered some, if you have a whitepoint other than "native" targeted, as thats how non-native whitepoints are set: by lowering two of the three color channels until the correct balance is achieved. Targetted white luminance (if you have one set) will not be affected by the LUTs being on or off, however, as those are set with the screen's backlight control not in the LUTs.
I would then use the NEC OSM to reset various monitor settings--contrast, brightness, black level, RGB, etc.)...
___
Reset those to appropriate default values before calibrating, tell the software what controls you have (using the Edit Display wizard in the menu) before you begin, and then adjust any of these controls that the software tells you to use. Leave the rest untouched. That covers On Screen controls...
Once those steps were accomplished, I'd start the Spyder Utility and choose a "full calibration". What do you think?
Sounds like your the kind of guy that takes your lawnmower apart, and makes "improvements"... I'd suggest following the recommended process; this stuff is complex enough without inventing your own unique ways of doing it! There is nothing cumulative or sticky to worry about, if you redefine your Display characteristics (only necessary if they were wrong previously), and run a full calibration (available from the Go menu as well, in the latest 3.0.5 and higher versions), then everything is redone. If you choose to define a new target, then all the details of how your display will be calibrated are reset as well.
--
C. David TobieWW Product Technology Manager
Digital Imaging & Home Theater
Datacolor
CDTobie@...
www.datacolor.com/spyder3