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Relationship between monitor profile and LUT?

Relationship between monitor profile and LUT?

2009-01-08 by tlbepson

Hi David...got a couple of questions for you...

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)?

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. 

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. 

I was thinking that if I do not load the Spyder Utility on boot, that
the LUT would not be modified and I think the monitor profile would
not be loaded--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. I would
then use the NEC OSM to reset various monitor settings--contrast,
brightness, black level, RGB, etc.)...

Once those steps were accomplished, I'd start the Spyder Utility and
choose a "full calibration".

What do you think?

Thank you...

Terrie
http://tlbtlb.com/
tlbtlb@...

Re: [colorvision_group] Relationship between monitor profile and LUT?

2009-01-08 by cdtobie


On Jan 8, 2009, at 1:57:32 PM, tlbepson wrote:
Show quoted textHide quoted text
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 Tobie
WW Product Technology Manager
Digital Imaging & Home Theater
Datacolor
CDTobie@...
www.datacolor.com/spyder3

Re: Relationship between monitor profile and LUT?

2009-01-09 by tlbepson

>>cdtobie <CDTobie@...>: 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.

Good...I'm glad I'm understanding the concept...


>>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...)

Whoa!!! 


>>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.

Ahhh...sorry I wasn't clear. 

I am not adjusting the backlight--I don't think I have one actually.
Contrast is set to 62.2, Brightness is 100 and Black Level is 44.1--I
made these settings based on both the "boxes" ref'd in the
documentation and *my* real world view of diffierent live app
screens--web, Photoshop, Painter, ID, etc. 

I found the transition from CRT to LCD to be a bit jarring--as in
having difficulty reading the screen.

The candela reading is based on the final calibration reading from
within the v3.0.7 software--note I'm using a Spyder3Pro so I don't
believe I can set the value via target.


>>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.

OK...thank you for that clarification.


>>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.

I'm using visual--I don't think I can use Measured with the Spyder3Pro.


>>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).

This may be where I'm mucking things up.

When I installed v3.0.7 and began the calibration, using the NEC
2090Uxi OSM controls, I chose the RGB section and began to tweak the
RGB settings to adjust the RGB "bars" in the 3.0.7 software display
and it was weird because I wasn't really getting anywhere--none of the
"bars" appeared to adjust--even though to the best of my memory (and
notes), I was approaching the process in the same way I had in v3.0.4.
Note that in the NEC OSM display for the RGB section, I had chosen,
"Option 1" preset which at that point, showed 6500K as the Temp and
then there were suboptions that allowed me to adjust the following: R,
G, B and C, M and Y (I didn't mod the CMY values).

When I didn't seem to be getting anywhere, I went to the NEC
documentation and discovered that within the NEC RGB options, there is
a subset of options which allow you to adjust the HUE, SATURATION,
OFFSET and WHITE and I had been adjusting the HUE values/settings.

At that point, it seemed to me that what I should be adjust were the
WHITE values/settings (only R, G and B setting are available) so
that's what I've been doing and the TEMP is now shown as "CUSTOM" in
the NEC OSM, RGB section.

I don't know if I am correct in doing the calibration this way and I'm
wondering if what I've done is to mod the monitor's native white point
which I know is not advised for LCDs. 


>>No real reason to do this manually this way, the tools you need are
right in the software.

Ok...not sure how/what options (?) to turn on/off


>>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...

Yes! I understand that and what I'm looking to do is to NOT set the
LUT so that the monitor is in a "virgin" state--so to speak...

BUT...given what you are saying below...


>>But the solution is simple: Launch Spyder3Elite

Sticky wicket here as I'm using Spyder3PRO...


>>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) 

My current profile was done via the "full calibration" option via
Spyder3Pro yesterday (Wednesday 1/7/08)...


>>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. 

Soo...the "before" screen is WITHOUT the LUTs set rather than with
(what will become) the previous profile--assuming one calibrates again
and saves a new profile?


>>as thats how non-native whitepoints are set: by lowering two of the
three color channels until the correct balance is achieved. 

Yes...I understand that now and I think what I've done is incorrect
because changing the native whitepoint of an LCD is not recommended?


>>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.

Ok...


>>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...

Ok...I think I have done that but I will try this again just in case
because I've been playing with this over a period of days and who know
what I've mucked up in the process...'-}}


>> Once those steps were accomplished, I'd start the Spyder Utility and
choose a "full calibration".

Got it...


>>I'd suggest following the recommended process

I do think that, at least initially, I followed the recommended
process but it was when I ran into the "problem" (maybe it wasn't a
problem) with mod'ing the HUE settings and then starting again by
mod'ing the WHITE settings that I got somewhat concerned about what
was being generated. 


>>There is nothing cumulative or sticky to worry about, 

This is the key for me because I thought the process was
cumulative/sticky which is why I thought that starting all over again
would be the best thing to do but from what you are saying, I don't
need to do that...


>>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.

Ok!

Thank you!!!

Terrie
http://tlbtlb.com/
tlbtlb@...

Re: [colorvision_group] Re: Relationship between monitor profile and LUT?

2009-01-09 by cdtobie


On Jan 8, 2009, at 7:43:31 PM, tlbepson wrote:
Show quoted textHide quoted text
The candela reading is based on the final calibration reading from
within the v3.0.7 software--note I'm using a Spyder3Pro so I don't
believe I can set the value via target.
---
Right, in Pro, the only way to get luminance control is to choose the Ambient Light option, and make sure your room light is at a level that will trigger the desired matching screen brightness. This then will put up a screen which includes a bar with an marker that you are supposed to adjust until your screen brightness is in between the tick marks on the bar. No numbers involved, as there are in Elite, just a target zone. As long as you don't choose Ambient Light mode, you'll be in Visual Mode, and whatever backlight level you've set will be used. You do have a backlight control, but it may be called "brightness" in your On Screen Controls...
--
C. David Tobie
WW Product Technology Manager
Digital Imaging & Home Theater
Datacolor
CDTobie@...
www.datacolor.com/spyder3

Re: Relationship between monitor profile and LUT?

2009-01-09 by tlbepson

>>cdtobie <CDTobie@...>: Right, in Pro, the only way to get luminance
control is to choose the Ambient Light option, and make sure your room
light is at a level that will trigger the desired matching screen
brightness. This then will put up a screen which includes a bar with
an marker that you are supposed to adjust until your screen brightness
is in between the tick marks on the bar.

Well cool! I didn't know that as I've never chosen the Ambient Light
option...I'll give that a go...

One last thing. I am no longer getting the "this is your new profile
name" screen. I submitted a support ticket on it and was told that I
should see it if I choose to do a "full cabliration". I replied that I
*had* chosen the "full calibration" option and did not see profile
name screen so I was not able to use my own choice of profile name
which is what I prefer to do. I've not heard back from support
yet--this was 2 days ago. 

I had not changed any of the Spyder3Pro Utility options so I'm not
sure why I am not seeing that "profile name" screen. The profile name
is now defaulting to "spyder3pro.icm" and the file date/time stamp
does change to reflect new the "full calibration" process. 

My guess is that support passes this sort of info on to the software
side but just in case, I thought I'd let you know.

Thank you!

Terrie
http://tlbltlb.com/
tlbtlb@...

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