Hi,

I began to calibrate my 42LG50 with my i1 display LT and ColorHCFR. I have a PS3 and I use AVS HD 709 v.1.2.

I wanted to do some tests before doing the full 10-points IRE and CMS calibration, by adjusting only the contrast and the brightness to assess the gamma curve. The default expert mode was giving me a gamma curve too low (1.8), with a high gamma drop in the range 60% to 100% gray (too much contrast). I then adjusted the contrast down and the brightness accordingly. This gave me a nice gamma curve near 2.22 and a light ouput of 35 ftl at 100% gray.

The problem is : I exited my calibration DVD and then played it again and I did a grayscale reading again with ColorHCFR. With the same settings, everything was messed up :confused:

The gamma curve was not what I had obtained before and was worse that what gave me the default expert mode. The gamma curve was then at 1.6. Also, the light output a 100% gray was then at 29 ftl :eek: Also, I found out that when adjusting contrast and then selecting 10-points IRE method instead of the 2-points method, light ouput changed a bit, which is not normal. It seems like the TV was reajusting something, maybe the EyeCare option (even if it is not explicitely present in expert mode) or wathever setting that messed up the gamma in the range 60% to 100%.

I did some test with the cinema mode and there were no problems like the ones I experienced with expert mode.

Could this be a memory bank problem?

Can someone help me? Have you experienced the same problem with inconsistent TV settings?

My guess would be that a room light sensor is on. Not only can the ambient light in the room change things, but also sometimes even the brightness from the test pattern itself can cause the TV to change light output and gamma.

My guess would be that a room light sensor is on. Not only can the ambient light in the room change things, but also sometimes even the brightness from the test pattern itself can cause the TV to change light output and gamma.

That was my hunch. The 42LG50 has an "Intelligent Sensor" picture mode that do that, but it should be off in the 2 picture experts mode. Also, I disabled "Fresh Contrast" which is a dynamic contrast option.

Maybe it is a firmware bug? What should I do? Should I enter service menu to see what's going on or return the TV?

The experts mode are the only ones that have the CMS and a 10-points IRE calibration settings.

That was my hunch. The 42LG50 has an "Intelligent Sensor" picture mode that do that, but it should be off in the 2 picture experts mode. Also, I disabled "Fresh Contrast" which is a dynamic contrast option.

Maybe it is a firmware bug? What should I do? Should I enter service menu to see what's going on or return the TV?

The experts mode are the only ones that have the CMS and a 10-points IRE calibration settings.
Well, I remember on the last couple of LG plasmas I did, I found the expert mode to be unuseable because of very poor gamma. It's been a while, probably a year, and of course they were plasmas rather than an LCD like yours. I doubt you'd be able to find anything in the SM that would help, but if someone with experience on your model knows of something feel free to correct me.
My personal experience with LG has not been good. That's not to say I would never consider owning one if they make improvements; it's just that the LG products I've calibrated have had puzzling inaccuracies. Calibration still made a big improvement, though.

One more thing you might try is letting the pattern stabilize on the screen for about 5-7 seconds before taking the reading. I would not get my hopes up, though.

I found out what was the problem.

Well, it is not really a problem or a bug with the TV, but rather a really poor implementation of the 10-points IRE calibration controls of the experts mode.

In short, in the experts mode, brightness and contrast must be set IRE point by IRE point (10 in total) by adjusting their green balance and then adjusting the red and blue balances accordingly to have the right gamma curve. Adjusting the overall contrast or brightness controls messes up things and enters in conflict with the individual IRE controls.

For example, if I adjust brightness and contrast with the global controls and do a reading with my Display LT, things will be fine at first, because the default values (0) of the IRE controls seems to move accordingly with them.

Then if I turn off the TV and turn it on again and do the readings again, I will not have the same results because the TV reverts back the default (0) IRE controls to their original values (that is, without the previous effect of the overall brightness and contrast adjustment).

I did test and I don't have these problems when I only adjust these settings :
-Backlight
-Sharpness
-Gamma
-Color
-Tint

I did another test where I decreased the green balance of the 100 IRE control, to decrease the contrast at 100% gray, and there was no difference in readings before and after turning on and off the TV. If then I decreased the global brightness or contrast control, things were messing up again.

So, calibration will be very very long as I will have to adjust the contrast/brightness for each IRE point to have in the end the right gamma curve and also to have the right chromatic coordinates (0.313/0.329) :(

I found out what was the problem.

Well, it is not really a problem or a bug with the TV, but rather a really poor implementation of the 10-points IRE calibration controls of the experts mode.

In short, in the experts mode, brightness and contrast must be set IRE point by IRE point (10 in total) by adjusting their green balance and then adjusting the red and blue balances accordingly to have the right gamma curve. Adjusting the overall contrast or brightness controls messes up things and enters in conflict with the individual IRE controls.

For example, if I adjust brightness and contrast with the global controls and do a reading with my Display LT, things will be fine at first, because the default values (0) of the IRE controls seems to move accordingly with them.

Then if I turn off the TV and turn it on again and do the readings again, I will not have the same results because the TV reverts back the default (0) IRE controls to their original values (that is, without the previous effect of the overall brightness and contrast adjustment).

I did test and I don't have these problems when I only adjust these settings :
-Backlight
-Sharpness
-Gamma
-Color
-Tint

I did another test where I decreased the green balance of the 100 IRE control, to decrease the contrast at 100% gray, and there was no difference in readings before and after turning on and off the TV. If then I decreased the global brightness or contrast control, things were messing up again.

So, calibration will be very very long as I will have to adjust the contrast/brightness for each IRE point to have in the end the right gamma curve and also to have the right chromatic coordinates (0.313/0.329) :(

My first impression after reading your OP (and prior to the rest of the responses) was are you sure you are saving the settings? Your later post about them changing once power is turned off and on makes me question this even more.

My first impression after reading your OP (and prior to the rest of the responses) was are you sure you are saving the settings? Your later post about them changing once power is turned off and on makes me question this even more.

Yes the settings are saved (if I set contrast to 80 and then come back it is still at 80). The problem also happens when I change the picture mode and then return to the expert picture mode, without turning off the TV or by exiting the calibration DVD and then re-enter it.

There is no problem when adjusting other picture modes like cinema, standard, etc. Maybe because these modes does not have a CMS and a 10-points IRE calibration option.

Then if I turn off the TV and turn it on again and do the readings again, I will not have the same results because the TV reverts back the default (0) IRE controls to their original values (that is, without the previous effect of the overall brightness and contrast adjustment).

I think I would classify this as a bug :) Given this limitation, what I would do then is leave brightness/contrast alone in the main menu and use the 100% expert controls to target your 100% luminance by raising/lowering red, green and blue in tandem. I'd then do that same operation for each of the other points until the luminance get you close to your target gamma. I'd then go back and tweak each point to get the proper color balance - knowing that this will have some affect on the luminance. It'll be an iterative process and you'll most likely have to compromise a bit on the gamma/luminance in order to get the proper color balance.

hope this helps,


--tom

I was working with my brand spanking new i1 today and also discovered that settings change... as the tv warmed up or as the i1 warmed up with the tv, don't know which one. It actually takes several minutes for everything to settle down (changing by 1 cd/m^2 per minute), and half an hour or more for everything to really settle down (not changing by 1 cd/m^2 even over several minutes).

I was working with my brand spanking new i1 today and also discovered that settings change... as the tv warmed up or as the i1 warmed up with the tv, don't know which one. It actually takes several minutes for everything to settle down (changing by 1 cd/m^2 per minute), and half an hour or more for everything to really settle down (not changing by 1 cd/m^2 even over several minutes).

Specific behavior will depend on the display type but typically I wait at least 30 minutes or so before taking any measurements in order to let the display warm up. I know my older CRTs are shifted toward red in the grayscale when turned on "cold" and I know that our main LCD is dimmer for the first 15-20 minutes until it finally stabilizes.

cheers,


--tom