Hi all,

Sorry if the answers to some of these issues have been discussed to death - did try searching the forums first.

I've been looking into calibrating my UK model Sony 40W4000 LCD set for a while, and now have an Eye-One and the free HCFR software. I'm using some HD patterns via a disc in my PS3, and I'm referring to the GREYSCALE & COLOUR CALIBRATION FOR DUMMIES thread on curtpalme.com.

The TV doesn't have the conventional RGB LowEnd/HighEnd options. Instead it relies on a 5 separate ‘levels’ system, starting at Level 0 (dark) and ending with Level 4 (light). At each Level you can adjust R, G + B to a number between 0-1023 in order to get an accurate greyscale. Additionally, the set has no separate gamma controls, so I've been adjusting the 5 levels in order to also try and bring gamma into some sort of line (whilst still keeping the greyscale intact) – whilst it’s tough, this seems to work in principle. Sadly, the TV has no form of Colour Management System, so I'm stuck with what I'm given. Thankfully the primaries are really good (apart from blue).

Anyhow, my questions:

1) There seems to be some different opinions on whether you should a) use the suction cups to stick the Eye-One to the LCD screen or b) not - instead trying to get the sensor to 'lie' on the screen with the LCD at about a 30 degree angle.

Any advice? If I use the suction cups the screen does lighten at the points where the Eye-One sticks to the screen. However, I think the bit of the screen the sensor reads from isn't affected (i.e. lightened), but I'm worried this may be throwing my measurements off slightly.

2) Potentially silly question here:
Am I right in thinking that the conventional ‘brightness’ setting effectively raises (or lowers) gamma uniformly across the entire IRE range (and does nothing else)?

My current plan is to try and get my gamma line how I want it in terms of shape (which will be significantly too bright), and then uniformly darken the picture with brightness in order to get to a decent (darker) gamma. Seems easier to do it this way, as darkening the picture sufficiently via the Levels 0-4 system I mentioned earlier seems to cause problems (gamma line becomes VERY curvy).

3) Any definitive answer on the PS3 SuperWhite option - on or off? It seems loads of the threads I've read are anything but definitive :rolleyes:.

Many thanks,
Rob

Some meters like the Eye One Pro and the Spyder2 have counterweights which can be used with LCD screens and put very little pressure on the screen. Set the counterweight on top of the set (taping it in place with electrical tape is a good idea) and let the meter hang down in front of the screen. I then put a weight on the base of the TV or the floor in front of it and set it over the USB cord that connects to the i1Pro. That gets slack out of the USB cable and can help keep the meter facing straight into the screen.
Brightness (black level) control is not the proper control to use to manipulate the gamma. Set brightness and contrast conventionally with the proper test patterns. Then use the 5 pt controls to manipulate the gamma and grayscale. When you have it close, go back and readjust brightness and contrast, then fine tune the 5 pt controls. One last touch up of brightness should then do it.
Superwhite should be on.

Thanks for that Chad, much appreciated.

So I should only be worried about being sure the meter is square on to the screen, and not necessarily touching the screen itself? How far away from the screen would be too far away when dealing with an LCD?

Also, it seems that somewhere between 30-50 ftL is often recommended as a target when displaying a 100% white window on LCDs. Which end of this scale should I be aiming for in a light-controlled room?

Finally, how does the backlight setting relate to contrast/brightness settings – should I be trying to keep the backlight as low as possible (and the contrast slightly higher)?

So many variables…!

You want the display to have the best black level it can have... that implies turning down the backlight control as much as possible. The higher the backlight control, the more light will bleed through the panel - black LCD pixels aren't perfect at blocking light. BUT - sometimes weird stuff happens on LCDs when you turn down the backlight too far. So you may not be able to run it at the minimum setting without getting odd motion or bluring artifacts (or perhaps an unwanted color shift). Also, some ballasts will hum audibly when the backlight is turned down too much and that can be annoying.

Gamma doesn't have anything to do with black level or white level... Gamma DOES have everything to do the luminance response of the panel at every point between black and white. If you can change the gamma of the display by moving the brightness control up and down... that would actually be undesirable. The Brightness control controls the black point. You set the Brightness control with the PLUGE pattern from a test generator or from a test disc - in LCDs, the backlight control MAY be involved in getting the proper brightness control setting also - and the proper appearance of the PLUGE pattern. In theory, you should be able to set the PLUGE pattern with the Brightness control and move the backlight control from minimum to maximum and the Brightness setting would still be correct for every backlight setting - that doesn't always hold true in real displays, but it does hold true in many displays.

THX recommends 30 fL for a 100% white window reading for panel displays in a dark room - this recommendation was chosen because it produces images that are fairly bright, but not so bright that you get eyestrain from viewing in a dark room. Your pupils dilate in darkness, the bright parts of the screen can produce too much light for your dilated pupils in a dark room if you are much above 30 fL. If you have a bias light or if your panel cannot be made dark enough to achieve 30 fL - then you maybe limited to a setting the produces more than 30 fL. If your display can't get darker than about 50 fL, then you'd want to have about 5 fL illuminating the wall behind the display to avoid eyestrain while whatching movies in a room that would otherwise be dark. And that light should be 6500K light or as close as possible to that. And the walls should be neutral gray. Any deviation from that "standard" will alter your color perception.

I thought the i1 meters allowed some distance between the face of the meter and the panel - isn't there a tripod mount on the meter? The owner's manual should specify the preferred measurement distance. I don't like ANY measurement device sticking to any flat panel - in the CRT days when the tube was glass and had no coating on the surface (bad reflections), sticking a puck to the surface wasn't a problem. But once coatings began appearing, I found it was better to simply not touch the screen with anything. LCDs are special because flexing the screen DOES cause problems so not touching an LCD is the only measurement method I'll trust. And because LCD panels contain polarizing layers, you do want the meter well-aligned with the panel or you'll get very funky readings. Sitting off-center and viewing an LCD darkens whites and light grays, and lightens blacks and dark shadows - so only the person centered on the panel and looking straight at it is going to get the best picture - your meter has to be in that same sweet spot.

Thanks Doug.

Right, so I'll turn down my backlight to min and have a play around and see if I can see anything odd happening. Assuming I can't, I'll leave backlight alone and try to calibrate from there. What are the best types of images/scenes I should test the screen with when looking for these artifacts/colour shifts?

The Eye-One (not pro but lt/2 meter) instructions don't specify anything like distance from an LCD screen, so I guess I'll just try and get it as close, central and square on as possible without the meter touching the screen...?

Regards,
Rob

The other issue you may find with the backlight down as far as it can go is that you can't get a good peak white level even with the Contrast control set as high as it can go. So you need to do some checking with the backlight as low possible (or a bit higher to get the peak white level you want).

If you have a test pattern with 0%-10% in 1% steps... that will show you very quickly if the low backlight level is causing shadow detail to be lost.

For color changes with very low backlight settings... just measure the x,y coordinates of a mid-tone grayscale step, like 50%... pick a step that's pretty accurate re. the reference 6500K coordinates. If the x,y coordinates drift as you select lower backlight settings, then the backlight color is shifting as you reduce the level. That may not be terrible - if the display can be calibrated well at a lower backlight setting.

Some LCDs tend to have the visible motion problems with darker colors against darker backgrounds, doesn't have to be super-dark, but say in the 30% or lower range.

If you don't have a 0%-10% pattern with 1% steps, you have to rely on shadow detail in movies - The Dark Knight is a good one but there are many others that are just as good for judging shadow detail and motion artifacts in darker scenes.

You may also find animation like the credits for Casino Royale help show motion artifacts better than normal live action. Some very simple/basic animation may also be useful - Pixar titles (for example), tend to have so much going on in each frame that it can be tough to pick out motion issues.

If they don't tell you in the manual what measurement distances are valid - then I'd contact their tech support department and find out. No sense guessing about something like this. If it is designed to be nearly touching what it is measuring... that's important to know - there could be a difference between 1/2" of space and 1/16" inch of space. The angle of view may be an issue also - one of the probes picks up light to the sides very easily if it isn't close enough to the screen. I don't know enough about the LT to comment one way or another.