A Beginner’s Guide to Display Calibration

This guide is work in progress. I will update with pictures as time goes by, please be patient.

What is Calibration?

Calibrate - To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument)

Calibration - The act or process of calibrating or the state of being calibrated.

Display calibration is centred on calibration of your display to standards.

Movie studios/directors adhere to standards when mastering movies/films.

One key feature of the standards for movies (colour) is the white point. The reference white point is defined as D65 for both North American and European standards. The white point refers to an x,y coordinate of 0.3127, 0.329 in the CIE Chromacity chart. CIE(Commission Internationale de l’Eclairage) is the international body responsible for the measurement of color.

6500K however, is a measure of the correlated colour temperature (CCT) of the white. Where D65 specifically targets a white point, the colour temperature is slightly misleading. It is possible to have a white that is 6500K in colour temperature (as it depends on whether the red and the blue channels primarily) but not hitting D65 white. For all practical purposes, D65 is a better representation of calibrating to a standard as if you do hit the 0.3127, 0.329, you automatically hit 6500K CCT.

The different standards that are available out there are:
· ITU-R Recommendation BT.709 (“Rec. 709”) – the standard for both North American and European high definition television - HD
· ITU-R Recommendation BT.601 (“Rec. 601”) and SMPTE-C – the standard for NTSC 480i/60Hz standard definition television (SMPTE-C has supplanted Rec. 601), and
· PAL/SECAM – the standard defined by the European Broadcasting Union (EBU) for 576i/50Hz standard definition television.

Once a display is calibrated to these standards (or as close to these standards as your display will allow) you do not need to wonder if the picture is accurate and tweak your settings for every movie. If your post calibration results are good, the pictures that you are viewing are as close to what the director intended for you to see.

This post has been edited by anfieldude: May 10 2010, 02:03 PM

Key Components/Terminology

1. Brightness
2. Contrast
3. Sharpness
4. Colour (Hue, Saturation, Lightness)
5. Tint
6. Greyscale
7. Gamma


In order to carry out basic calibration, you would need a test disc and preferably colorimeter/spectrophotometer/lightmeter & calibration software.

Test Patterns
Test patterns or test discs are needed for you to set some of the basic stuff even without a meter. I would recommend the free AVSHD709 (for HD sources, Blu Ray and Media Players) or TomHuffmans free NTSC DVD test patterns. You can also purchase the GetGray test disc (available in PAL and NTSC), DVE HD Basic Calibration Blu Ray/DVD or the fantastic Spears and Munsil HD Benchmark

We will discuss the most basic component of display calibration, one that can be done without any meters (most of the time)

Setting Brightness
Brightness is actually the setting of the black level that for me is the basis of a proper calibration. My preference on the test pattern on setting brightness would be the brightness (PLUGE Low– Picture Line Up GEnerator) pattern on S&M Test Disc. However, since most of you would not be buying the test discs all the explanation would be based on AVSHD709 free test disc. Pull up the Basic Settings, 1st pattern (called brightness and contrast). On this pattern you will see flashing bars labeled 1-25 against a video black of 16. First check that you cannot see all the way down to the label of below 5. If you do these bars flashing, you need to check the settings of you Blu Ray player or your display. What is probably happening is that you are sending a RGB Full signal (also lookout if your display has a setting for 0 IRE, 7.5IRE, select 7.5IRE for the correct setup). For all BD or DVD material, it is based on a video level setting of 16 and above. This is the 1st setting you need to check. Once you select the correct output from your player (typically most players have an Auto setting, this setting normally sets to YCbCr it depends on the EDID that your display is sending out), you are ready to set the brightness. It is better to set the brightness in a dark environment. Turn up the brightness until you can see the bars below 16 flash. Then turn it down until 17 can barely be seen. Now go to the next pattern. The next pattern is brightness and a contrast pattern together. For displays that have different outputs based on dark/bright content in the same screen (plasmas, crt) check your brightness setting that you set earlier. Same method used here, in this case see if you can get at least 19 and above flashing and the 16 and below not flashing. The correct brightness setting is the higher one from pattern 1 and 2. ie, if using the 1st pattern you got a brightness of +1, and on the 2nd pattern you got a brightness of +2 then , use +2.

This post has been edited by anfieldude: Apr 8 2010, 03:12 PM

Setting Contrast.
Setting of contrast on a digital display without meters is difficult, as most digital displays do not clip white levels above digital white of 235. Pull up the contrast setting pattern on the AVS HD709, 3rd pattern on the basic setting page. You should be able to see as many bars as possible above 235. If you do not see anything above 230 then your set is clipping whites. Else adjust contrast up/down to show as many bars above 235 as possible. Most digital displays will show quite a bit above 235. Another thing to look out for is if the contrast is set too high, the whites start to look reddish, bluish or greenish. In this case, you need to set contrast in tandem with another pattern. In the Misc Patterns, go to the RGB High Clipping. This is essentially a clipping of the individual RGB channels that make up white. The problem with turning up contrast too high is that some of the individual channels get clipped. This in turn, makes the white either too green, red or blue. Turn down contrast until the all channels clip at about the same level.

If there does not seem to be any clipping at all for white, red, green & blue channels (highly unlikely as all digital displays will clip one channel or another), set contrast using a 100% white window (from either Calman window patterns or HCFR window patterns) to the level that pleases you eyes and is not uncomfortable.

Setting Colour/Tint
I am not going to go into this as unless you have a filter it is impossible to set this by eye. Even with a filter, the best way to set colour is to use a meter. I will add this if there is a need for this. I will explain this later as it is a complex matter.

Setting Sharpness
Setting sharpness is pretty subjective. Using the sharpness setting and the sharpness test patterns, play around with the sharpness settings to get as sharp a picture as you can while looking for halos or white edges near the black lines. Also look out for moiré and lines that seem to merge. Also, select the picture mode that reduces the artifacts. All displays have various modes, ie, dot by dot, just scan, full, wide etc. In most cases, dot by dot is the one that normally has zero over scan. Play around with them to see which one gives you the least artifacts with the sharpness setting. The Spears and Munsil disc has a better pattern to set sharpness and I have tested it with various displays. The adjustments you make in the display responds well to what you see in the test pattern that makes setting sharpness easier.

That about covers the basic settings that you can carry out without a proper meter. In order to carry out a complete calibration, you need to have a meter and complete the calibration of greyscale, gamma and colour.


This post has been edited by anfieldude: Mar 23 2010, 08:21 AM

The next few areas require the use of a colorimeter or a spectrophotometer to set correctly. I will explain these briefly for now and add more detail when I get the time to complete the documentation

Greyscale
Greyscale is the calibration of the shades of white. White is the basis of colours, greyscale calibration is done to set the white shades correctly. Typically, the display controls that calibrate greyscale are labeled as white balance and have Red/Green/Blue bias/cut/gain/offset/high/low. They control the individual RGB channels that make up white.

Gamma
Gamma is a luminance measurement. This is a measurement or parameter that controls the light levels are different input levels. Setting gamma correctly is essential to the “3D” pop that people look for in a digital display. Gamma is commonly targeted by calibrators range from 2.2 – 2.5 but this depends purely on your viewing environment. Lower gamma is normally selected for high ambient light surroundings and higher gamma is for darker environments. I find targeting a gamma of 2.35 is best for semi dark environments and 2.15 for bright environments. In a dark room, a set that tracks gamma correctly at 2.35 with good black levels will produce an image that is very 3D, especially if the set also tracks good greyscale.


This post has been edited by anfieldude: Mar 23 2010, 08:23 AM

Colour/Tint
Colour is a whole new can of worms. There are set colour points in the CIE chart for each colour. Red, Green and Blue are the primary colours and Cyan, Magenta and Yellow are the secondary colours. To do a proper calibration of Colour using a Colour Management System would require the use of a Spectrophotometer (colorimeters are okay as well, its just that the spectros are supposedly better in them). Each colour has its own theoretical Hue, Saturation and Lightness. The Hue and the Saturation are represented in the CIE Chart that I described earlier. A display with a good CMS would typically have independent controls to move all of the above.

The Colour controls on the different sets behave differently. On some sets, the colour control effects saturation and on others they only control lightness.

The Tint controls normally just rotate the secondary colours, however, it depends on the implementation of the display.

Saturation is a measure of how far away from the white point in the CIE chart is the particular colour. If the colour is over-saturated, it means that it is further away from the white and as such seems richer.

When hue is off, the colour seems to resemble more of a another colour rather than itself. Eg, Cyan’s hue seems to be shifted towards green instead of blue, meaning that the cyan seems to have more green than blue.

Lightness is a measure of how bright the colour is. It is possible for a colour to have accurate hue and saturation but because the lightness it wrong, it seems too bright.

All these parameters are those that are needed to be right in order for the colours to be correctly decoded accurately. I have seen numerous displays that have no controls for a CMS and the basic colour and tint just do not do much. Then, there are some displays that have all the controls you can imagine. I hope in the future all display manufacturers provide a full 3D CMS that the consumer can use to fine tune his display.


This post has been edited by anfieldude: Mar 23 2010, 08:25 AM

The one thing that has happened in the past couple of years is the emergence of affordable home theater enthusiasts calibration packages that allow more and more people to calibrate displays. Along with this, the masses are adopting and understanding that calibration actually improves the overall home theater experience and adds to the excitement. With a properly calibrated set, you do not need to wonder if the pictures you are viewing are off and you can enjoy the movie more.

The choice is yours, you can either become and enthusiast and buy your own calibration software/hardware, or you can hire someone to do it for you so that you do not need to invest into this area.

I have been using Calman software for the past few years to calibrate displays of family and friends. I have been very happy with the support I have gotten from the team. The link is provided below and they ship to Malaysia.

SpectraCal Website

Another newcomer to the enthusiast and professional calibration arena is Chromapure. Their software is slightly different and their up and coming in the industry.

Chromapure

These are the 2 affordable solutions I know out in the market.

I have used Calman for a couple of years and have been following their growth for some time. The enthusiasts are lucky to have affordable solutions for home calibration with both of these players in the market.

This post has been edited by anfieldude: Mar 28 2010, 04:19 PM

cool... finally the thread we've been longing for... nice work from calibration guru anfiel...

Fianlly, guru give lesson to all of us.

Nice write-up, guru. Thks for the effort.

Mods please sticky this.

Thanks for sharing

TQ boss

Hi..

To those who are reading tis thrd n hv no inkling wat he is talkin abt .. I d suggest Pm bro A and ask nicely so he ll calibrate ur display for you..

Kudos to bro A
D

Thanks for your efforts bro...

goodjob

master of display calibration gives lesson here...ya pls sticky it...

Please give me some time to improve on this thread. I will be doing bit by bit. Also if there are any questions, pls ask here and I will answer and improve on the thread documentation for ease of understanding.

nice work bro and thanks for the introduction to start me up on calman calibration through the phone.

anfield, respect

pinned on top!! good sharing!