Grayscale Calibration of Home Theater Televisions - page 2
The most common method of calibrating a grayscale first requires the use of the correct grayscale window images. This can be created with a video generator, or using Ovation Software's AVIA Guide To Home Theater . Avia is an all-inclusive DVD that not only helps calibrate grayscale by providing grayscale window images, but also helps with other video calibrations with an added bonus which includes a vast array of audio calibration test tones. There is a tremendous advantage to using a DVD Test Video for the grayscale generation in place of a video generator. The video generator is great for calibrating grayscale with an HDTV signal, but the DVD allows a real world application where the player and TV can be calibrated together.
When using Avia DVD, the process is relatively simple. You navigate through the menus of the DVD to select the correct grayscale window which range from 0-IRE (black) to 100-IRE (white). In a dark room, with minimum lighting and resulting reflections, you carefully go through each gray window from black to white, and use your eyes to see if the image appears to be gray or have color intrusion. The most common color intrusions seen are red in the darker images and blue push in the lighter images, but please remember this is NOT Red Push or Blue Push. Red Push is related to color and hue, not grayscale. While in each window (black to white), it may be easy to see colors bleed through. If colors are visible, you access the service menu and adjust the correct setting to reduce that color. In some cases, colors may need to be increased in order to make gray look gray. While this process if effective and helps improve the TV's performance, it's not nearly accurate enough to achieve 6500K or D65 as it is more guess work then science. Even the best eyes can not detect enough to determine if the settings are near 6500K as our eye can not accurately detect almost drastic differences in the luminance of bright images such as white.
Calibrating Grayscale using Instrumentation
A more accurate way to monitor and adjust grayscale involves using a sensor and its accompanying software. Two well known companies that provide sensors and software packages include Sencore and Milori. Both have their advantages and disadvantages and can be thought of as almost equal in performance. As most good quality sensor/software packages are out of the working-mans price, it is critical to be sure that the technician you hire uses products like these, or they will likely NEVER achieve optimal performance. It is also critical to use these products in controlled lighting in a room as dark as possible. These sensors are very susceptible to light intrusion which will compromise the measurements. So that tech either needs to be in a very dark room with no windows, or they will be at your house very late an night.
Milori's products were used for the basis of this article. Milori provides two different sensors which includes their EyeOne spectroradiometer, or Trichromat Colorimeter, both operating with Milori's ColorFacts software. Sencore provides a similar Colorimeter Sensor with their CP5000 and ColorPro Software. Either of these packages are an essential tool for trained technicians who make a living doing Home Theater installations and/or calibrating TVs. These sensors hook up to any PC via a USB port and their accompanying software runs in Windows.
What's interesting is that ColorFacts lets you decide how the grayscale images are created; you can choose to have the computer generate the images, or you can generate them externally using a test disk like those on the Avia DVD. There are pros and cons to each method.
Using the ColorFacts Grayscale Wizard
The powerful Milori ColorFacts software package contains a host of wizard menus that guide you through set up of the sensor, taking measurements from the TV and reporting results based on calibration images displayed on the TV. It even has its own grayscale generator that works automatically with the sensor. Just one click, and ColorFacts starts grayscale images from 0-IRE to 100-IRE in 10-IRE increments, and at each increment, it automatically measures the resulting luminance. In a matter of a few minutes, you have a complete read out of the entire luminance spectrum of the TV. While using Colorfacts built-in gray scale test images may be the easiest method, it may not be the best suited for your system. This is because the signal generated by the computer may not match the signal generated by the home theater DVD player or HDTV receiver. For more accuracy, you should consider generating the patterns externally using a test DVD. The Grayscale Wizard is best used for calibrating the display monitor on your PC, not necessarily your RPTV or Front Projector.
Using the DVD Player to Generate Test Images
For me, the primary reason for calibrating the TV is to create the best image possible especially for component video input from my DVD player. The DVD player coupled with the Avia Guide To Home Theater creates a powerful image generator tool that works extremely well with either the Sencore CP500 or Milori CF6000 systems.
When dealing with DVD players, it's important to note that the output signal generated from a DVD player varies from model to model. For this reason, calibrating the grayscale using a player will be somewhat unique to the player used in the calibration. If another DVD player is substituted in the system, the grayscale image may be slightly different. Regardless, there is an advantage in using the DVD player for the grayscale source. By doing so, you are actually calibrating the system with the very source that you will be viewing DVD movies, thus allowing for optimization of the Home Theater System. There is a word of caution however. Many of the newer DVD players have video enhancer's built in. These enhancer's tend to exaggerate colors. Prior to calibrating, be sure to turn off the extra enhancement modes as they will create inaccurate results.
When using DVD as the source, the ColorFacts wizard guides the user through the Avia Guide To Home Theater menu to find all the grayscale images required. This method is a bit more tedious and requires special attention as you navigate through the grayscale images on the DVD player and use the PC to activate the sensor and take a reading. If you're not paying attention, you may accidentally hit the sensor button on the PC without changing the grayscale image on the DVD player, thus making you have to start all over again. It's also worth noting that the darker images take the sensor longer to measure then the lighter, so the wait time between selecting grayscale windows will vary. Ovation Software's Guide To Home Theater is somewhat challenging to navigate because this version does not display chapter and title. Nevertheless, when time and caution are taken, this proves to be a more accurate method of measuring grayscale.