CONTRAST RATIOS OF DISPLAY SYSTEMS
When shopping for a new projector or other video display devices, an important specification you will be comparing is the specification sheets of these display devices and there contrast ratio rating.
Contrast ratio ratings differ from device to device so it is important to understand what a contrast ratio rating is and how it is calculated to ensure you choose a device that is right for your specific application. This Projector Source Canada article should help you understand how the contrast ratio ratings are defined, the differences between ON/OFF contrast measures and ANSI contrast measures, and the differences between static contrast ratio and dynamic contrast ratio.
What is contrast ratio?
A display device''s contrast ratio is a ratio of luminance, and refers to the ratio between the brightest and darkest colours - ie white and black - that the projector can output. A typical contrast ratio is 1000:1. In order to understand what this number means, view the first number as how much brighter the brightest colour is when compared to the darkest colour. In this case, the lightest white colour that the display device can output is one thousand times brighter than the darkest black colour it can output.
ON/OFF contrast measures
Some companies measure the contrast ratios of their products by comparing the amount of light that is output when displaying a completely white image (on) versus the light output of an all black screen (off).
You will find that the majority of display device companies employ this measurement technique since it results in a far higher contrast ratio figure than the alternate ANSI contrast measurements (described below). This ON/OFF technique is not necessarily the most accurate method of measuring contrast as nobody watches a screen that is completely black with no image. As soon as any sort of image, no matter how dark, is displayed when the device is turned on, light will begin to reflect and increase the back levels, thus reducing the contrast ratio.
Static contrast ratio
The static contrast ratio of a device can be measured by using the American National Standards Institute (ANSI) test, which simultaneously measures luminosity values. This is achieved by dividing the screen into a checkerboard of sixteen white and black squares then dividing the average luminosity of the white squares by the average luminosity of the black squares. While this is thought of as a more accurate way to measure contrast ratio, there is potential for the room''s environment to influence the test if the measurements are taken in less than ideal conditions.
Dynamic contrast ratio
Dynamic contrast ratio is a recent development in the technology of LCD display devices. What differentiates a dynamic contrast ratio from a static contrast ratio is the time period used to measure the brightest whites in a brightly lit picture displayed in comparison to the darkest blacks in a dimly lit scene.
A static contrast ratio is used to determine the contrast ratio at a single point in time where as a dynamic contrast ratio is a measurement over an extended period of time. This results in a far greater contrast ratio figure, meaning that a static contrast ratio of 2000:1 will produce a far brighter image than a television with a dynamic contrast ratio of 10000:1.
What contrast ratio do I need?
Many consumers make the mistake that a display device with higher contrast ratio rating is automatically the preferred choice for a better picture. In fact, the contrast ratio required depends on the environment you are planning to use the device in, and what you intend to display with the device. If you are using the device in a room with a large amount of ambient light, a higher contrast ratio rating is advised to ensure that you can see the image properly.
In terms of the types of image being displayed, home theatre enthusiasts will prefer higher contrast images as it can improve the picture quality by rendering deeper blacks. On the other hand, a lower contrast picture is preferable for business presenters giving presentations including Excel spreadsheets or PowerPoint slides that are predominantly white.
Contrast ratio buying advice
It is difficult to effectively compare the contrast ratios of different devices because manufacturers do not stick to one standard of measurement to work their contrast ratios out.
The price of a projector, or any other video device is directly proportional to the contrast ratio of the device.As we have shown, sometimes a lower contrast ratio can be preferable. DLP projectors tend to have a higher contrast ratio than LCD projectors of the same price. Conversely, in terms of televisions, LCD televisions characteristically have a greater contrast ratio than Plasmas. As the technology between these two types of device varies so much Plasma televisions already render richer pictures with deeper blacks, thus alleviating the issue of a lower contrast ratio.
We hope you enjoyed this article by Projector Source Canada. For more information or to purchase a display and projector for your business or home, visit us at http://www.projectorsourcecanada.ca
or contact us at 1-800-821-3021.
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