Digital cameras, PDAs, color screen mobile phones, laptops, and many other modern portable multimedia devices make use of an LCD or TFT monitor. LCD stands for Liquid Crystal Display, while TFT means Thin-Film Transistor – usually simply just referred to, incorrectly, as LCD, as they appear to be identical to the end user, and they work on the same basic principle. They lend themselves to these applications well as they have very low power consumption, and a lightweight design. These two factors are essential for portable devices like cameras and PDAs because they are designed to be carried around without being a noticeable encumbrance, meaning both the design of the hardware, and the batteries that power it must keep weight to a minimum. While many of the prevailing issues with LCD screens have been addressed over the years, resulting in vastly improved displays for portable devices, due to the fundamental design of this type of display, one thing that still causes problems is the presence of excess light.
As stated above, LCD and TFT both generate a display with the same basic principle. In color displays, the whole of the screen is back-lit with white light all of the time. To change the color of one of the dots that makes up the screen – a pixel – it shifts through varying degrees of opaqueness. The pixel itself can be made to block all light but, say, green, resulting in a transparent green filter. The white light shines through this, however, only the green component makes it through the pixel, and to the viewer’s eyes. The pixel can also shift to red or blue, or if made as opaque as possible, it will appear almost black. One area that LCD screens have never quite been perfect in because of the back-lit design, and the need for the pixels to be able to shift from fully off, where they are transparent, and appear white, to fully on, where they are almost opaque and appear black, all in the space of less than 1 100th of a second, is that the opaque state can never be perfectly created. As a result, LCD monitors always appear slightly gray rather than black.
Compared to what your television, or better yet, a CRT computer monitor can deliver, LCD screens have what is known as a bad “contrast ratio”. This is further compounded when light from outside the screen, such as from the sun, or overhead fluorescent lights shines back onto the screen’s surface. The result is an even worse contrast ratio, causing all of the colors to appear washed out, and indistinct. It is for this reason that your LCD screens are harder to see under bright lights. Most people who find themselves in this situation quickly learn the simple remedy of angling the display down, or using their hand to cast a shadow across the screen. This is always inconvenient, and in the case of digital photography, where a good angle and a steady hand is required, it is often simply not an option. This is where a simple but valuable range of products to combat the problem comes into play.
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