The difference between the brightest and darkest parts of the scene, known as contrast.The bigger this difference is better the contrast.
Contrast in general is a function of the ambient light. (contrast = 1/ambient light)
More ambient light means less contrast and vice versa.
ambient light = 10, contrast =0.1 (B'coz , contrast = 1/ambient light)
ambient light = .1, contrast =10 (B'coz , contrast = 1/ambient light)
Factors Affecting Perceived Contrast Ratio
The Human Eye
The human eye, at any particular instant, can perceive contrast ratio over a range of 400:1 to 10,000:1 according to numerous references. However, the human eye is a dynamic organ and can adjust, both chemically and via iris movement, over some 30 minutes in steady light conditions to perceive higher contrast ratios of up to between 1,000,000:1and 10,000,000:1. One can think of the eye as an adaptive detector. Age is a factor influencing what contrast ratio might be perceived by the particular individual.
The images displayed can affect the perceived contrast ratio with the human eye being able to detect higher contrast ratios for static images as opposed to moving images.
Ambient Light Conditions
Even small amounts of ambient light (one LUX ?? a candle flame) significantly reduces the ability of display devices to render higher contrast ratios (in the 1,000??s). A black area can only be as black as whatever incident light is reflecting from it. You cannot ??project? the color black. Doubly detrimental is the rapid drop off of the eyes contrast sensitivity with higher ambient light levels.And what do doctors say never watch TV/HT in complete dark, not good for eyes.So if u will see TV with ambient light with 6500k colour temp. In this case (of ambient light environment), as screen materials that are used in a LCD TV are much flatter in texture and lower in reflectivity, makes an LCD show better contrast in a brightly lit environment so LCD is a good choice.
The eye is sensitive to the spatial frequency which is a factor related to the distance between the contrasting image elements in relation to each degree of field of vision at the eye. Consider that the frequency is the count of the number of alternating vertical stripes of black and white across an arc of one degree with the eye as its origin. Increasing the number of vertical stripes across the arc (making them thinner) will, beyond a certain point, reduce the eyes ability to perceive contrast ratio ?? even though the actual contrast between the white and black stripes remains the same.
Watching TV in the dark
Why is it stressful to watch TV during nights with all lights switched off?
R.P. Ram Mohan
Answer 1: The human eye has a variable aperture called the pupil to regulate the amount of light entering the eye.
The size of the pupil is controlled by a set of muscles called the iris. The iris contracts in bright light to decrease the size of the pupil.
In darkness/dim light, the iris relaxes completely so that maximum amount of light can enter the eye through the enlarged pupil.While watching TV in dark/dim light, the TV becomes the lone source of light entering the eye.
As various pictures/scenes are continuously shown on TV with constantly varying degrees of brightness, the iris is made to constantly relax and contract, thus causing great strain to it.
This effect is not felt when TV is watched in light, since the TV is then not an important source of light and the impact of its fluctuations in brightness is negligible.
Answer 2: While it is stressful to watch TV in darkness owing to the constant relaxation and contraction of the iris and hence recommended not to watch TV in darkness, the same does not apply to watching a movie in a dark theatre.
The simple reason is that movie, unlike the TV or computer image is not in the form of pixels. Movie is in the form of analogue.
A simple way to check for the stress caused to the eye is to see how stressful it is to read a long article on a computer compared with reading the same article from a print out.
When we read a book, the letters are completely black and the space between letters is just plain white. On a computer, the central part of a letter is darkest and the colour reduces towards the edges and drops off. So the focusing mechanism is put under a lot of stress.
Again, in the case of watching movies in a good commercial theatre, the stress caused to the eyes is less as the eyes' field of view is completely occupied by the screen, that covers the entire front wall, and for the rest of the theatre there are dim lights all over the place.
This is not the case with TV or computer. The screen is smaller and does not fill the complete field of vision of the eyes.
Moreover, the object on the TV is constantly flickering and we see areas that are of different light intensities.
Hence, it is highly recommended that watching TV or working on a computer be done in a well lit room.
Dr. Arulmozhi Varman
Uma Eye Clinic, Chennai
R.P. RAM MOHAN
Newer LCD's have better colour accuracy now---->not much of a problem
except ur point for black levels
, none of your point supports the LCD as all the other points including strain from anything tht focuses light in a room, even tht is there with a torch light too...
Now regarding your black levels point, then buddy your theory is not complete from the TV point of view...
if you know the technologies, then
LCD, works on the same technology as CRT, as it tool have backlight, and the when the rays from tht, crosses the RGB color panel chips, to the LCD Panel, then the dried up states of Liquid Crystals, expand them into pictures...
Where in Plasma, there is nothing like RGB chip, or backlight...
A Plasma panel is filled with Neon Gas, which in dried state has RGB color pallete with dried neon...
And when it gets positive & negative current from both the ends, they pat on the particular pixel, which thus expand the RGB color to make the proper color of tht pixel...and hence generated the picture...
Even now if u havent understood the theory.. then let me tell u...
In case of LCD, when the light is thrown through RGB panel, to the screen, to pixels, they have almost the same colors, so the number of colors go less... Though the contrast ratio is said to be the same, but more only because of the technology, and in that as well u require pretty bright ambience to get the proper view, as is there in Showrooms..
But, in case of Plasmas, the picture is generated on due to current charge on the pixels, so they can get as darker as they get the power, and as light as the power, as the RGB has all the colors of the Universe...
And where in homes, the ambience is totally different from the showrooms, the picture is clear, with much more colors than LCD...
anyone can put a LCD or a Plasma side by side and do this experiment...
Now, regarding the light in the room, tht the room, should nt be darker...in this plasma states much better than LCD..
as lcd technology has backlight coming from back, it directly get into your eyes, which annoys a lot, where plasma generates its own picture, so there is no problem with tht..
anyone can do this experiment as well..have a look at a Plasma in a dark room, then open the room lights at once..
Then do the same with lcd...
you will find tht, the lights while watching movies hurts a lot, in case of LCDs..
Bro, be practical on points, then be on theory..
Your theory is not wrong, but is in normal factor, but when its combined with other technologies the effect is different...
same as drug when taken directly kills, but when given as a medicine heals...