The frequency sweep of the screen: 50 or 100 Hz

What I'm going to tell You, You will find nowhere this information is a secret and not like the one who's fully online, believe it or not - decide for yourself. Ready?, then we'll start bf

Stogursey TV, it's cool!!! ai Yes, it sounds.., the words 100Hz emblazoned in the foreground, so it was good to see... You've already read about modern TV with picture tube inside? This material is a continuation of the article about sunrise and sunset CRT TVs

So, what is 50 or 100 Hz, let's consider this question, especially because this topic is relevant not only for old TVs, but also for modern LCD, LED and plasma ab Let's set aside terms such as FELL, SECAM and NTSC, they will be discussed in a separate article, but here we'll talk about the scanning frequency

So we could see moving objects on the screen as in life, our eyes (because of their inertia - the ability to temporarily remember a picture) you must provide at least 24 fps. Ie, if the picture in front of our eyes will change 24 times a second, we will not see the sequence of pictures and one that changes smoothly. This principle is laid down in any ordinary "film" the movie that we watched in the cinema (about the effect of "25th frame" will not speak here)

The first movie was shot on film with a frequency 16 frames per second. (remember Charlie Chaplin and his Comedy ad ), however, movement actors were deprived of the smoothness, they were intermittent, especially in a dynamic scene (when a lot of movement and they are fast). So, in consequence, it was decided to increase the number to 24 frames/sec. With same frequency were filmed on film until recently (note that, you will soon realize why bs )

Another caveat, is film in the camera (recording and transmitting) came not smoothly, and jerks" (frames): the camera lens was frame, was delayed some time (there was a process of "photographing") and quickly changed the following, which again was delayed for some time (much more than a time frame). Now, when we remember the basic concepts, you can proceed to scan TVs

How have you formed the image in the TV? Let's start with the interlace. At a frequency of 50Hz, we get 50 "pictures" per second. First, the TV receives the information on the odd-numbered rows and the rays of a CRT (red, blue and green) prescribe them on the screen, starting at the top (1, 3, 5...625) and to the bottom, then beams back up and begin to draw even lines (2, 4, 6...624). It looks like this:

scanning Frequency display: 50Hz

The phosphors used in television tubes, has a certain inertia (persistence), it may not light up instantly and even more, instantly extinguished, however, by the time of the "drawing" of the second frame, which was painted at the beginning of the first frame - has become less bright ac (although, in confidence, the information in this figure, to put it mildly, exaggerated, not so much the brightness of the extinguished al )

This means that one frame (picture) is formed on the TV screen of the two "half images". Our 50Hz is 50 frames (pictures) per second, and frames (more precisely - polyedra) 1 and 2 , 3 and 4 , 5 and 6 can be the same (if you watch the film, lapped with film) or different, depending on the recording method of the image. It is important to remember that in each of the 50 fields is the only half of the rows of (there are 312 and not 625)

How is the picture 50 Hz

If the image is not formed by two "half pictures", and one frame (lines were prescribed to consistently: 1, 2, 3, 4...), then, by the time the rays will begin to draw the bottom line, what has been "drawn" in the first lines - that's dark would be strong enough (brightness at the top of the screen will be smaller than bottom)

Of course, strings can't overlap perfectly, so the image is slightly different from the original, but! not as much as You all talk, showing off these pictures:

Interlaced

Much often such a phenomenon as "interlacing images on the screen of the CRT was associated with a poor signal (recorded on a crappy VHS) or problems in the block of chromaticity of the TV. When I, long ago, set in your "Slavutych C-281" 1991 year of release, an advanced new module chromaticity (model I do not remember, and to open a working (!) TV - lazy ah ) with an additional system definition, I was amazed at the new quality paints shock , but it was still the same old TV with a refresh rate of 50Hz. See for yourself, You see this "creepy corestack", which You all heard in the other articles? Correctly don't see and I don't see (a screenshot of the screen with my regular TV) bn

Phosphor on the kinescope

At the same time (1995 - 2005) were placed EN masse in a TV decoders PAL (for the first cable or Vidic) and they can see the difference: quality decoder or not. If he was "not very", then the image was actually striped, despite all attempts to configure the decoder ac

It should also be noted a small flicker images, particularly in stationary subjects (which You are well familiar on old CRT monitors), frame rate (or rather fields) is clearly not enough, so the appearance of TVs with a refresh rate 100Hz was "welcomed" by. If to deliver nearby two TV's (normal and 100 Hz), the difference in definition (in a still picture) was significant and this pattern is not lying, however, isn't that the case?

Interlaced and progressive scan

But let us leave monitors, it has its own nuances and back to the TV. At progressive scan beam registers the image sequentially in each row: 1, 2, 3, 4.... 625 (for regular TV), so the image is formed at once, as a whole, not in a line. In this case, the refresh rate: 100 times per second (two more than 50Hz TV). That's how beautiful it (the idea) was supposed to be:

the Difference between interlaced from progressive scan

But then the fun begins ad just want to warn you, if someone can watch the disk on which recorded ten films and sees no point in waiting license, and content ekranai - on do not read bt

So, here we sit at home, smarten the TV and there advertising: "stop watching the old TV, buy a new one with 100Hz scan and you will see a new quality....", while such advertising is usually shown here are frames, so we better see the difference:

Advertising TV 100 Hz

It was a great publicity stunt and many, during this advertising, really forgot that both of these pictures (ugly, especially the blurry and pretty clear), they saw same your "old TV" bk But it's all in the quality of the recording signal. I'm sure You notice how is always more colorful and juicier than movies, TV shows, and cheap soap operas, as the money is paid yet and not small, there as no one saves, and "soap Opera" was shot on cheap film stock

Now in all the stores the TVs are connected to the receiver or DVD, and not simple, but HD quality, but it was not always, before they were all configured and connected to the usual air antenna or cable TV. The rejection show You sellers pictures from simple analog signal was forced, as the TVs have forgotten how it normally take

One of the biggest disappointments, comprehend owners of new 100Hz TVs, was advancing when they connected it at home to your signal source (antenna or cable). People called and asked the master to come and set up their TV to show the way in the store. What was wrong?

Watch the news: at the bottom are subtitles, just not smoothly, and jerks (quickly move your mouse and follow her with his eyes after half a minute eye fatigue guaranteed), where is the promise of 100 Hz-Wai clarity??? ai

Digital brake TV

And the speaker?, well, no, the background of a news Studio, a Desk speaker, the decorations - they really look great, clear and beautiful, but her face shown close-up.... Where the moire and pop-up spots on the face?.., I want to go away, watch TV in the usual distance for the eyes becomes a problem ac

Narushenie color

Football? Yes, as "promised" in advertising, the ball is clear and beautiful, and the trajectory of its flight (probably in gift) is also fully visible, from the moment of impact until the fall ag These photos are relatively "good", in reality, when viewed with the conventional antenna, the ball was "smeared" even more:

Blurry object

If a channel is "rippled" - it was just a quiet horror, as the TV in good faith prescribed every pixel of this "ripple", trying to highlight it as clearly as possible, but the ripples, called "white noise" is not static, it is constantly moving, and much faster than the main signal, the TV simply did not have time for it and the final picture is "funny"

the picture Quality during bad signal

However, when it was stationary or slowly moving object, provided the perfect signal, progressive scan would undoubtedly win, and the first equipped with the 100Hz - it was the thing ay although digital brake totally absent in ordinary TVs, and there was a little visible

If You are wondering where did these "brakes" on the image in the "digital" 100Hz TV and why, instead of improved quality, everything turned out the opposite, read the second part of the article: digital brake or the curse of digital processing of analog signal

Simple TVs with interlaced 50 Hz, then sold in shops, showed even worse: the sound could be quiet and disappear even with a great signal, paint, poisonous and unnatural, and the quality of the correction, focus, and information beams in the kinescope is generally any one of the gates did not climb....

If You happen to be the owner of (or have seen friends) some old Gruendyke, Phillips or Sony, provided that he had a good signal, you probably noticed that the image as a living, paint is just amazing, and the sound could remain pure even in poor signal from antenna bs

circuit design good channel

The reason was simple: high-quality filtration system and image processing with sound inside the TV. But in those modern television sets that were on the shelves next to new "stewartsville" - this was not. More and more filters and maintenance items began to push into a single chip, of course, the details became more accurate and smaller, but the quality of the processing of the analog signal is gone forever

Link to this story: http://en.rem-tv.net/publ/3-1-0-41

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