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50hz/100hz frequency????


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Old 14-11-2007, 12:13
meregolfclub
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could someone who knows explain in simple terms to someone who does not the difference an amatuer eye would see in the two frequency modes.
most new updated top end sets are comimg out in 100hz frequencies.
is this good?
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Old 14-11-2007, 12:44
chrisjr
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A bog standard TV broadcast is composed of 25 frames (pictures) per second. For reasons that need not be gone into here each frame is split into two "fields" for transmission.

Each field has half the full number of lines, odd numbered lines in one and even numbered lines in the other. These fields are transmitted at twice the frame rate, hence 50Hz. In the TV the screen builds the full picture by scanning the odd numbered lines then the even numbered lines.

A 100hz TV simply does all this twice over. Basically it scans the screen twice as fast as it would if it were doing it at 50Hz and repeats each frame twice. So in a standard set you see the sequence frame 1, 2 , 3, 4 etc in a 100Hz set you get the sequence, frame 1, 1, 2, 2, 3, 3, 4, 4, and so on.

The theory is that it reduces visible flicker since you are now seeing 50 picture frames per second instead of the 25 in a standard set.
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Old 14-11-2007, 12:54
GDK
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Simple way to spot a 100Hz set: Stand a few feet away from the TV and look directly at something next to the TV, so the TV screen itself isn't in the centre of your vision. If the TV screen appears to flicker, then it's a bog standard 50Hz TV. If the TV screen doesn't flicker, then it's a 100Hz.

For normal viewing, theory says you'll get smoother movement and less judder because of the double display rate. In practice, it very much depends on how well the TV processes the picture to get the 100Hz display. Cheap 100Hz sets can be very poor.

This only really applies to CRT TVs as LCDs and Plasma generate their displays in a different way.
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Old 14-11-2007, 13:32
Nigel Goodwin
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Simple way to spot a 100Hz set: Stand a few feet away from the TV and look directly at something next to the TV, so the TV screen itself isn't in the centre of your vision. If the TV screen appears to flicker, then it's a bog standard 50Hz TV. If the TV screen doesn't flicker, then it's a 100Hz.
You need to bear in mind that only a small number of people can see the flicker - the vast majority can't see it at all.
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Old 14-11-2007, 14:02
edwinastley
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You need to bear in mind that only a small number of people can see the flicker - the vast majority can't see it at all.

And the unwanted picture defects that 100Hz brings along with it makes 50hz a better option in most cases.

100hz sets have pictures that move toward the quality of sd on an lcd - blurry and smeary
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Old 14-11-2007, 16:14
roddydogs
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And the unwanted picture defects that 100Hz brings along with it makes 50hz a better option in most cases.

100hz sets have pictures that move toward the quality of sd on an lcd - blurry and smeary
Thats funny my LCD is not blurry and smeary, but then you only posted that to start up the tired old LCD v Plasma aguments for the 999th time sorry i fell for it.
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Old 14-11-2007, 20:39
edwinastley
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Thats funny my LCD is not blurry and smeary, but then you only posted that to start up the tired old LCD v Plasma aguments for the 999th time sorry i fell for it.
Yes of course ,and 50hz and 100hz are the same aren't they ?:yawn::yawn:

Cant see where you got plasma from? Did I mention it?

Your eyes need testing methinks

Why would I be interested in LCD v PLASMA anyway- with sd they are both crap
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Old 14-11-2007, 21:59
Gilson
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A 100hz TV simply does all this twice over. Basically it scans the screen twice as fast as it would if it were doing it at 50Hz and repeats each frame twice. So in a standard set you see the sequence frame 1, 2 , 3, 4 etc in a 100Hz set you get the sequence, frame 1, 1, 2, 2, 3, 3, 4, 4, and so on.
Er no!? surely these sets have a continuous complete field delay and its 1,3,5,7 etc and on the next field 2,4,6,8etc. but instead of this happenning 25 times a second it happens 50 times a second?

IMHO 100HZ on a CRT gives a "plastic" picture . On an LCD I have yet to see a demo that shows 100Hz to be of any advantage.
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Old 14-11-2007, 22:48
Nigel Goodwin
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IMHO 100HZ on a CRT gives a "plastic" picture .
EXACTLY the term I use for them!.


On an LCD I have yet to see a demo that shows 100Hz to be of any advantage.
Likewise.
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Old 15-11-2007, 08:50
comicsansserif
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Er no!? surely these sets have a continuous complete field delay and its 1,3,5,7 etc and on the next field 2,4,6,8etc. but instead of this happenning 25 times a second it happens 50 times a second?
They are right because they are talking about frames. If you you are thinking in terms of fields then the sequence would be:

50Hz: 1,2,3,4

100Hz: 1,2,1,2,3,4,3,4
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Old 15-11-2007, 12:11
Nigel Goodwin
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100Hz: 1,2,1,2,3,4,3,4
I wouldn't swear to it, but I don't think so?.

100Hz sets write the picture into memory and then read it back to display on the screen - there's no need for it to display as an interlaced image - but I can't say for sure which it does?.
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Old 15-11-2007, 12:49
GDK
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You need to bear in mind that only a small number of people can see the flicker - the vast majority can't see it at all.
You are correct, most people (myself included) don't see the flicker when looking directly at the screen. However, Most people will be able to perceive the flicker if they don't look directly at the screen. Peripheral vision is more sensitive to flicker (but less sensitive to detail) than the central part of the eye.
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Old 15-11-2007, 13:39
PsychoTherapist
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IMHO 100HZ on a CRT gives a "plastic" picture . On an LCD I have yet to see a demo that shows 100Hz to be of any advantage.
You sure you're not just seeing the noise reduction that many of the 100Hz CRT sets have enabled by default?

I have a 100Hz CRT TV and the picture is natural, but when I initially got it it had the noise reduction enabled, thus the consequence was lack of definition, motion blur and a plastic appearance, especially with people's faces. I turned it off pretty sharpish.
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Old 15-11-2007, 14:21
comicsansserif
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I wouldn't swear to it, but I don't think so?.

100Hz sets write the picture into memory and then read it back to display on the screen - there's no need for it to display as an interlaced image - but I can't say for sure which it does?.
Probably explains why they don't look too good to some people then.
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Old 16-11-2007, 07:26
roddydogs
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Yes of course ,and 50hz and 100hz are the same aren't they ?:yawn::yawn:

Cant see where you got plasma from? Did I mention it?

Your eyes need testing methinks

Why would I be interested in LCD v PLASMA anyway- with sd they are both crap
Sorry didnt realise you were a CRT dinasour-still if your happy-good luck (Cant spel dinasor)
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