confused about contrast ratios

On Sat, 05 Jan 2008 00:44:01 GMT, Dave Farrance
wrote:

Mike Henry wrote:

In , "Zimmy" wrote:
Personally, the problem I have with cheaper/older LCDs is too much contrast,
ie all the brightest shades get rounded to pure white and all the darkest
shades get rounded to pure black

Er, those two problems you describe are called "black crushing" and "white
crushing", not "too much contrast"(!) I think it's important to get the
terms correct since this is a technical group...

Is there any other effect of "too much contrast"?

Loss of information towards extremes of light and dark is the most
obvious effect of increasing the contrast of a given image, but that's
a very different thing from the contrast ratio of a display device,
which is what this thread is about. High device CR can handle high
image contrast, roughly speaking, everything else being equal, which
it usually isn't.
--
http://www.robinfaichney.org/

Klaus Kramer wrote:

thanks to variations on HDMI video level standards (normal/extended),

Does this have anything to do with DVI not using all the levels that
HDMI does? For example (and I'm making up the numbers here because I
don't remember them) if HDMI has black at 0 and white at 255, DVI will
have black at 16 and white at 239 or something like that. I read about
this once and have never heard of it since.

On 2008-01-05, Klaus Kramer wrote:
Dave Farrance schrieb:

Is there any other effect of "too much contrast"?


Please look at my answer some 10 lines above...

Your post does not appear to be in reply to
(directly or indirectly) any previous post of yours.

So you haven't written anything "above"...

--
David Taylor

"Alan Pemberton" wrote in message
rve.co.uk.invalid...
Klaus Kramer wrote:

Dave Farrance schrieb:

Is there any other effect of "too much contrast"?


Please look at my answer some 10 lines above...

Is that even lines or odd lines? Because the tenth line above your text
reads "X-ID: GFwL-OZFgeyDAwAJShZxcUS6EvDU2JkRfNqy-awbTtGMYD5WtYVWY2"

He's just trying to baffle us with science.

Bill

In article .co.uk.invalid,
Alan Pemberton wrote:
I have seen both correct and incorrect descriptions in textbooks and*
magazine articles, and it must confuse people who are new to it. For a
superficial understanding of how interlace works you could argue that line
numbers are not important, which is a fair point. However it becomes*
important in the context of actual equipment that has to generate or read
signals on particular lines, because it is then vital that everybody agrees
upon which lines are which.

And which field is which. Compared with other standards (and common
sense) the 625 line system seems to have its odd and even fields in each
frame numbered wrongly (first is even, second is odd), but it all hangs
on the definition[1] of 'even field' and 'odd field'.

An odd field is one in which the first picture line is a whole line, an even
field is one in which the first picture line is unblanked halfway through.

The more modern system gives the fields numbers, starting with the one in which
the beginning of the field pulse coincides with a line pulse.

Thus one labelling system is defined in terms of pictures, the other in terms
of pulses. If there is a whole number of lines between the beginning of the
field pulse and the start of picture, as in 525/60, then they agree, but if
there is an odd number of half lines, as in 625/50, then they don't, and we are
left with the oddity that first, third, fifth and seventh fields are even,
while second, fourth, sixth and eighth fields are odd.

Rod.

In article , Mike Henry
wrote:
Indeed. My main point was that Simpsons was wrong to suggest that
interlacing always means there are 25 pictures displayed per second.

You're right of course. It depends on what they put on the lines.

Rod.

In article , Robin Faichney
wrote:
Is there any other effect of "too much contrast"?

Loss of information towards extremes of light and dark is the most
obvious effect of increasing the contrast of a given image, but that's
a very different thing from the contrast ratio of a display device,
which is what this thread is about.

As with almost anything else that used to be regarded as a technical
fault or misalignment, this is now often perpetrated deliberately as an
artistic effect. At least I think it's deliberate, most of the time.
Black crushing so that dark clothing simply blends into the background,
accompanied by some desaturation at low brightness levels, appears to be
a particularly fashionable gimmick at the moment. If you're watching a
programme that has been made this way, the contrast ratio of the display
won't matter at all because the detail that has been crushed in the
camera no longer exists, so nothing can display it.

Rod.

"Mike Henry" wrote in message
...
In , "The Simpsons"
wrote:

"Mike Henry" wrote in message
. ..
In , "The Simpsons"
wrote:

A standard CRT screen is refreshed with only half an interlaced picture
in
1/50s therefore with a complete interlaced picture every 1/25s.

No, that's only if it's a special mode called IIRC segmented frame (two
halves of a 25 frames-per-second picture). That gives you jerky 25 fps
motion, like the "film effect" that some producers are in love with.

Normal interlaced TV pictures, as stated, are nice and smooth at 50
fields
per second. In one 1/50th of a second the even lines are displayed, and
in
the next the odd lines, and so on but each pair does is not making up
two
"halves" of a jerky 25 frames/second picture. There are 50 different
movements per second that are recorded by the camera and displayed on
the
screen. (It is this smooth motion that we've had for many years that the
cretins are trying to take away from us.)


See this link, look under DESCRIPTION
http://en.wikipedia.org/wiki/Interlace

No thanks. If you think that there are only 25 movements per second,
discuss it here.


Now why would you be afraid to look, it's quite legitimate to post a link in
a newsgroup to make a point.
BTW I've said nothing about movements per second but that two interlaced
fields = one frame - (ie one complete picture), which is a complete frame
every 1/25s.

On 2008-01-05, The Simpsons wrote:

Now why would you be afraid to look, it's quite legitimate to post a link in
a newsgroup to make a point.
BTW I've said nothing about movements per second but that two interlaced
fields = one frame - (ie one complete picture), which is a complete frame
every 1/25s.



So who are you arguing against?

The point that started this mini-debate seems to be 100Hz CRTs.

They do exist. AFAIK, they just referesh the whole screen every 1/100s.
Each field would be redrawn four times, and every second refresh allternate
fields change...

--
David Taylor

Yes, but does anybody know of a decent showroom that will adjust all
it's displayed models such that they are optimized along the lines of my
post of about two days ago.

In the 'normal' showrooms nobody really knows what they're looking at,
which is fine for the average punter but for someone who is
knowledgeable enough to know what they're looking for it's a minefield.