*Frame* Rate vs. *Refresh* Rate

[R. Mark Clayton]

Large LCD and Plasma screens use "de-interlacing" to avoid this, but this
has drawbacks because it has to either display one field for twice it's
original sample period (i.e. display a 1/50th second exposure for 1/25th
second)

So what do you think old CRT's did? Nothing of course, but they had
phosphors with a persistence of 40mS or more, so the lines drawn last time
had not faded when the alternate ones were drawn - which amount to the same
thing.

Many modern CRT sets draw the whole screen 100 times a second.

or start doing clever things like only doing this for fine details, or
guessing where the patterns of the image should be in the missing lines of
each field by examining the picture details from adjacent fields and
lines. Most large screens use the "clever" approach, but none of this
processing can be done perfectly and it tends to introduce lag, smearing
or exaggerate mpeg artefacts by freezing them on the screen for twice the
length of time they would be displayed by a CRT display which is not
de-interlaced.

Modern large screens also have to resample the whole picture from 576
lines to the 768 lines of the display which inevitably reduces the
resolution to about half of 768. This is why standard definition looks
poor on an "HD ready" screen but looks virtually the same as 768 line HD
when displayed on a CRT at 576 lines from an RGB Scart.

I think it is more to do with jpeg images, and sitting too close to the set,
so you can resolve (see individual) the pixels.

 

[Flasherly]

He still doesn't know how to make a readable post. That was just a
mess. No paragraphs, and no white space to seperate the ideas.

The whole idea of technical writing to to quickly and cleanly allow
someone to read and understand what you've written.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Your wife Linda, live New Port Richey, know Bill Blomgreen, who once
did recording work for St. Petersburg's Florida Symphony Orchestra, or
were you instrumental in first setting up University of Florida's
radio station in Tampa? The name sounds vaguely familiar.

 

[Bob Myers]

So what do you think old CRT's did? Nothing of course, but they had
phosphors with a persistence of 40mS or more, so the lines drawn last time
had not faded when the alternate ones were drawn - which amount to the
same thing.

Very few CRTs ever had persistence that long. Typical persistance
figures for TV/monitor tubes (and especially color CRTs) are on the
order of a few milliseconds (to 10% of initial brightness), tops.
Longer persistence tubes were available, of course (up to several
seconds), but were generally restricted to very specialized uses
(such as radar displays).

Bob M.

 

[Sjouke Burry]

Very few CRTs ever had persistence that long. Typical persistance
figures for TV/monitor tubes (and especially color CRTs) are on the
order of a few milliseconds (to 10% of initial brightness), tops.
Longer persistence tubes were available, of course (up to several
seconds), but were generally restricted to very specialized uses
(such as radar displays).

Bob M.

All those old IBM green phosphor monitors
were very SLOOOOW....
That was in the early XT pc era.

 

[Michael A. Terrell]

Your wife Linda, live New Port Richey, know Bill Blomgreen, who once
did recording work for St. Petersburg's Florida Symphony Orchestra, or
were you instrumental in first setting up University of Florida's
radio station in Tampa? The name sounds vaguely familiar.

I'm not married. I did work in TV Broadcast engineering in Orlando,
but not Tampa. I also built Ch 58 in Destin, Florida around 1990.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Roderick Stewart]

Don't be wicked!....he knows his stuff.

How can you tell?

 

[Ashley Booth]

All those old IBM green phosphor monitors
were very SLOOOOW....
That was in the early XT pc era.

So was the first TV I ever saw. It was in the early 50s and my father
used a radar crt (green phosphor) and a few other radar bits to make it.

 

[Bob Myers]

All those old IBM green phosphor monitors
were very SLOOOOW....
That was in the early XT pc era.

Right - that was one of the exceptions. The original IBM 8514
monitor (which is the one I believe you're thinking of) was a
fixed-frequency 1024 x 768 monitor - one of the earliest to
provide that format - but at the atrociously slow rate of
43.5 Hz, interlaced. Had it not used a long-persistence
phosphor, the slow refresh would have driven all its users
crazy in short order. Unfortunately, long-persistence phosphors
also tend to produce fairly large spot sizes, so this was a tradeoff
between trying to avoid flicker and still produce an acceptable
image at this "high resolution."

Bob M.

 

[Roderick Stewart]

So was the first TV I ever saw. It was in the early 50s and my father
used a radar crt (green phosphor) and a few other radar bits to make it.

Same here. One of our neighbours had built a huge box to receive this newfangled
kind of wireless programme with pictures. I remember the picture was very small,
and round, and green. With hindsight it was probably a VCR97 or something of
that ilk, which would have made it 6" diameter. It seemed to require a lot of
fiddling about with some brass stair-rods which had been woven into a lot of
wire netting in the attic, which meant nothing to me at the time of course, but
I think would probably have been a slot aerial, for either Sandale or Kirk
o'Shotts on Band 1, so quite big.

Rod.

 

[neon]

unless you have designed an item you will realy never know but guess. frame rate is the time that is allowed to finish a task. collect I/O data do whatever it was requiered to do in the time allowed. for instance a plane at mach 3 must complete its calculation at a fast rate otherwise splot. refresh rate is the rate at which I/O can be inputed and acted on. like your monitor how long does it take to see the changes i jusr made