My post was just a quick note to point out that the light received by
the eye is very different between an LCD and a CRT. I'm not surprised
it is unsatisfying.
Borrowing from the ever helpful and readily available Wikipedia
When a row line is activated, all of the column lines are connected to
a row of pixels and the correct voltage is driven onto all of the
column lines. The row line is then deactivated and the next row line
is activated. All of the row lines are activated in sequence during a
refresh operation.
At one time I think there were variations on this method of displaying
a row at a time. Some of the early LCD TVs cause motion distortion
similar to a vertically traveling camera shutter except if I remember
correctly it was imposed on blocks rather than across the whole row.
Vague memories are probably still unsatisfying but may jog someone
else's memory.
Probably Andrew's comment about the persistance of the human eye
affecting flicker is a much better directed answer to what you were
thinking about.
-jeff
On 9/27/07, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> Hmmm. I find your answer unsatisfying. Although a CRT lights each
> pixel with an electron beam sweeping across the phosphors the beam is
> moving at an extremely fast rate. So fast that it hits every single
> pixel once every 16.7 ms if the refresh rate is 60 Hz and faster than
> that if the refresh rate is higher. Obviously, the phosphors have to
> have a persistence at least as long as 16.7 ms else they'd go dark
> before the beam came around again... that awful flicker.
>
> But my question is, how can a monitor have a "response rate" (whatever
> that is) of 2 ms or 5 ms of anything less than the refresh rate? It's
> the refresh rate that's controlling how fast each pixel changes
> regardless of whether they're updated sequentially with a super fast
> beam or nearly simultaneously via addressable solid state electronics.
>
> Chuck Norcutt
>
>
>
> Jeff Keller wrote:
> > A CRT displays a single active dot of light moving across the screen.
> > It's been a very long time since I paid any attention to the inner
> > details, but a LCD displays and updates much more than a single dot at
> > any one instance. The affects of persistance are much different.
> > -jeff
> >
> > On 9/27/07, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> >> This raises a question in my mind. I know that LCD's were initally not
> >> considered good for fast moving games because of persistence. But I see
> >> some now claiming 2 ms or 5 ms response times in the specs. But a 60 Hz
> >> refresh rate is almost 17 ms. How does this work?
> >>
> >> Chuck Norcutt
> >>
> >> Ian Manners wrote:
> >>> Just to let you all know that the 'refresh rate' of LCD's is not as
> >>> important as with CRT displays.
> >>>
> >>> Why ?
> >>>
> >>> Persistance.
> >>>
> >>> CRT's have a very low persistance which is why flickering is
> >>> more evident than on LCD screens, which hold the switch
> >>> voltage a lot longer.
> >>>
> >>> Cheers
> >>> Ian Manners
> >
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