Re: Net Neutrality...

[Larry Sheldon <LarrySheldon () cox net>]

On 7/20/2014 11:08 AM, Keith Medcalf wrote:
> > An LED screen doesn't refresh the way a CRT does, right? The light
> > doesn't flash and fade, it stays constant until the next change. So
> > why would a 30 hz refresh rate make any difference at all for tasks
> > which update the screen less often than 30 times a second? Mike did
> > say he used it for doing software development.
>
> You are absolutely correct Bill, however,
>
> > Movies were shot at 24fps and TV shows at 30fps (60 interlaced), so
> > I'm not sure where the harm would be there either.
>
> In order to create a perception of movement, the images need to have "no image" between them.  24 frame progressive (such as a movie 
> theatre from real film) is usually projected as 48 frames using double shutters.  It is the "blank/dark/no image" parts between the images 
> that create the perception of movement in the brain.  For a scanning display (CRT) this is automatic -- the persistence of each display frame is 
> timed such that it only persists for one half a scan (which is why if you take a picture of a CRT displaying an image with a camera with a shutter 
> speed faster than the refresh rate, you see a rolling black bar).  The "blank/black" frames are created automatically.
>
> LCD displays, however, do not have these blank frames between the actual frames, which is why they do not create the 
> appearance of motion correctly.  Most LCD display devices, however, have a refresh rate of 60 Hz (some are higher).  
> When fed with a 30p signal, the display electronics should display blackness for every other 60p image.  If you send a 
> 60 Hz display a 60p signal, however, it will not have smooth motion.
>
> LCD's designed to display moving pictures (ie, TVs) will run at even higher refresh rates (120 Hz for example) which allows a 60p 
> display with proper blanking.  In some cases the motion vectors are calculated and only the "moving bits" are blanked (or in 
> some cases displayed as a complement image).  Devices with even higher refresh rates do even more esoteric computations to determine 
> the interstitial frames to create a proper perception of motion by the brain.
>
> Each manufacturer uses their own proprietary algorithms to determine what to actually display -- some better some worse.  Some even use a 
> "scanning backlight" which makes the LCD display "emulate" the scanning behaviour of a CRT display allowing for a 
> CRT-like creation of motion.
>
> Now, back to regularly scheduled programming....

Like TV--time for a potty break.

Really interesting read--lotta stuff I didn't know.  It is a good day.


--
Requiescas in pace o email           Two identifying characteristics
                                        of System Administrators:
Ex turpi causa non oritur actio      Infallibility, and the ability to
                                        learn from their mistakes.
                                          (Adapted from Stephen Pinker)