[MacDV] Re: pixel vs. screen aspect ratio (was: DVD player/TV crops my DVD-R)

[markflo at mac.com]

Sounds like you guys got it worked out.  Rectangular DV/DVD/D1 pixels are
taller than they are wide, which makes the picture look wider on a standard
square-pixel display like a computer monitor.

I *always* have trouble trying to explain this issue to the creatives I help
out where I work.  They've been told to design in Photoshop at 720x486 for
D1 video, which is ABSOLUTELY WRONG.  Yes, this *is* the resolution for D1
video, but since the pixels are taller than they are wide, any graphics
designed with square pixels at that resolution will look too narrow when
transferred to D1 video.  Now I tell them to use the presets in Photoshop of
720x540 for D1 or 720x534 for DV/DVD (thanks Adobe!) -- then when it goes to
the post house it will come out correctly after the vertical dimension is
squished back to 486 and displayed with the rectangular pixels of a D1 video
signal (visually squishing the width back to form a normal looking picture).

Now there's the *screen* aspect ratio issue as well...  Can you imagine the
confusion trying to explain that, yes a TV has a 4:3 screen aspect ratio,
and so does a computer monitor, but the image on the TV has a taller pixel
aspect ratio, resulting in an image with more horizontal pixels to fill the
same screen area as a 640x480 computer image...  Got all that?  Now we also
have the 16:9 screen aspect ratio, which with DV still uses the same 720x480
resolution, but the pixels are stretched horizontally instead of
vertically...  Then when a 16:9 image is played from a DV source (camera) on
a standard 4:3 TV, since the horizontal is already 720 and the image needs
to be widescreen format (16:9) the vertical dimension (480) has to be
squeezed to keep the same visual appearance...  Resulting in the letterbox
picture...  I think that makes sense...

It's late and my brain hurts.  Hope that info makes your brain hurt, too.

;-)

- Mark

On 4/1/03 10:53 PM, "Steven Rogers" <srogers1 at austin.rr.com> wrote:

> 
> On Tuesday, April 1, 2003, at 10:04 PM, Jim Asherman wrote:
> 
>> On Tuesday, April 1, 2003, at 10:40  PM, Steven Rogers wrote:
>> 
>>> On Tuesday, April 1, 2003, at 08:08 PM, Erica Sadun wrote:
>>> 
>>>> Rectangular pixels are wider, not taller.
>>> 
>>> Rectangular pixels on the TV are taller than they are wide - you can
>>> see that on some Sony TVs.  That's why an image that's ready for the
>>> TV looks wider on the computer - the TV "squishes" it up.
>> 
>> Uh I thought.. that the image looks wider on the computer because of
>> displaying the rectangular pixel perspective in a square pixel
>> environment.
> 
> Right - so long as you remember that there really isn't necessarily a
> "rectangular pixel" - it just means that the TV doesn't have the same
> number of dots per inch horizontally as it does vertically, while the
> computer monitor has 72 DPI both ways.
> 
>> Obviously the TV does not "squish" it's own native signal. It simply
>> displays the rectangular pixels correctly . It is the computer that
>> makes it look funny and has to convert the picture to square pixels in
>> order to display it properly,
> 
> Well, its a matter of perspective whether the TV squished or the
> computer is stretched. The information in the picture is the same - the
> dots are just closer together horizontally on the TV. I tend to think
> of the TV as a "squished" picture because years of working the computer
> environment makes it seem like only a loony lunkhead would make a
> display standard that has different horiz and vert resolutions . . .
> I'm sure it seemed like a good idea at the time  . . .
> 
> SR
> 
> 
> ----------
> <http://www.themacintoshguy.com/lists/MacDV.html>.
> Send a message to <MacDV-DIGEST at themacintoshguy.com> to switch to the digest
> version.
> 
> XRouter | Share your DSL or cable modem between multiple computers!
> Dr. Bott | Now $139.99      <http://www.drbott.com/prod/xrouter.html>
> 
>  Cyberian   | Support this list when you buy at Outpost.com!
>  Outpost    |         http://www.themacintoshguy.com/outpost.shtml
> 
> MacResQ Specials: LaCie SCSI CDR From $99! PowerBook 3400/200 Only $879!
> Norton AntiVirus 6 Only $19! We Stock PARTS! <http://www.macresq.com>

--  
Mark M. Florida
---------------------------
markflo at mac.com
http://markflorida.com