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

Wed Apr 2 08:41:17 PST 2003

Brilliant. I had no idea it was this complex. But it's great to get the  
specs.

On Wednesday, April 2, 2003, at 02:35 AM, markflo at mac.com wrote:

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