Fair enough. You would have to resample/interpolate between your
nonsquare pixels to display them on a square-pixel SD monitor, which
would be less pristine than if you had a pixel-to-pixel mapping from
input to output.
By the same token, if you were trying to display your square pixel
sensor image on a non-square device like an analog TV (this is SD we're
talking about, after all), you would have the same issue, but in
addition you would need to add some horizontal resolution -- adding a
horizontal blowup, essentially.
Since we're introducing the complication of the display, in a real-world
scenario, your SD image is likely to get blown-up for viewing on an HD
TV. In that case, both images need to be blown up and interpolated --
but now the extra rez in the non-square image means you can use a
smaller horizontal scale factor to fill your 1920x1080 square pixel
screen. Which do you think would look better in this scenario?
Cheers,
--Michael
On 12-01-26 7:49 AM, Terence Curren wrote:
>
> You are assuming the monitor and the sensor are the same. In other
> words, a 4:3 computer monitor with square pixels is going to show that
> 1" line that was shot non square as shorter than 1". What if the
> sensor shoots square, and your monitor is square, are you now getting
> less information than the stretched pixel?
>
> --- In Avid-L2@yahoogroups.com <mailto:Avid-L2%40yahoogroups.com>,
> Michael Brockington <brocking@...> wrote:
> >
> > Respectfully, Terry, I have to disagree.
> >
> > When sampling non-square pixels for NTSC, it implies you have a higher
> > sampling frequency in the horizontal direction than if you were
> sampling
> > square pixels.
> >
> > Imagine you have a sensor that is 1 inch wide. You sample it one line
> > at a time from top to bottom, to get your 480 lines -- that part
> doesn't
> > change between square and non-square pixels. For each individual line,
> > if you take 720 samples, each sample will be 1/720th of an inch apart
> > horizontally. If you take 640 samples, they will be more widely spaced
> > -- each 1/640th of an inch apart -- you will be sampling that line of
> > the sensor at a lower resolution horizontally.
> >
> > So in this example, which I have made up to make the math easy, the
> > following is true:
> >
> > In the case of square pixels, the distance between horizontal
> > samples is identical to the distance between vertical lines -
> 1/640th of
> > an inch in both directions.
> >
> > In the case of non-square pixels, the distance between samples will
> > be 1/720th horizontally, but 1/640th between vertical lines.
> >
> > Regards,
> > --Michael
> >
> > On 12-01-25 9:01 PM, Terence Curren wrote:
> > >
> > > You folks don't seem to grok square pixels vs. non square pixels.
> > >
> > > http://en.wikipedia.org/wiki/Pixel_aspect_ratio
> > >
> > > And here you can see the ATSC standards for SD, both square and non
> > > square:
> > >
> > > http://en.wikipedia.org/wiki/ATSC_standards
> > >
> > > --- In Avid-L2@yahoogroups.com <mailto:Avid-L2%40yahoogroups.com>
> <mailto:Avid-L2%40yahoogroups.com>,
> > > Michael Brockington <brocking@> wrote:
> > > >
> > > > I'm with Steve on this one.
> > > >
> > > > 720x486 = 349,920 pixels
> > > > 640x480 = 307,200 pixels
> > > >
> > > > They might both be SD technically, but the first one has about
> 14% more
> > > > resolution.
> > > >
> > > > Cheers,
> > > > --Michael
> > > >
> > > > On 12-01-25 3:14 PM, Mark Spano wrote:
> > > > >
> > > > > Steve,
> > > > >
> > > > > 480 lines of resolution is SD. The math there is that .9 ratio
> > > times 720
> > > > > equals 648 but that is representative over 486 lines. 640 is the
> > > best math
> > > > > for 4x3 to get 480. (640 *3 / 4 = 480). And we're talking
> about square
> > > > > pixels, so that math works out perfectly.
> > > > >
> > > > > The artful look of the square is the best reason I've ever
> heard why
> > > > > anyone
> > > > > would shoot this way. But possibly the fear of downconversion
> > > softness is
> > > > > why they shot SD for an SD spot.
> > > > >
> > > > > good luck...
> > > > > -Mark
> > > > >
> > > > > On Wed, Jan 25, 2012 at 6:08 PM, Steve Hullfish
> > > > > <steve4lists@ <mailto:steve4lists%40veralith.com>>wrote:
> > > > >
> > > > > > I don't buy that. I mean I know it's CLOSE to real SD, but...
> > > > > >
> > > > > > The difference between square pixels and 601 pixels is .9
> right?
> > > The
> > > > > math
> > > > > > (720x.9) works out to slighly more than 640. And 480 is a
> little
> > > shy
> > > > > of 486.
> > > > > >
> > > > > > Avid used to claim 640x 480 was broadcast SD, but it's really
> > > 720x486.
> > > > > > With 720x480 being DV and DVD.
> > > > > >
> > > > > > So it's CLOSE to SD, but I say it's NOT SD. The bigger question
> > > is WHY
> > > > > > shoot 4:3 SD when you have a 16:9 camera? For the artful
> look of the
> > > > > > square? :-)
> > > > > >
> > > > > > Steve Hullfish
> > > > > > contributor: www.provideocoalition.com
> > > > > > author: "The Art and Technique of Digital Color Correction"
> > > > > >
> > > > > > On Jan 25, 2012, at 4:38 PM, Terence Curren wrote:
> > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --- In Avid-L2@yahoogroups.com
> <mailto:Avid-L2%40yahoogroups.com>
> > > <mailto:Avid-L2%40yahoogroups.com> <mailto:Avid-L2%40yahoogroups.com>,
> > > > > Steve Hullfish <steve4lists@> wrote:
> > > > > > >
> > > > > > > <<it has a 640x480 setting. So that's actually LESS than SD.>>
> > > > > > >
> > > > > > > Not actually. If it's square pixels that is SD.
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > [Non-text portions of this message have been removed]
> > > > > >
> > > > > >
> > > > > >
> > > > > > ------------------------------------
> > > > > >
> > > > > > Search the official Complete Avid-L archives at:
> > > > > > http://archives.bengrosser.com/avid/
> > > > > > Yahoo! Groups Links
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > > >
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> > >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
[Non-text portions of this message have been removed]
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