[opendtv] Re: Case for 720p60
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 21 Apr 2010 22:30:22 -0400
Kilroy Hughes wrote:
> [CB] If the source were HD and you were to downconvert to 720 x 480
> (anamorphic) side by side with 854 x 480 (square pixel) I think you would be
> able to see the difference. Would it be dramatic...
>
> It's significant (dramatic?) assuming you are viewing on a flat panel at
> 1920x1080 square progressive, and the 854x480 wasn't "flicker filtered"
> assuming an interlaced display.
> You pay twice subsampling and filtering to more difficult anamorphic NTSC
> sample shape, and back again, in addition to fewer samples.
> Preprocessing for CRT display is a separate issue, but in practice it tends
> to follow the sample shape.
>
> If someone is watching on an NTSC display, neither I nor they care.
>
> Kilroy Hughes
>
Well, let's let everyone be the judge, on whatever displays they have
available. I've posted 3 images on my web site. The first is a fairly
detailed 1920x1080p image. See:
<www.trbarry.com/spring_2008_1920x1080.jpg>
The second image is the result of using Irfanview to scale this down to
856x480 and then scaling back up again to 1920x1080 to match what your
1080p TV might display.
<www.trbarry.com/spring_2008_1920x1080_from_856x480.jpg>
It of course has visibly less detail than the 1080p image.
The third image is the result of scaling the first 1080p image all the
way down to 704x480 and then scaling back up again to 1920x1080. See:
<www.trbarry.com/spring_2008_1920x1080f_from_704x480.jpg>
(dunno why it says '1080f', but that's correct)
Both scaled & rescaled images lose resolution but you may or may not see
much difference between the second two. Note much of the images is
blurred due to artistic depth of field tricks but the center of the
flower is in focus, so compare detail there.
I also notice the 704 images has some jagged scaling artifacts on one
petal of the flower. That is not exactly a loss of resolution. I think
it's probably some side effect of the Irfanview Lanczos resize I used,
and probably shouldn't be there. The fool thing is maybe trying to
sharpen a bit, unintended. But it is there, and I'm too lazy to redo
this.
Anyway, apart from that, what does everyone think? Would you pay much
extra for 856 vs 704 wide?
- Tom
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