[opendtv] Re: Case for 720p60
- From: Kilroy Hughes <Kilroy.Hughes@xxxxxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 22 Apr 2010 07:46:12 +0000
Good test. The photo isn't the best test pattern however.
I'm about 3 screen heights from a 55" display, and have all 3 images nearly
full screen on their own browser tab so I can toggle between them instantly,
which highlights differences as changes in the image I am looking at. It is
more sensitive than bouncing my eyes between two images on the screen trying to
remember and identify differences. Either is valid, depending on what you want
to test; as is looking at them one at a time in random order with black in
between to see if you can consistently identify which is which.
I judge the 854 to be about half way, quality wise, between the 1920 and 704.
That is mostly on the basis of resolution in the stamens, bark texture, etc.
(the depth of field and subject show off resolution with high contrast, in
focus patterns and textures, etc.), and the jagged diagonal edges on petals.
Very subjective however.
Kilroy Hughes
-----Original Message-----
From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
Behalf Of Tom Barry
Sent: Wednesday, April 21, 2010 7:30 PM
To: opendtv@xxxxxxxxxxxxx
Subject: [opendtv] Re: Case for 720p60
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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