On 20/02/17 3:14, Moose wrote:
I'm not sure where the advantage lies. Although I shoot short videos of
things where a still shot doesn't show the whole aspect of the subject,
I know very little about digital video, so what I say is largely
theoretical.
If I shoot Panny 4K video, I have 3840 horizontal pixels. My current TV
is FHD, i.e. 1920 pixels wide. If I get a new, 4K TV, the horizontal
pixels match. I don't understand how compressing the width, then
uncompressing it for display, at the same resolution, can increase detail.
You are right, you will only gain better image details with anamorphic
when your monitor's resolution is higher than your source's resolution.
Anamorphic video format is very popular, the PAL DVD have resolution of
720x576 (i.e. 5:4) while the display aspect is 4:3 or 16:9.
In addition to the various problems/artifacts discussed in the Wikipedia
entry, there is inevitable loss of detail resolution. Assuming a detail
one pixel wide on the sensor with a standard lens, with a 2x optical
compression, it either disappears, or becomes 2 pixels wide, when expanded.
Yes, that's a gross simplification, but the effect is real. With fisheye
images, an app like Fisheye-Hemi can do a wonderful job of "un-fishing",
but details, especially as you move to the corners, are poorer than a
shot with a linear UWA lens. With a 20 MP sensor, for display on the web
or in a printed book, that's not a practical problem, but very obvious
pixel peeping.
Your theory about digital compression/expansion is right because the
number of pixel you have is fixed by the sensor.
In analogue world a 2x anamorphic lens might capture 2x the vertical
detail. It gives better output when decompressed with a 2x anamorphic
lens.
Likewise, with video, those effects are simply not visible to the human
eye viewing a moving picture. I remember when I was a projectionist
being amazed at the poor detail in individual frames, and the amount of
motion blur, in an apparently sharp movie.
I agree with you, on resolution aspect the visual requirement on video
is much less than still photo. But on the film movie days, film makers
usually need to shoot high ISO film, the grain and resolution of the
media is very poor when compared to the current digital media. You need
to use every mm of the media to increase the output quality.
In fact, cameras with hor. pixel counts higher than 3840 need to deal
with this issue. Panny sticks with the 1 to 1 pixel method. Looks good
on the 16 MP sensors, where the frame is only slightly narrower that a
still shot. On the 20 MP GX9, the frame coverage gets noticeably smaller
in video. If I were interested in shooting a lot of 4K video, I might be
using the 16 MP GX85.
I assume cameras with even larger sensors must do some re-sampling to
record 4K.
Yes, resampling is done on many cameras when shooting either 4k or
1080p. But still, they may not be able to use the whole sensor so some
may be cropped and not all re-samplings are the same, some give poor
video output. Checking the GX85, it gives very good 4K quality but just
so so on 1080p. Sometimes the cropping data is not easy to find, it is
very critical to video shooters.
Instead of resolution, I'm more on high frame rate. My FZ1000 gives very
sharp 4K 30p but I much prefer 60fps 1080p. I'm happy with 1080p which
save me editing time and HDD space.
C.H.Ling
Am I missing something?
Which Kay Moose
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