Sony
dropout
(c) 1998 Origin8
Video |
A single-frame dropout of 32
horizontal
pixels by 8 vertical pixels. It occurred on a Sony miniDV tape from
October
1995, shot in a VX1000. This dropout appears every time the tape is
played
in a Sony DCR-VX1000 or DHR-1000, but oddly enough it does not
appear
when the tape is played in a JVC GR-DV1u -- the only case I know of
in
which the GR-DV1u outputs a superior picture! Perhaps this
particular defect
is due to an obscure bug in the Sony codec, causing a "dropout" to
appear
where one isn't actually present? In close-up this patch is
non-uniform;
it consists of differently colored pixels, but does not appear to
replicate
any other set of pixels in the image. |
Panasonic
dropout
(c) 1998 Origin8
Video |
Another single-frame dropout. This
one,
measuring 32 horizontal by 20 vertical pixels minus a 16 x 4 chunk,
is
on a Panasonic miniDV tape shot in a VX1000; it's the worst "real"
single-frame
dropout I've seen in three years of shooting. I've had other similar
dropouts
occur in playback due to debris on the tape, but replaying the same
scene
again worked without any visible dropout. (This image is 2/3 of the
way
through a dissolve, explaining the odd, ghostlike superimposed
pictures.) |
525/59.94 banding
(c) 1998
Origin8 Video
banding during recording
(c) 1998, 2000 MeetsTheEye,
Inc.
used by
permission
|
Banding: this defect occurs when
one of
the two heads on the scanner clogs or fails. In this example, the
VTR is
starting to play through a section of damaged tape (the tape became
jammed
in a camcorder and a portion was creased and crumpled). As the tape
plays,
bands "freeze" as one of the heads ceases to reproduce clean data,
so whatever
was last placed in the frame buffer remains onscreen while the other
head
continues to play. In this example, allowing the playback to
continue usually
causes the remaining "live" bands to freeze as the most heavily
damaged
section of tape is reached; as the damaged section passes, one set
of bands
starts to show "live" data again, followed by the entire picture
going
live. Other times, head cleaning is necessary to restore a
fully-live picture.
This sample is from a 525/59.94 ("NTSC") tape, so 10 bands are
present.
In 625/50 ("PAL"), 12 bands would be seen.
I have only had this sort of noticeable banding occur once when
recording.
A head clogged momentarily, and I had five frozen bands for about
three
seconds in the middle of a take. Apparently a speck of debris
(such as
residual ME tape coating) stuck to the head, then wore away.
A single frame of this sort of banding occurs fairly often,
perhaps
as often as once every tape or two, but is hardly noticeable with
most
picture content in which there is little motion from one frame to
the next
to call attention to it. It's less of a problem with
higher-quality tapes,
and I've never seen it on DVCAM or D-7.
|
Multiple
Dropout
(c) 1998, 2000 MeetsTheEye,
Inc.
used by permission |
Other dropout: following the head
clog
described above, the frozen bands "digitally dissolved" out,
resulting
in the mosaic of dropouts as shown here during the "dissolve". At
this
point, the head clog was mild enough that some correct data were
getting
to tape; only intermittent failures were occurring as the speck of
debris
was being polished away by the passage of the tape. |