THE GENERATION GAME
It doesn’t matter how much time and effort
you put into your video movies, the final production can still end up looking a
mess, if your copying procedures aren’t up to scratch
Over the past fifteen years virtually all of
the difficulties associated with editing and transferring camcorder footage to
a VHS cassette have been eliminated, except one! That’s the sometimes
catastrophic drop in quality that occurs when video material is copied from one
deck to another, using domestic analogue equipment. The good news is that one
day we’ll all be using digital camcorders and VCRs, able to make near perfect
‘clones’ of an original recording, but for the time being most of us are stuck
with analogue kit, so we’d better learn to make the most of it.
But why does this reduction in picture
quality occur, and is there anything that can be done about it? Picture quality
means different things to different people, and there’s no simple technical
definition. It’s a highly subjective matter; for some it’s the amount of fine
detail in a video image that really counts. For others vibrant, natural-looking
colours are more important. However, whilst we can all recognise quite large
deficiencies in detail and colour, the eye is actually far more sensitive to
something else, and that’s noise.
Noise is video enemy number one, and the
primary cause of the quality reduction during the copying and editing process.
Noise occurs across the frequency spectrum, but it has the most drastic impact
on the higher frequency components of a video signal, affecting both colour
fidelity and resolution. In short, the more noise there is within the limited
bandwidth of a video signal, the less room there is available for picture
The effects of noise are immediately obvious
on copies or edit masters made using low-band equipment (8mm or VHS-C to VHS).
Edges and straight lines look whiskery, colours become fuzzy and fine detail is
lost, replaced by a distinct texture or ‘grain’. Things really start to suffer
on third generation recordings -- i.e. a copy of a copy -- when noise begins to
have an impact on the recording’s synchronisation pulses. The top of the frame
can start to ‘tear’, colours become unstable, and the picture starts to look
increasingly ‘grainy’ as though it’s being viewed through a gauze screen.
Fourth generation copies are generally so unstable as to be unwatchable.
Where does all this noise come from, and what
can be done to get rid of it? Unfortunately noise is an integral component of all
analogue recording systems, and one of the main reasons there’s been such an
enthusiast shift towards digital technology in recent years; (noise is far less
significant where information is represented by numbers, rather than waveforms
of constantly varying amplitude or frequency). Noise is generated at all stages
of recording and playback, even cables and the conductive tracks on circuit
boards create noise, but the greatest contribution comes from the magnetic
tape, and electronic components in the video processing circuitry.
Clearly you can’t do much about the amount of
noise your camcorder and VCR generates internally, apart from replacing them
with better specified models, but you can make a difference by your choice of
tape and connecting leads and using good quality post production equipment.
Tape noise is by far the worst offender, so
it makes good sense to use the best high-grade, low-noise tape you can lay your
hands on; this is crucially important for the original recording! ‘Pro’ or
‘Master’ formulations cost on a little more but they can make a huge difference
to the look of final tape. A lot of tosh is spouted about connecting leads, but
the fact remains that poorly-made leads and connectors can introduce additional
noise into a system. You don’t have to spend a fortune on gold plated leads and
oxygen-free copper cables for video applications, but it makes sense to avoid
the cheapo stuff, which can quickly develop intermittent contacts through
corrosion or by being a poor fit.
Cross-format editing and copying is another
consideration. The drop in quality is most apparent on low-band edits or copies;
third generation material is usually only just watchable. Things improve
considerably with high-band (Hi8 or S-VHS-C) master recordings. The amount of
additional noise generated during copying will be about the same, but its
effects are less significant, because you’re starting out with more detail and
sharper colours. Second generation VHS recordings from a high-band master can
look as good as a 8mm or VHS-C original. By the third generation there is a
marked increase in noise, equivalent to a second generation low-band copy.
The best results are obtained by mastering on
Hi8 or S-VHS-C, editing to Super VHS VCR. Third generation VHS copies taken
from the S-VHS edit master can look almost as good as low-band originals.
The ultimate system would be all digital,
with the potential for third, fourth or fifth generation copies to be almost
indistinguishable from the original. A lot of enthusiasts and semi-pro users
are early converts to the format, and it’s the only way to go if you’re looking
for near broadcast picture quality, at a fraction of the cost of professional
equipment. Unfortunately DVC is brought down to earth with a bump as soon as
it’s transferred to analogue S-VHS or VHS, but the lower noise levels on DVC
recordings mean subsequent analogue copies will still look cleaner than
equivalent multi-generation copies of Hi8 or S-VHS-C originals.
At the moment the cheapest digital camcorders
cost £1800, and the one and only DVC VCR sells for £3,500; digital post
production equipment is still very thin on the ground, and very expensive. It’s clearly a luxury few can afford right
now, nevertheless it is a new technology and prices are coming down; we’d guess
that within a decade concerns about copy and edit quality will have been
consigned to the cutting room floor of history...
Ó R. Maybury 1997 1601