From: aq456@cleveland.Freenet.Edu (Terry Quinn)
Newsgroups: rec.video
Subject: Information on Hi8 and SVHS tape quality/dropouts
Date: 21 Nov 1992 19:05:18 GMT
Organization: Case Western Reserve University, Cleveland, Ohio (USA)
NNTP-Posting-Host: hela.ins.cwru.edu


About a week ago I spoke to one of the experts at Sony's Recording 
Media office on video tape.  I'll post some information now, even 
though I am expecting some more literature to come from them 
later.
 
My questions were centered around Hi8 metal tapes and dropout 
tendency, but covered some other areas.
 
Metal Particle tape has the metal particles attached to the 
carrier film with a binder.
 
Metal Evaporative Tape has higher signal to noise ratio, obtained 
because the particles are standing on end instead of laying down.  
It is manufactured by melting the particles into the base film, 
instead of using a binder.  The biggest problem with ME is that 
the early Hi8 transport systems were harsh on ME, and tended to 
wear off the particles.  Some of the newest systems (EVO9850 
professional system, for example, have gentler transports that are 
more compatible with ME). 
 
As the metal tapes were originally developed, they were concerned 
about accelerated aging (in the vernacular, rust) as compared to 
oxide tapes.  They have since found that they hold up better than 
standard or even "souped up" standard (like SVHS) tapes, over the 
long term.  Their tests have simulated over 10 years life. 
 
I asked if there was an explanation for why there seems to be less 
observed problems on dropouts with Hi8 than in the past (based on 
some recent posts on the net).  He said that there have been 
continuous improvements and cited two.  First, they have improved 
the tape lubricant which results in it running through the 
player/recorder mechanisms smoother and with less friction.  This 
helps to prevent the loss of metal particles, which of course 
could result in dropouts. 
 
The other thing is that they have changed the binder system (I 
assume on the MP only) going to a "cross linked" binder.  This not 
only binds the particles to the substrate, but also to other 
surrounding particles, which again reduces the chance for 
particles to come off the tape.  These types of changes were 
introduced in the professional line in July, not sure whether they 
went into the consumer line...originally there was not a 
significant difference between the consumer and professional lines 
but now they are separate. 
 
As far as the dropouts themselves, they define a dropout as a 
temporary loss of signal that exceeds 15 microseconds.  He agrees 
that the more serious ones display as a sparkle, and you would be 
unlikely to see a 15 microsecond dropout (too short).  The 
specification for initial dropout tendency (number of 15 usec 
drops per minute) is about 5 for both Hi8 and SVHS in Sony's 
professional line.  He dropped a plug, noting that 3M Hi8 tape is 
rated at 35 per minute, much worse.  These ratings are for the 
professional line.
 
He noted that even though SVHS is wider than 8 mm, it should not 
hold up any better in multipass situations (will wear out just as 
fast as Hi8).
 
He said that the Hi8 has "far superior" signal quality, that is 
very evident in multi-generation dubs.  While a reasonable dub can 
be made from Hi8 to SVHS, a second dub to SVHS will noticeably 
degrade, whereas going Hi8-->Hi8-->Hi8 will be better.
 
Care of Hi8 is the major difference that he sees, because dust 
particles will interfere more than with S-VHS.  You need to be 
more careful.  Always keep the tape in the camera, deck, or in its 
storage case (don't leave it out on the table).  Dust will be more 
of a problem.  Use clean equipment, and keep your editing area 
clean. 
 
He noted that it is adviseable to fast forward and rewide all 
archived tapes (of any type) once per year.  This retensions the 
tape and solves problems that otherwise would occur due to just 
gravity acting on the tapes.  He says that all professional 
production facilities do this at least every two years. 
 
 
-- 
                                    Terry Quinn
                                     Germantown Hills, IL
                                      tquinn@heartland.bradley.edu
                                       aq456@cleveland.freenet.edu