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Thick Face CRT's

                      Subject:                              Time:  4:38 PM
  OFFICE MEMO         Thick Face CRT's                      Date:  5/16/95

Here's a run down on our experiences with Thick Faced CRT's on MK3C's. 
1.  I have finally looked up the archived discussions that have taken place
here and have some first hand info on experiences with TE's AFD Platinum
CRT's.  We have been using TE's AFD CRT's for a few years now and have been
among the first if not the first to use the newer ones with clear glass for
increased light output, the Platinum Plus.  
2.  Some of the TE CRT's have lasted for an incredible length of time.  We
left one in for 26 months nursing it along partially out of curiosity to see
just how long it could go without failure.  It finally had to be pulled for
uncorrectable shading (burn) errors but still had good resolution and light
3.  The clear glass on these CRT's and TE's selected Phosphor recipe wind up
creating a much brighter CRT than  we were used to before.  More light creates
a quieter signal.  Measured S/N on the white chip of Negative TAF are all
around 48-50 dB for RGB (remember this is Negative on MK3C with Digi-4).  
4.  The Blue PEC had to be replaced with the same Hamamatsu type used in R and
G (HA3256) to prevent overload due to the increased light.  
5.  Phosphor grain is removed by installing an Afterglow Corrector board in
the Burn Cell Video path before the Festival input.  An uncorrected burn
Signal cannot possibly correct the textural qualities of the CRT phosphor. 
This concept is so obvious in hindsight that it's amazing no one did this many
years ago.  I think there are a few after market gadgets now directed towards
Burn Afterglow Correction. Run / Still differences can be almost eliminated by
replacing the Burn Cell Power Supply with a fixed level stable Piggyback PSU.
I digress. 
6.  Flare is reduced by the thick face. I think this is desireable,  maybe
some would disagree.  With reduced flare the color timing from scene is more
consistent and we have found it decreases  the amount of time needed to do
scene to scene color correction.  I guess alot of what we all did in the past
was not only correct the record on the film when trying to squeeze it into a
video signal parameter but also trying to cancel out flaring interaction
between objects in the scene.  Without flare you are seeing the original
record on the film more accurately.
Bye for now
Dave Corbitt/Manhattan Transfer