[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

No Subject



At 02:02 AM 3/23/95 EST, Larry Gibbs wrote:
>Hello
>
>What is it that Improves resolution on the Rank besides the daily setup
checks
>like Gate focus/Electronic focus. 
>
>As a tube gets older and softens up what is consdered acceptable resolution
(I
>was told at one time that Rank states that 65% is acceptable)
>
>My engineer tells me that the Rank(Mk3-422) I'm on will never be as sharp as
>the Rank in the next room. Which is also Mk3-422.   Why is this?  They said
>they did a freq.sweep & put a new tube in, but still just dosn't quite get
>there. What else could we be looking at?
>Much Thanks in advance,
>Larry
>
>73132.106 at compuserve. 


Hi Larry,

This is an excellent question. It kind of opens up the old proverbial can of
worms, but here goes anyway.
There are many things that can affect resolution and sharpness: 
1.  It would be useful to know if either machine has a Festival kit, or Rank
black shading boards.  The old 658  cards are one place that I have seen
resolution diminish (there are frequency response tweaks here). 
2.  There are also frequency compensation caps in the afterglow boards and
in the color channel.  While these are set in the factory, sometimes they
get tweaked in the field, and can diminish resolution (they can also     add
lots of noise). 
3.  Is either machine enhanced? The increase contrast range and video
channel improvements are sometimes     perceived as being "sharper".
4.  Have the cellbox preamps been swept as well? (it requires an inverted
sweep). 
5.  If contours and coring are being used, are they set in the same way?
6.  The afterglow 100 lines adjustment (C7) can also influence the look (and
noise floor) of the machine. 
7.  What kind of color corrector is being used? Is it before or after
Digiscan?
8.  Some Ranks of various vintages have had inherent ground loops. Alex
Jepson is the best expert I know of in this area (and others). Solving these
can work wonders. 
9.  Sweeping the machine requires much diligence and patience.  On some
machines, a little emperical tweaking and re-sweeping and re-measurement is
needed to acheive the desired results.   Some machines are just different,
and will have a "personality" of there own. I have not seen too many
machines, though, that I would classify as totally hopeless. I'm confident
your engineers are trying hard to accomodate your wishes.  It's very
difficult to always work "miracles" in most post houses, due to the hectic
schedules  (i.e if it makes usable pictures, book it being the rule).  One
thing that can close to working miracles though is a DAV liner scan system.
It can really make the pictures "pop" if the video path is clean.

Craig


Subj:	PTR (and then some)
Date:	95-03-24 13:44:09 EST
From:	rob at xyzoom.alegria.com
To:	telecine at xyzoom.alegria.com