[Tig] DVNR settings theory and practice -- advice needed

Marc Wielage mfw
Sun Oct 7 23:39:47 BST 2001

JSnopes at aol.com commented on the TIG on 10/6/01 2:32 PM:

> ...there's a sort of grainy veiling over the
> image, mostly on scenes where higher DVNR settings (14 Y, 14 C)...
> Any other advice as to the use and overuse of DVNR?  It's a great box,
> but can be dangerous if overused.


We don't ever go that high, unless we're deliberately trying to introduce
smear and lag into the picture!

I'm reluctant to even go up to 8 on most jobs.  My advice is, don't ever,
ever go that high on DVNR noise-reduction.

You're better off, IMHO, to do two passes at a low-level of NR -- say, ANR
at 2 and CNR at 6 (in the Negative setting, which doubles the NR for peak
whites) -- and then do a second pass later on, with no ANR and with CNR set
between 4 and 6, but in the "positive" setting.  I find this is a lot more
gentle, with fewer artifacts, and the final picture doesn't look as "stepped

Noise reduction is a very, very tricky thing.  Whenever possible, I think
the best course is to avoid using it at all, except when you really have to.
In my experience, the Spirit already puts out a picture that's gonna be 4 or
5 dB quieter than the vast majority of URSAs out there (even those with
Twigi or the other ITK mods, IMHO).

Me personally, I don't think a little grain in an image -- especially from
16mm -- is that objectionable.  Otherwise, you wind up with a kind of hyped,
smoothed-over "Betacam"-looking picture, which is the last thing you want
from film.  On the other hand, we hear from the DVD compressionists that the
less grain they have to worry about dealing with, the higher bit-rate they
can use for their final master.  It's pointless to waste another .5MBPS just
trying to handle compressing tons of grain and noise.

As to aperture correction, I usually do 16mm at around 2-3, but it depends
on the shots.  For sitcoms, we'll frequently go to 4 (or above) for H&V,
particularly on wide shots, which have a tendency to look a little soft
anyway.  Close-ups can usually go down to 2 or less.  It's definitely a
scene-to-scene situation.

BTW:  I can and have gone very high on DVNR CNR settings, but only for a
single shot here and there.  *Never* the whole show.  That's the whole point
of scene-to-scene correction; DVNR is definitely a box where "one setting
does not fit all," to be sure.  You gotta keep your eye on it every second.

And with the advent of DRS, we've almost abandoned using the scratch
concealment anymore with DVNR.  Unless it's a really budget-minded client,
we just leave it turned off, assuming that the DRS guys can do a much
cleaner job with zero artifacts.

--Marc Wielage/Complete Post
  Hollywood, USA

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