[Tig] 5242 FILM out unstable or developing problem

Jim Houston jdhouston at earthlink.net
Mon Mar 10 01:40:55 GMT 2008


On Mar 7, 2008, at 4:57 PM, Rogério Martins de Moraes wrote:
>
> I'm Sorry, but wouldn`t this mean that the FIRST frame of image  
> would have a different density than the LAST
> one, making a density change through the whole film, rendering an  
> inaccurate transfer?

I believe there are four effects at work in the 'head-to-tail'  
recording problem.

One is the latent-image keeping stability of 5242.  All films have  
some change
in the latent-image if it is not developed right away.   A 20+ hour  
difference
between recording head and tail is responsible for between 0.01-0.03D  
of a density
difference.  The rate of change of the latent-image is effected by  
the temperature
that the film is kept at.  In the ARRI where the reels lie flat above  
the motors for
the takeup and supply, the heat from the motors (and other sources  
that heat the
magazine) cause a noticeable buildup in temperature over the course  
of a run.
This heat build-up causes the latent-image on the first frame of the  
reel
to change faster than the last recorded frame on the reel.  'Curing'  
or 'baking'
the reel from 10-20 hours will let the latent image of the last frame  
change
enough that it becomes closer to the change of the first frame  
(though they
can never be equalized,  it is like a dog's tail chasing his head.)

Another possible effect is the change in sensitivity of the film as  
it is heated.
This is a small effect and may be responsible for 0.01-0.2D between head
and tail.

Third, the ARRILASER has a feedback circuit that is intended to  
stabilize
the laser power to a consistent level, however this circuit can  
sometimes
allow 'quantized power' changes over time that are usually
at 0.01D or less for a particular frame.
  (This is only a problem if you are recording to a high-gamma film  
stock or print film)

Last, it is certainly possible that the Lab is introducing some drift  
from head to
tail of the roll.  This happens all the time and is usually within a  
certain lab standard tolerance
of under a single 'printer light' change.  No chemistry is perfect  
and depletion and
an incorrect replenishment rate can effect density deltas between  
head and tails.
If the total difference is greater than about 0.07D in any color, you  
are likely looking
at some visible differences.    You could test the labs developing by  
flashing a
2000' roll and then developing it immediately.  This would catch some  
issues
in the developer if it isn't pretty close (it is rarely perfect).

This difference in densities is one of the main reasons why 'one- 
light' prints from
DIs are actually somewhat rare.


> There's a way to correct
> this difference, if it exists? Never worked with ARRI laser, but  
> curious.

The change isn't consistent or repeatable enough to have an  
algorithmic solution.
There have been attempts to slowly delta in predicted changes over  
the course of a recording
run, and it can help if done subtly (and best only on scene splits).   
But it is easy to over-correct
some shots and not effect others enough.

Jim H.
PostworksLA





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