#WFM V-Scope Techniques
20 messages in this thread
Michael et al.
Another question about timing systems. This one deals less with the hardware
(matter of fact this is the "you get what you see" method 🙂 and more with
technique.
What I typically do in timing a system, without access to a WFM/V-Scope is;
1) Record color bars (if available, If not I make my own) out of the switcher
to tape(s) depending on the number of sources I have. It is my opinion that
these bars will always be "good" and they will become a standard of my library
for that particular switcher.
2) Play back the bars tapes on my sources, while doing a split screen _wipe_,
not a digital effect to adjust my TBC's so that the input bars look as close as
possible to the generated bars. This is a step that should be done every time
you have new source material to work with, assuming the producer of the source
material laid down bars. I have learned that TBCs are constantly tweaked
depending on the source input, and are not "calibrated" once.
3) Enable the Digital bus of the switcher and crop the digital bus so that half
the screen is the digital bars and the other half is the analog bars from tape.
Adjust the Digital Buses controls to make the digital bars as close to the
analog bars as possible. This _should_ be a one time adjustment.
Now, the reason that I posted these three steps in timing a system is that they
seem to work for me and be a pretty consistent method for timing a system. I
realize that without a WFM/V-Scope I can never be sure that I am not "off the
chart", but as far as making what comes in look as close to what comes out I
think that this is a pretty good solution. Did I miss any steps, comments?
-John
Hi John,
GREAT POST!!!! I will start using your idea right away. It's so
simmple….I don't know why I didn't think of it myself. Normaly what I do is
adjust each source tape to the skin tones of individuals. But any of you
lurkrers must remember that to do any of this without a WFM V-Scope you MUST
have a corectly adjusted monitor.
John, what would you suggest for getting collor bars on a source tape for
those of us without a cammera that will generate them?? It seems to me that it
would be best to shoot a color bar chart since then you will be getting a
reading that is consistant with you lighting. But then again my abilitys as a
signal engeneer are not that great.
Regards,
Michael W. Towe
Falcon Video Productions
Santee Ca.
Michael,
Good question re: the in the field Color Bars. My guess is that the proper
thing to do is to get a black-box color bar generator and hook that to the
Video-In of the CamCorder, but then again, I don't know if that will reflect
the same thing that recording video through the lens/ccd will. Maybe the only
thing to do is, as you say, point the camera at a printed color-bar chart with
as good a lighting as possible, however I can see that that may be tedious and
prone to error as well.
Maybe someone else will jump in here with a better technique.
-John
Hi John,
I guess an obvious additional question would be rather a cammera with a bar
generator in it takes into acount the lighting conditions when the bars are
recorded??. Seems to me that that would be critical if you were to adjust
collor and IRE level from the bars at the head of source tape.
BEULER……BEULER……ANYONE…..ANYONE?????
Michael W. Towe
Falcon Video Productions
Santee Ca.
here, here, here from you? <grin>
-John
John, the way you time your system is just the way that I do it, with my
S-VHS/Hi-8 to MII system using the Toaster 2000 as a switcher. The thing is,
you need a good monitor to do this on, like a SONY with a Trinitron tube that
has good resolution and differentiates well between colors. I had to go out
and buy a monitor especially for this.
Regarding getting bars in the field on a camera that doesn't generate them, I
like your idea of buying a black box, like an Horita, plugging into the video
in on the camera, and recording that way. I don't see shooting a postcard of
bars as being practicle or reliable enough.
Michael,
If you are serious about video, get a bar generator somewhere. Horita sells a
combo bar/BB generator for around $290 and a full TSG unit for about $400, I
think. ('Course you could spend thousands on them – but why?)
Trying to shoot a chart onto tape for your studio standard is a way of
balancing you studio to that tape, from that camera, on that day, in that
lighting. Now, when you shoot tape with that camera, it would be a good idea
to shoot the bars for a minute or more whenever you white balance or shoot a
scene where the light changes alot. Then, assuming your studio is balanced to
a standard signal, you tune the TBC on the palybakc of that tape to give you
the bars back off tape at the levels and phase for the standard. Then if you
combine that footage with stuff shot on another camera, whose playback is also
tuned to the standard bars, then the viewer is unaware that two different
sources were used.
wmc – via Autopilot!
Wayne,
I think you were trying, but I missed it, to answer Michael and I's question
re: are color bars fed to video in on a camcorder the same (in a, er. all other
things being equal, world) as the bars that would go through a lens and CCD and
end up on tape?
-John
John, I doubt it. The camcorder resident bars are usually never in the optical
path, but generated electronically into the digital stream that is then a/d 'd
to tape. That way there is certainty that (within the limits of a/d s in the
camera) you are getting standard value bars.
A compsosite video in I think is routed direct to the record heads without
hitting the optical path either. This is, BTW generally how you "balance"
multiple cameras for a multi-cam shoot or live switched multi-cam show. Run
bars to a DA, then to each camera. Now you have one source of bars. Use the
camera timing/phase controls (assuming you have them) or the return feed proc
amp to adjust each camera's feed so they look the same (actually as close as
you can get them since they almost never look the same, cable runs and other
considerations being largely uncontrollable…). But if you short circuit the
process and record at the camera, and haven't balanced that camera's output
with say a WF/VS or by comparing to other cameras' output (and using phase and
timing to get them looking alike) then you are left to color balance in post
and you may find you don't have enough latitude on the proc amps to fix it if
the cameras are REALLY off (like each is off center in the opposite direction).
Shooting bars instead has too many varialbes that you can only get "ballpark"
control over – light temp, flux, lense coatings, age, camera white
balance/black balance accuracy, chip health, etc. And if you are doing it
outdoors its even worse.
BUT!!! If there are no internal bars for the camera, or no common bar source
you can balance to, shooting bars is the next best thing since at least there
is SOMETHING with which to tweak the TBCs in post to get as close as you can to
"same color rendition" from two different cameras. But I seriously doubt that
if you took a test signal generator's bars to the video in of the camera and
recorded it, then took a shot os a colorbar card from a test card set that they
would look the same.
Never The Same Color (NTSC) is not an undeserved moniker :^}
wmc – via Autopilot!
>>Shooting bars instead has too many varialbes that you can only get "ballpark"
control over – light temp, flux, lense coatings, age, camera white
balance/black balance accuracy, chip health, etc. And if you are doing it
outdoors its even worse.
I agree with that in the sense that machine generated bars are better for
tweaking your edit suite. But… I like to shoot location bars _in_addition_
for the reason if the something really gets screwed – bad exposure, bad color
balance, etc, haveing the location bars gives you a starting point to try to
fix the problem.
Bob
Yep – you betcha! Especially after you set-up, tune up and the "talent" shows
up with his/her own light bulbs with coloration to make them look better!
(Don't laugh – it happened once…)
wmc – via Autopilot!
Wayne,
Thanks for the information. So even though the Color-Bars are not going
through the "optical" path, you still want to adjust the values of each camera
to the same "standard". I take it that this procedure will get you as close as
possible to a well-balanced multi-camera shoot and any differences in optics
are just glat going to be there and or will have to be adjusted for in post.
-John
Assuming your white and black balances all work, and you've locked all cameras
up on the standard bars sent to each one, then most any difference of optics
etc will be lost in the differences of lighting due to angle, field of view,
etc. The bar adjustment gets it so that you don't see a red shirt become
orange when you switch cameras.
BTW, you can do this w/o a DA if you have a portable TSG. Just carry it to
each camera, feed the bars in, make the adjustments referring to the WF/VS,
then go to the next one.
wmc – via Autopilot!
Thanks for the great information, Wayne.
-John
Hi Wayne,
>> If you are serious about video, get a bar generator somewhere. <<
Well the bar generator I already have via my Video Machine. I can lay down
bars at the beginig of my tape before I go into the field. What I realy need is
a good WFM V-Scope so that I can make good use of the bars. As the old saying
goes….MO MONEY, MO MONEY, MO MONEY. :-)))
What you said about tunning to a standard set of bars makes sence.
Regards,
Michael W. Towe
Falcon Video Productions
Santee Ca.
Michael, You may want to look a TechTronix protable units. They have a little
WF/VS that was selling at NAB last year (refurm units) around $900. It a
reasterizer so you need a monitor to look at it (or I suppose you could feed it
to the in of a second camera and use th viewfinder to look at the test sig).
And for under $400 you can get some portable TSGs with bars and black.
It sound like a lot of money, but how much does a reshoot cost to mollify an
unhappy custmer? 'Course if it's just for your own use – one ALWAYS accepts
one's own rationales… :^}
wmc – via Autopilot!
Hi Wayne,
>> Michael, You may want to look a TechTronix protable units. <<
Thanks for the tip, I have one quick question on it though. Do you kow if
it accepts Y/C or just composite??
Michael W. Towe
I just got the specs on the Tek unit and it is composite only. The unit I am
leaning toward recommending is the Magni MM-400 ($1500 or so). It handles Y/C
and composite in both NTSC and PAL. If the Tek unit was Y/C the choice would
be more difficult. Magni also offers a WVM-710 with more advanced features at
a higher pricetag (just under $4000 I believe).
James Bell Jr. — Multimedia Contributor – CompuServe
The WVR-500 is not Y/C. It is, however, two channel so you could get a Y/C to
two BNC cable, run luma to one channel and chroma to the other and get your WF
from one and VS on the other channel.
However, on almost every Y/C camera/recorder/player unit I've seen that also
has composite out, there is no processing of the signal from the Y/C to the
composite output. So if you use the composite output for phase and level
adustments, your Y/C should be on target as well.
wmc – via Autopilot!
That will probably get you close enough that, unless your switcher is real
finicky, you should be able to A/B roll without too many flag edits or edit
aborts. And if you wanted to go on the cheap, you could get by that way with
just a WF to set/monitor levels.
wmc – via Autopilot!