#Blacker Backgrounds
15 messages in this thread
How can I get really black backgrounds ? Am outputting to PAR and to
Beta Cam SP, using super black (R.4) . Still, my backgrounds are not
really black when compared to other (competing) animators' "hi end"
tapes.
This was pointed out to me by a video producer/ex-client……..
Would appreciate any suggestions—
>>Still, my backgrounds are
>>not really black when compared
>>to other (competing) animators' "hi end" tapes.
I noticed this too. Hope we get an answer. I don't think the super-black switch
is the answer!
Jim
Super black doesn't change the black level of the background at all.
It leaves the background where you set it, and then it thresholds the
values in the animation/foreground to what you've got set in your
3DS.SET file. This is so you can do a lumenance key into the
background without worrying about spillover into the foreground. Re
the actual black level… RGB000 is RGB000. Always. It don't get no
blacker than that. If you've got your background set to ANYTHING
above 000, and if you've got gamma correction ON, it would cause a
black level higher than what you're expecting (due to the gamma
curve). Is that the case?
3DS doesn't really give you "super Black" as defined in video glossary terms.
ie 0- -10 IRE black levels. In order to achieve what you want you must feed
your video signal from your frame buffer (PAR) through a processing amp and
adjust the black level (pedestal) to that level using a wave form monitor for
visual calibration. This waveform monitor is important because if you adjust
the black levels too low they may trigger the horizontal and vertical sweep at
the improper time.
See GY comments as to what 3DS really does but calls it super black. Your PAR
or frame buffer is set to always give you 7.5 IRE black no matter what you do
in software.
As to comparing to other work: Be sure you are comparing apples to apples ie
same animation, displayed on the same equipment. Others you refer to may have
just figured out how to tweak the gamma and adjust lighting better than you
have. Thgey may also have been using video equipment with better signal to
noise figures than you do. Video noise on blacks will manifest itself as white
specks causing the blacks to gray out. Signal to noise on betacam SP tape is
better than SVHS and on D-1 is non existent.
Hope this is some help.
Don Landis
>> Your PAR or frame buffer is set to always give you 7.5 IRE black no matter
what you do. <<
Hiya Don!
Actually you can get zero black out of the Targa by disabling setup and both
the Targa and AT-Vista on RGB output rely on the external encoder to provide
proper setup. Alot of VTR's however will only output black at 7.5 regardless of
how much you squash the setup on the input side, (like that technical term
"squash" <g>) unless its got a built in TBC like the AG-7750.
From the FWIW dept. 🙂
John
This is getting complicated from the original question of super black from 3DS
but the point I was making was that in order to achieve super black (of less
than 7.5 IRE) requires hardware modification on the video signal. Which
hardware you choose to do this is up to you. It could be a proc amp or your
external encoders.
>> This is getting complicated from the original thread…. <<
Sure I know, I just thought additional clarification would be helpful.
Regards,
John
Adjusting the setup on the output really does not give you negative black, as
the whole picture's black level will change. The point of negative black is to
give a larger luminance difference between the graphic and the background so
that it can be keyed. We have tried a number of ways to create this. The only
way is to push the luminance of the graphic up 10 divisions when rendering and
then render to tape, then bring the whole black setup down (from tape). I
suppose you could do this with a processor out of the PAR or other frame
buffer. The problem is that all frame buffers lock the black at 7.5.
An other way we have gotten around this is to render the animation over blue(or
other primary color) and chroma key.
Ken Adolph
Media Group
Your suggestions are indeed correct. The original intent here was to produce
blacker blacks on the whole scene. In this particular instance the intent was
not to use superblack (video def.) for keying but to use it for darkening the
blacks in the picture. The reason much video has poor quality blacks is due in
part to poor monitor quality, poor signal to noise and poor adjustment of the
pedestal.
I agree with your solution that the best way to effect a good key is to use
blue and do a chroma key. I do this here. But, this will not solve the
original problem.
I also thought that the type monitor using a black matrix grid (Hitachi) vs. a
standard shadow mask three gun tube will also yield blacker blacks in the video
output.
Blacker blacks should not have anything to do with the type of monitor you are
using. Blacks in the picture should always be 7.5 IRE on a scope. This is the
NTSC standard for broadcast and this should not be changed as this is the only
reference that we have for playback of the product. If your monitor does not
playback good blacks it is the problem with the monitor and not with the setup
level on the playback machine or computer. As long as the setup at 7.5 is
correct and the video is at 1 volt then we are all working with the same output
no matter what the monitor looks like.
Ken Adolph
Media Group
Boy, It sure does get confusing when someone takes off on a tangent in a thread
and then someone else jumps in and takes something out of context and relates
it to something else said in a different message.
To recap the topic of this thread: The original question was: How to get good
dark blacks. It was conjectured that the Super Black in 3DS might be at fault.
Both Gary Yost and I disagreed with this and I further explained that the term
super black used in 3DS is not the same definition as it is used in video post
production practices.
>>Blacker blacks should not have anything to do with the type of monitor you
are using…
FYI: I don't care how careful you are about maintaining 7.5 IRE black,
monitors DO affect the visual quality of the displayed video waveform and
Different brands of display tubes have different looks. Kind of like a
photograph printed on glossy or matte finish paper. You can talk all the
voltage levels you want but the final quality of the image is displayed on a
display monitor not a waveform monitor and this does have much to do with the
quality of black in a video signal. My only point in mentioning this is that
the original questioner was looking for a reason as to why other's animations
looked better with deeper blacks. I offered this as just one more possible
cause for the difference.
>>If your monitor does not playback good blacks it is the problem with the
monitor and not with the setup level on the playback machine or computer.
Right! that is precisely my point.
I have been keeping my eye on this thread because I've been having a related
problem with the PAR. When I send an animation from 3DS to my PAR, any black
frames are not near as black as the blank screen between each targa save. They
are more of a dark, dark reddish black. Is this normal? Will the TBC IV I'm
about to buy help this?
Thanks
Mitch
>>Will the TBC IV I'm about to buy help this?
No, ie. not directly. The TBC IV has many uses but in conjunction with the PAR
is for grabbing live video to digitize to an ani file on the PAR drive. Other
uses could indeed be to route the PAR output through it and using the TBC IV's
red and blue filters readjust the problem colors.
I'm not sure exactly what you are referring to as black screens between tga
files. I do know that the output of MY Par as measured on both WFM and VS are
as perfect as one could expect with the level of test equipment I use. I have
seen the reddish black problem before (not on PAR)and is quite common as a mis
adjusted screen drive on the red gun of the monitor. Of course if you claim
that known black test signal is OK then it may be something not right in your
PAR. I'm not that familiar with the circuitry of the PAR to comment. It would
seem that more testing is in order for you to determine the source of your
reddish blacks. The easiest thing for you to do right now is substitute
another monitor to see if the problem follows to the new monitor. Then
substitute the source of your files that cause this reddish black. I'll help
you isolate it if I can.
Is it possible to use the TBC IV proc amp controls to adjust your ani output,
or can it be used only for capture?
Mitch
Yes, you can feed any video signal, including the Par's into the TBC IV for
manipulation. I assume you want to play around with the strobe features or
filters for effects. The time base of the Par is normally OK so this would not
need correction. For ease of use I'd recommend getting the RC-2000 remote so
you won't have to use a separate computer to run the TBC IV software for this.
Without the RC-2000 doing what you want is cumbersome. Otherwise you will need
to run the Par.exe and the TBC IV software to access these features.