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Author Topic: Notes on "The Jargon of Video"  (Read 72553 times)

D Fuller

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Notes on "The Jargon of Video"
« on: July 10, 2015, 01:05:36 am »

Michael's article "Understanding the Jargon of Video" is confusing the concepts of color sampling and bit depth in video. It is a confusing subject, so let me see if I can help to clarify things a bit.

He writes,

     "An 8 bit image is described in video terms as having 4:2:0 colour sampling."

These are, in fact, two quite different concepts that affect the image in quite different ways.

Bit Depth (as most photographers will know) is the number of bits allocated to describing each pixel's color.

Color Sampling is about the resolution of the color the file contains. Color sub-sampling discards color resolution (without regard for bit depth) to save bandwidth. It happens in YUV color space before the signal is compressed into AVCHD or whatever codec is being used. A 1920x1080 4:2:0 image has 1/2 the vertical and 1/2 the horizontal color resolution. That means color is encoded at 960x540. (Luminance is encoded at 1920x1080.) When the image is decoded (whether for display, transcoding, or editing) the decoder simply up-samples the color information to 1920x1080.

Perhaps the most important consequence is that while the color can be just as rich as you'd hope, and as gradable as the bit depth allows, sub-sampled color will cause terrible problems if you try to do any compositing with it. Lack of color resolution will make any color-based keying or selection mushy. The color detail simply won't be there to give you clean, detailed edges to work with. This will not be helped by transcoding to a 4:4:4 encoded file; once resolution is gone, it's gone.

A couple of notes:
  • 4:2:2 is significantly better. It discards half of the horizontal color resolution, but keeps all of the vertical resolution.
  • All this sub-sampling happens in YUV color space (sometimes notated as YCbCr). RGB color is implicitly 4:4:4. (You can't do color sub-sampling unless you separate color from luminance.)
  • It is possible to to encode 4:2:0 color at 16 bits. (No one does it because if you are going to increase the bandwidth, you'll get more improvement by increasing the color resolution to 4:2:2 than from increasing bit depth at 4:2:0). And it is possible to encode 4:4:4 color using 8 bits (An 8-bit RGB TIFF does that.)
.

EDIT: One more note--the article states that the Sony A7s cannot output 4:2:2 video to an external recorder. It can. It outputs 8-bit, 4:2:2 video at UHD-1 resolution via it's HDMI port..
« Last Edit: July 10, 2015, 01:25:34 am by D Fuller »
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UlfKrentz

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Re: Notes on "The Jargon of Video"
« Reply #1 on: July 12, 2015, 11:08:45 am »

Thank you for this concise info  :)

D Fuller

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Re: Notes on "The Jargon of Video"
« Reply #2 on: July 12, 2015, 12:46:45 pm »

Thank you for this concise info  :)

Glad to help. I'm glad, as someone who has spent his life mostly in the motion world, to be able to contribute a bit here.

DAF
« Last Edit: July 14, 2015, 03:06:00 pm by D Fuller »
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D Fuller

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Re: Notes on "The Jargon of Video"
« Reply #3 on: July 14, 2015, 03:19:46 pm »

That's tremendous information and thank you.

One thing, as you know a lot of what we see and how happy we are with the footage is what we shoot.   The numbers don't always tell the story and sometimes a camera with great numbers just won't perform to our style one with less will rock.

Test and verify.

IMO

BC

Test and Verify. That ougta be on a T-shirt. I'd buy it.

It's absolutely true. The brew of sensor characteristics, color science, compression etc. is way more than just numbers will tell you. And when you get into post, the whole story can change again. Cameras that look pretty good on set can crack when you try to grade them. Keyers can choke on choke on footage that looks pretty good to me on the monitor. You really have to test and verify the whole signal chain if you don't want any embarrassing talks with your clients.

David
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #4 on: July 14, 2015, 05:02:24 pm »

Definatly! When resolution is gone, it's gone.

But now let me see if in practise I get the all point.

So the most important factor to take into consideration
When it comes to grading is 4.4.4 even if 8 bits.
Is that correct?

So I imagine that DNG files from BMC are actually
444 in 8bits like the tiffs? And not 10bits.

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D Fuller

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Re: Notes on "The Jargon of Video"
« Reply #5 on: July 14, 2015, 05:40:34 pm »

Definatly! When resolution is gone, it's gone.

But now let me see if in practise I get the all point.

So the most important factor to take into consideration
When it comes to grading is 4.4.4 even if 8 bits.
Is that correct?

No. When it comes to grading, bit depth is more important, especially if you have to push the image around very much. Banding will rear its head pretty quickly with 8-bit video. 4:4:4 is more important for compositing, where software has to discern edges between colors. And it's important for subjects where fine color detail is important--like some fabrics or mosaics--where low-resolution color will actually blend adjacent colors into their average. No amount of grading will get those colors back.

So I imagine that DNG files from BMC are actually
444 in 8bits like the tiffs? And not 10bits.

I don't use BMC cameras, so I've never looked into them very much, but unless BMC is doing something very odd in its processing, the DNG files ought to be 4:4:4--or to be pedantically accurate: Yes, DNG files are 4:4:4, so unless BMC takes the data through some 4:2:2 or 4:2:0 space on its way to DNG, the images they contain are 4:4:4 as well.

As I say, I'm not intimately familiar with all of the BMC cameras, but the web site says that the URSA puts out 12-bit DNG files.

DAF
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #6 on: July 14, 2015, 06:26:38 pm »

Many thanks Daf. That was very usefull and now I get it.

But then I still don't get the point of having 10 or 12bits if
We don't have 444.
It's very rare that we wouldn't need both color and compositing tasks into a Project.
So, if both parameters are not top, it's always a compromise: what we'd gain in color we'd loose in compositing
and vice versa. Before Reading your post, I thought that the most important factor was the subsampling, now I realise
that all is tremendously important.

All that then means that: no compromises or hassles on the corner.
Both 12 bit depth or more and 444 would have to be from capture,
And there we are in cine territory.

And that comes to Budget...(to change a bit no?) it seems that the best deal for money still remains Red cameras, 16bits. I can not access Arri except on rental.
Edit: the Ursa is "affordable" too, I saw the prices this morning in Madrid: 3500 euros for the Ursa mini 4k, 8000 for the Ursa, 3200 for the Studio Camera
5.000 for the JVC GY-LS300 that has a super 35mm CMOS but not that good UHD 150 Mbps 422
compared to the 14.000 for the C-500 in PL mount,  the 57.000 for the Sony FS65 (with impressive features I must say),
I think Blackmagic and Red are real bargains.
Who sells a R1? Have you seen one? Jannard was right when he claimed that the one who sell a R1 will regret it later.

Correct. BM cameras are 12bits.
« Last Edit: July 14, 2015, 08:54:54 pm by fredjeang2 »
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D Fuller

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Re: Notes on "The Jargon of Video"
« Reply #7 on: July 14, 2015, 10:27:32 pm »

Well... before I begin, I have to make a disclaimer. I love Red cameras. I owned a Red One, and a Red Epic, and I now own an Epic Dragon. So I'm not unbiased. They make beautiful pictures. Redcode is remarkable. It gives you the option of near-lossless Raw encoding that transcodes to a true 4:4:4 if you like, or, if you need a lot more record time, very good 7 or 8 to 1 compression. (That's my limit. I never go below 7:1 unless I'm shooting framerates that require higher compression to achieve the framerate.) All transcode to true 4:4:4, and 10 or 16-bit (my choice) when transcode them. It's a Raw format, so it's a very familiar concept to most photographers.

That said, i also use Arri cameras if they are right for the project, or GoPros, and I'm playing this week with a Sony A7s that I'm still not sure about. I'm open-minded, but definitely not camera-agnostic. I only have time to test and learn so many cameras to the level that I feel comfortable bringing them onto a set with a client.

Red has made a set of very good decisions about what you get to work with as a photographer. (They've also made some decisions that make me nuts, but that's a different conversation.) But you have to be willing to test and learn what the camera will deliver. The camera will not cover for you. It needs light. But if you learn it, and learn to understand light, it will give you lovely images.


Red Epic MX, Nikkor 50mm f/1.2 AIS

A Red One is heavy, but not heavier than the film cameras that I used for most of my life, and there are some advantages to a bit of mass. And it will make beautiful pictures all day long. It is a lot of camera for the money it costs these days. And both Red One and Red Epic/Scarlet are mature systems. Everything you need is available to make the cameras work as you want them to, both on set and in post. I'm not saying that's not true of the other cameras you mention; I don't know enough to speak about them. But it is true for Red.

David
« Last Edit: July 15, 2015, 06:56:04 am by D Fuller »
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #8 on: July 15, 2015, 05:59:02 am »

Wasn't Graeme Nattress one of the enginerrs behind the Redcode?
In the past he was active in this forum.
I remember some posts, although as I studdied fine arts
The engineering jargon at this level was hard for me.

I don't own a Red camera but regularly edited Red material
And I must say that I love to work with Red.
I don't understand its color science but I think that
The implementation of metadatas the way they did with
RMD is really nailed and extremely usefull in post.
Blackmagic doesn"t have a separate file like RMD and
It's a pitty.
This is where the Scratch viewer comes in action in the
Sense that it sort of become what RCX is for R3d and if I
Create a prelook, I can export color decision or Lut, reusable
Elsewhere. But
The metadatas are not separated.

As you point, Red is a lot of camera for the money.
Blackmagic interests me for budget and size reasons. They too
Deliver solid imagery for a ridiculous cost.
I'not very fan of the dng but at least we're not talking about
Those horror museum compressed codecs. It's 2k only for the pocket
But I don't care...4k is overkill for my needs.
(i saw some bmpcc 2k upsampled at 200% compared side by side
With one of those Sony or Pana 4k, and it bloody stands still).
Their proxy files is Prores 422 at 250Mbps if my memory is correct.

Cheers.
« Last Edit: July 15, 2015, 06:04:03 am by fredjeang2 »
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UlfKrentz

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Re: Notes on "The Jargon of Video"
« Reply #9 on: July 15, 2015, 03:28:34 pm »

snip
As far as 6k/8k to me that's a marketing arms race that is reminiscent of what still cameras went through, mostly with no real advantage to the content.

snip


I donīt agree.

First, this is a new sensor which is better in so many ways. I liked the MX but the Dragon is simply grown up.
Second, if you shoot 6k and edit in 2k you have so much flexibility to play around with the framing in post, itīs priceless. I wonīt ever look back.
Third, we grab still frames from the motion feed. This is not to replace our existing systems, but there are jobs that are better suited for our dragon.

Cheers,

Ulf
« Last Edit: July 15, 2015, 05:44:15 pm by UlfKrentz »
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #10 on: July 15, 2015, 03:38:56 pm »

Coot,

I agree with you that those semi-pro gear, in the end cost almost as much money to make them work properly than a Red system. And above all they are plagued with hassles in the pipeline. What you say is true for professional imagery production.

But my situation-needs is very different from yours. Coot, I'm not good at shooting, never was, never will be. This is why I never had a personal commercial webpage with

My imagery because my imagery is not at the level requiered to be sold professionaly and I'not the kind of guy to have a webpage to present my hollydays in Cancun or amateur stuff to be shared in facebook (i don't have a facebook account). Shooting is not my strengh.

I've never enjoyed that much the production and my territory basically is the editing. I hate shooting, I love cutting. So for me, a camera choice is nothing more than a tool to do my indy averageries that will never be played in any theater nor will be a source of incomes. They come from other part, and I have financial independence. I'm the guy you would hire for cutting stories, because I'm good at it, but on set I'm useless. I've always felt at home working for others, but when I got a camera in hands, I have nothing to say. If I was in your case, I would have made similar choices but what will I do with a Red camera? Amateur imagery, making-of, some erotic bondage kind of stuff. This is why a bmpcc is going to work for me in an amateur-indy reality, but if I'd need a profesional set-up, I would avoid BM for sure and go Red or Arri. I don't mess with the editorial tools, but the camera for me is like a hobby. 

Ulf, great motion works in your site. The editor is good too, understands the tempos. Congrats.
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #11 on: July 15, 2015, 03:51:54 pm »

 ;D
I just bought a bmpcc in germany

Found a strange vintage sunhood that can fit 3x3 nd filters in the US

Plus gage, plus extra batteries, plus  a viewfinder, plus plus plus...

It' gona look strange. Very Mad Max.

I tell you guys: we're soooo cool in a editorial studio without
All this artillery, cablery, rigs,
« Last Edit: July 15, 2015, 03:59:15 pm by fredjeang2 »
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UlfKrentz

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Re: Notes on "The Jargon of Video"
« Reply #12 on: July 15, 2015, 04:01:58 pm »

Thanks, Fred. I always had in mind you planned to develop your camera skills, but anyway if you found your place thatīs great. I am focussed on lighting and all that technical stuff and thatīs fine for me. @James, I see your point, and of course you know what youīre doing. I had never thought that DSMC concept could work for us but honestly youīd be surprised to see the Dragon files…

Cheers,

Ulf

fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #13 on: July 15, 2015, 07:28:10 pm »

...I always had in mind you planned to develop your camera skills...

Yes, I tried in the past, starting by assisting and because of my contacts in the art milieu I had the chance to work with a few big names and learn directly from the bests, but I totally lacked passion.
I realised that one can not become good in something if he's not driven by truth passion.

Accidentaly, I started to editing and the "bang" effect ocurred, went back to one of my first love, as when I was Young in Paris I was in // to fine arts in a cine school where I started to learn the task and always liked much much better motion imagery than stills;

and as son as I started to cut, I felt naturally "at home" and had the passion I was lacking when I was trying to learn to shoot well.
In fact, in my assistance period, I was living the glamour life, surrounded by top models, sophisticated life style, but I was "dead-alive", very superficial and not really driven by the need to express myself.
It was a sort of parenthesis where I learned more on myself, on life and psychology than imagery itself.

Beleive me, if there is not passion, it's not worth. Some people are good producers and not that much good musicians. Very few like Prince can have both. The important thing IMO is being aware where are ones strengh and wicknesses and surround one self by the correct people, the ones that are better where we're not.

You see, Thelma Schoonmaker is hired to do one task in wich she excells, she doesn't touch a color App or a camera. This is possible in the very high-end, generally most of the people are obliged to do many things for budgets reasons and it's always a compromise. But we can not be everywhere and being good at everything.
Specially, I think that the photographers are more reluctants to delegate even if they can because they are used to control almost everything in teams that are reduced. In motion imagery, things get more complicated.

Cheers.
« Last Edit: July 15, 2015, 07:44:33 pm by fredjeang2 »
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D Fuller

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Re: Notes on "The Jargon of Video"
« Reply #14 on: July 15, 2015, 07:37:54 pm »

It seems to me that there is a difference in how you need to think about motion and still images (beyond shutter speed, etc. to the kind of image that's going to be useful to you in each medum). I think switching cameras helps that. It does for me anyway. Red's latest firmware for Epic has a real still/motion mode switch that can completely change the camera's setup. I think that might help, but still--the camera with matte box and support that works for motion might still not be the right thing to help you think about the still image. I dunno.

@fred- I think the BMPCC is interesting. Almost bought one when they cut the price in half last summer, but I've sold all my S16 lenses, so in the end I passed.

@BC- I can't get excited about BMC's other offerings either. They're just too odd for me. Like shooting video with a laptop or or a brick or some other oddness. No appeal at all. I guess i want the cameras I use to be beautiful in some way. And yes, I do think the Reds are. The Epic's not a world bigger than my Contax. One of my favorite things about the camera is that I can hand hold it supported by my chest or do the "human arm gimbal" and get some very nice shots. And I can do that most all day. I'm not rugged enough any more to do that with a R1 or an Arri all day.

RE: Arri- It's easy to love Arri cameras. The pictures are pretty, and most everybody likes them. And they work like ACs have expected cameras to work since forever. (Or that's the rep anyway.) But honestly, I prefer the color I get from a Red when things click. I think it's more "complex" and I like that. (I felt the same thing about the Dalsa sensor in the P65+ compared to the Kodak P45+ when I tested them on my Contax.) It's like the individual bits of different colors that make up the overall color we percieve are more present if I want to look for them. Or maybe that's just resolution. I don't know. I just like the pictures.
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #15 on: July 15, 2015, 08:01:20 pm »

... but I've sold all my S16 lenses, so in the end I passed.

It's funny. When I was in Paris I often walked in the Boulevard Beaumarchais, wich traduced to english means "nicemarket boulevard". And nice it was indeed.
All those rusty boutiques with old S16 Angenieux, tons of Arriflex etc...
As being Paris, the old  cine-photo boutiques where looking like fashion boutiques that no one uses anymore (the Zara effect).
At that time (90's) they would almost gift you the Berthiot or Angenieux

Now kids are buying a fortune in e-bay to put their hands on those vintage stuff. It's funny how history changes.
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #16 on: July 16, 2015, 06:29:26 am »

Daf, James

I agree with you. I like the Red color.
As we're not in an Arri forum, no cultist will hang me
Reading the following:

I personaly find the Alexa material boring. Surgical.
Not saying that because of log-c but bringing the
alexa files to life require more skills. Red is organic, and IMO suits more the owner. Alexa suits more the
Rental. Maybe I over simplify but Arriraw workflow is
More aimed to collaborative.
Arri claims that all p.prod devices can handle Arriraw natively but it's far from being the reality. Or you got the debayer, or the SDK but rarely both. Everything ingests R3d but not everything handles SDK natively. (I mean
At a source setting level)

On the 6k Red, it definatly may give more room for reframing
Stabs, however the framing remains the framing and a similar zoom effect is unevitable but there is more room not to loose resolution.
Now...6k for arquitecture? I apllaude. But when human beings are involved, I think we come to the paradox that we
Have to soften the skin in post because of the detail capture
That has more to do with a dermathologist studdy than actually fashion or feature. There is a limit in wich it deshumanize.
Question: are the MUA products suitable for more than 4k ?
I beleive the answer is not yet.

Ooopppsss...in one of those cultist forum, they would have jumped om me.

« Last Edit: July 17, 2015, 08:23:58 pm by fredjeang2 »
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #17 on: July 16, 2015, 01:17:32 pm »

http://www.ducloslenses.com/collections/veydra-primes

Good lenses for BMPCC or PANASONICS

I wonder when the chinese will build a Red replica
« Last Edit: July 16, 2015, 01:34:34 pm by fredjeang2 »
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smthopr

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Re: Notes on "The Jargon of Video"
« Reply #18 on: July 16, 2015, 02:59:00 pm »

Since this has gone way off topic...

A couple months ago I used the new Panasonic Varicam.

It costs about the same as a low end Alexa.

But it records 4k 4444 prores, and can work at 5000 ISO.

I used the camera in the dark. Results were amazing!  I was putting ND.3 gels on 50w lights:)

If this camera was available where I'm filming now, I'd be using it instead of the Alexa's were filming with:)
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fredjeang2

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Re: Notes on "The Jargon of Video"
« Reply #19 on: July 16, 2015, 05:52:04 pm »

I was putting ND.3 gels on 50w lights:)
I'm going to try that with the BMPCC  ;D



Nice te see you again Bruce.

The fourth 4 , (4444) is that for the alpha channel?

If so, I imagine it is specially well designed for post FX.

Is that correct?

Is it RGB?

How heavy are the files compared to EXR or Arriraw?

I'm asking this question because I don't see-understand the importance of this in capture itself.
Would it mean that Green-screen would perfectly match the subject for ex?
why having an additional channel on capture?
« Last Edit: July 16, 2015, 06:16:44 pm by fredjeang2 »
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