FS7: "REC709 is an HD gamma".

JPNola

JPNola

Veteran
excuse the grab-bag of topics and questions:


* Recently an Editor said to me that "REC709 is an HD gamma. REC 2020 is a 4K gamma." To what extent is that true? If I am not mistaken it is possible on the fs7 to shoot in 4K with a REC709 gamma. Not that such would make it untrue that REC709 is an "HD gamma".


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* I recently received the following camera specs from a client:

"Format: Sony Fs7
Aspect Ratio: 16x9
Frame Rate: 23.98
Codec: 4K XAVC
LUT: SLOG3"

Needless to say, the specs left me confused. Is s-Log in any way, shape, or form a "LUT"?

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Yesterday I shot in Cine EI, SLog3 with a 709 LUT on the VF. But the display appearing with the histogram said "slog3". I had a recollection that in the past the display appearing with the video signal monitor matched the LUT you were employing in the VF and not the color space you were shooting. Does the indicator on the video signal monitor ever display the LUT type? Or does it always display the type of color space in which you are recording? If it is the latter, that seems rather redundant since it is already displayed on the screen along with the frame rate ( be it that you have that display function enabled ).

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Of all the times that I have asked for camera specs for a shoot with the fs7, I don't think I have once received specs that included everything I needed to know. I always end up having to make further request for specs or just use my best judgement after the client has no answer or just doesn't understand what is being requested.

Me: "What codec would you like me to use?"

Client: "Oh, we want Slog. We want 4K with the SLog codec."


Because all the hip people are shooting in the SLog codec.


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While I like all the new tools for shooting video, there are times when I miss the simplicity of the "old days". All the client needed to tell you was the frame rate and whether they wanted drop or non-drop timecode. That, the clients could handle. Well, most times, that is.
 
Discussion/debate around REC709/2020 sort of depends on how you are referring to them ie. as standards or color spaces. Therein lies the confusion. We know that there are plenty of different gammas that can fit into REC709 space (for example on our Sony camera's any gamma from the HG's to slog are stored in the REC709 standard) but from a specifications and standards point of view, I guess yes the editor is correct in that REC709 is more of a HDTV spec whereas 2020 is more defined around UHD.

If your client says they want LUT slog3 they mean they don't want any LUT on the footage and likely only want straight up slog3. It's wrong to call slog3 a LUT, slog3 is a gamma curve.

Clients won't really know "codecs" all of the time. I usually approach it by asking what quality / robustness of recording they want and give them a run down of options. With the F55 it's usually I'm offering XAVC or RAW. I'll also find out if they need ProRes instead and if so then I show them how to transcode it or transcode it for them.
 
I think its a bit nuts to say REC 709 is an HD gamma... all are TV,s are 709.. Ive shot tons of stuff in 4K .. for TV.. so its 709 at the end of the day.. even if shot with the Slog codec :).. sort of a weird thing for an editor to say..?
 
I don't think it is such a strange comment, Rec2020 or actually Rec2100 (same color space but with HDR) will become the preferred color space for 4K.
 
HDTV and 4K are about the number of pixels.

REC709 and REC2020 are about the brightness of the pixels.

In theory, they are independent. You could have 4K in REC709, and 2K in REC2020. You could have 320x240 resolution in REC2020. You could have 12K in REC709.

In practice, these specs can come bundled. Manufacturers announce televisions that have 8K at the same time they also change the color from REC709 to REC2020. So I guess that's all your editor could truly say: "REC2020 generally goes along with 4K, at least nowadays." For your sanity, just take it to mean, "I want you to shoot this in 4K, and I want you to shoot it in REC2020" (or whatever).

Is s-Log in any way, shape, or form a "LUT"?
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Yes. Just not a very pretty one.

A look-up table (LUT) is a table where you look up things (Is there any other kind?). In our case, it translates one number to another number. "The brightness level of pixel A1 is 2. Oh yeah? Well, we're going to change it to 4. All pixels that were 2 are now 4. Next pixel..." In the case of SLOG I would still consider it a LUT because it is translating the incoming photons to numbers (in the case of 10-bit, for example, it is a number between 1 and 2^10, that is a number between 1 and 1,024, well actually between 0 and 1,023. That is all. "This photodiode has 43 photons trapped inside it. Let's translate that to the number 12. Next pixel...") Your TV then translates "12" to a certain brightness level in that particular pixel when it's playing it back.
 
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The Client hasn't changed since the "old days" he remains as clueless as he was back then only the amount of things that there is to know has grown.
 
icarusfilm said:
The Client hasn't changed since the "old days" he remains as clueless as he was back then only the amount of things that there is to know has grown.
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Spot on Icarusfilm. The names change but that's about it... As a shooter my knowledge continues to grow. I wish rates would too.
 
When broadcast switched to HD, they changed the broadcast standards from 601 to 709. This just remapped certain Luma and color points but wasn't that big of a change. I think there was also a wider gamut (color space), but not sure exactly how much or how. The most notable difference is that broadcast standards known as rec709 was tailored to 16:9 aspect ratio, square pixels and now, if you play rec601 SD footage on a rec709 calibrated monitor, it displays skintones a bit more magenta...but lots of people don't even notice. However, now with the introduction of 4K, the broadcast recommendations are being improved to a much wider color space, and more stops of dynamic range (HDR).

You can still take your 4K footage that was recorded in S-Gammut and process it in a rec709 post pipeline, you simply have to take the steps you take any time you are going from one colorspace to the next. Alternatively, you can record 4K footage and record it in rec709 in camera. The broadcast recommendation just makes sure color are predictable between the broadcaster and the TVs and monitors within a given market.

Currently I believe there are 4K displays that are still only rec709 compatible. This is because broadcasters are still employing rec709 pipeline. I do believe that some high-end 4K and 2K monitors, however, are already capable of rec2020. I could be wrong about this, though. If not completely, than almost completely.

While rec709 and rec2020 do have standard gamma curves that render naturalistic mapping of the luminance from black to white for displays, it can be misleading to speak about rec709 or rec2020 as a gamma. They are complex broadcast standards that specify many things other than gamma curve. Plus, even when working with a rec709 colorspace, one can tweak the gamma curve in the post pipeline so that luminance is not displayed strictly in the rec709 specified way (although this can get tricky to talk about since in post we are always tweaking the luminance curve in the RGB and Y channels).

So for example, you can record in rec709 gamut, and s-log gamma curve...regardless of resolution.
It's all pretty confusing, since the terms sound the same, and can be quite esoteric. Gamut is colorspace, gamma is luminance curve, and broadcast recommendations comprise both and then some! Haha

In short, Rec709 is broadcast standard comprising of a color range/space, a gamma curve to map luminance levels within a given luminance limit or dynamic range. The purpose is so that video can be displayed predictably across televisions and monitors all over the world. While rec709 is a broadcast standard that was created with the advent of HD, it is not resolution specific. Also, when you shoot rec709 in your camera, no matter what resolution you shoot, all you are saying is that your camera is limiting the colors and mapping primaries in a way that is limited to and compatible with rec709 broadcast standard. This means that you are setting the gamut of your recorded footage as already converted and compatible to the rec709 standard. However, the gamma curve can be any flavor of log, hypergamma, or any other gamma curve to distribute the dynamic range of the camera in any way you choose, even if it differs from the rec709 standard gamma curve, even if you are recording in rec709 gamut, no matter what resolution. So you can shoot and display 4k in rec709, and HD in rec2020...or vice versa.

As far as LUT, well it doesn't matter as much what your client thinks it means, as long as you understand what they are asking for. In this case, they are just saying, hey, I want slog3. :)
 
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Cary Knoop said:
I don't think it is such a strange comment, Rec2020 or actually Rec2100 (same color space but with HDR) will become the preferred color space for 4K.
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But empircally the statement "Rec709 is an HD gamma.." its totally incorrect.. . apart from that its fine.. :)..
 
REC709 and REC2020 are referring to the dynamic range you are able to display. HD and 4K are pixel resolutions. In times of technical progress both stepped ahead but aren't connected. The statement "REC709 is an HD gamma. REC 2020 is a 4K gamma." seems to be a phrase he picked up and he his spouting out to impress.

When I stepped into a new business like 15yrs ago digital still photography or 8yrs ago video shooting / filmmaking I met people who seemed to be experienced and where willing to share the experience. I was new and not so experienced there therefore I mostly nodded reverentially. Later I found out that a lot of these statements where just bs and the expertise wasn't that great as I expected. I still wonder how much smattering flows around.
Unbeaten until today: Q: "in what pixel size you need the files?" A: "300dpi. We always need 300dpi."
 
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I really, really, really hope no one comes to this thread to educate themselves on what Rec.709, LUTs or HDR is.

Factual information like this is ill suited to be studied on forums where people "pitch in" with their personal take on the matter. Just go to Wikipedia or any official white paper on the matter. And if you have a problem with Wikipedia not being accurate due to an article you once read, then update the current one on the topic—if you're expert level.
 
AndreeOnline said:
I really, really, really hope no one comes to this thread to educate themselves on what Rec.709, LUTs or HDR is.

Factual information like this is ill suited to be studied on forums where people "pitch in" with their personal take on the matter. Just go to Wikipedia or any official white paper on the matter. And if you have a problem with Wikipedia not being accurate due to an article you once read, then update the current one on the topic—if you're expert level.
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Yeah, some dicey info on this thread. Not all bad, though :)
 
abreu-canedo said:
Yeah, some dicey info on this thread. Not all bad, though :)
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You're right. There are a couple of accurate bits and pieces in there, but the problem is everything else that is mixed in—especially for someone who isn't sure and is looking for information.

And then there's the problem of partial information, or stuff that is "true" in "a certain light"...

Some topics are simply multi facetted and it's a huge task to summarise them in a post. And even if you do a stellar job, it's easy for someone else to point out the stuff that is inevitably missing (since it was a summary), which makes the well intended effort a frustrating experience.
 
I think we as camera people need to do what the client requests, unless there is a glaring contradiction or they are asking for something we know will cause them problems in the edit. If the client specifies...

"Format: Sony Fs7
Aspect Ratio: 16x9
Frame Rate: 23.98
Codec: 4K XAVC
LUT: SLOG3"

than you don't burn in a Look, you record S-Log 3 and the only question I'd have shooting with the FS7 would be S-Log 3 or S-Log 3 Cine.
 
gkantziper said:
I think we as camera people need to do what the client requests, unless there is a glaring contradiction or they are asking for something we know will cause them problems in the edit. If the client specifies...

"Format: Sony Fs7
Aspect Ratio: 16x9
Frame Rate: 23.98
Codec: 4K XAVC
LUT: SLOG3"

than you don't burn in a Look, you record S-Log 3 and the only question I'd have shooting with the FS7 would be S-Log 3 or S-Log 3 Cine.
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Yeah. There’s nothing there I don’t understand. It’s not the client’s job to understand how to communicate with us on what should be a very highly specialized technical level. It is OUR job, however, to effectively understand what the client is trying to tell us and that just means good communication, trust, and sometimes a bit of hand-holding. I’m surprised the OP managed to get the above level of information from them.
 
JRJphoto said:
Yeah. There’s nothing there I don’t understand. It’s not the client’s job to understand how to communicate with us on what should be a very highly specialized technical level. It is OUR job, however, to effectively understand what the client is trying to tell us and that just means good communication, trust, and sometimes a bit of hand-holding. I’m surprised the OP managed to get the above level of information from them.
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I disagree. How are we supposed to know the shooting specs if someone on the client side(whether that be the person that contacts you initially, their editor, producer or someone) does not tell us? Or does not point us in the right direction of whom to ask. Communication is a two-way street.

And just to be picky and pedantic, 'Format' is not the camera model number. I would, however, allow the substitution of 'Format' for 'CODEC'.
 
In my experience, the first question to ask is "Who's the editor and what's their cell phone number?" I've gotten some 'spec sheets' from companies for shoots that make sense, but just as often they haven't been updated or seem totally illogical. Once I even followed a spec sheet precisely - only to get a phone call later from the editor telling me the edit system couldn't accommodate the codec production had specified on the spec sheet. That of course made it MY problem, not theirs... Now I talk to the editor first.
 
"Yeah. There’s nothing there I don’t understand. It’s not the client’s job to understand how to communicate with us on what should be a very highly specialized technical level."

Really hope your being sarcastic here. :)... its not very highly specialized on a tech level.. its the camera specs.. its the very basic needs for the shoot.. and yes the client does need to communicate or find someone who can.. thats is their job .. and it aint that hard..
 
I always try to get a direct line to Post but it is often difficult to get that line of communication going as producers often suffer from a severe form of Dunning–Kruger effect that convinces them that everything should go through them. Every production where I could strategize with the post people prior to shooting has always been the most smooth in execution.


OnSet said:
In my experience, the first question to ask is "Who's the editor and what's their cell phone number?" I've gotten some 'spec sheets' from companies for shoots that make sense, but just as often they haven't been updated or seem totally illogical. Once I even followed a spec sheet precisely - only to get a phone call later from the editor telling me the edit system couldn't accommodate the codec production had specified on the spec sheet. That of course made it MY problem, not theirs... Now I talk to the editor first.
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