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Rec. 709 vs sRGB (losing my mind!!!)

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Filip Stillerska
Rec. 709 vs sRGB (losing my mind!!!)
on Apr 13, 2018 at 11:34:37 pm

I've been trying for SOOO long to figure out when to use Rec. 709 and when to use sRGB and I'm close to giving up and pretending like these things don't exist in this world. However, I'll give it one last try.

My questions right now:
(1) To achieve more realistic blendings and motion blur I want to work in a linear color space, but this means that I have to choose between Rec. 709 and sRGB - how do I know which one to pick? (I don't have any delivery specifications - I'm creating films mostly for fun but they'll probably end up on YouTube).
(2) Why should I even work in sRGB in After Effects when Premiere and FCPX uses Rec. 709 and the final export will be made from Premiere or FCPX?
(3) Is it a bad idea to embed Rec. 709 color profile when exporting PNG-images for the web, and why?

Please keep in mind that I'm having a hard time understanding very technical explanations, so I would love to receive as simple as possible answers.

Thank you, I'm desperate for help!


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Steve Bentley
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 14, 2018 at 12:57:25 am

First, in this day and age, sRGB is a horrible color space. As I've complained before in this forum, there aren't even enough blues to do a smooth grad from one side of an HD frame to the other.
Its best to work in a color space that is at least equivalent to the one you will output to or preferably one that is more spacious.
You can always work in a "none" color space in AE (good) or the ACES space (better, but might be overkill) and choose a 16 or 32 bit composition and then choose your output file format. But it depends on the monitor you have. You don't want to building in a correction that might fight with user's monitor brand X.

I've been watching the back and forth with 709 conversation. I'm pretty sure that technically HD is 2.2 gamma not 2.4. (Even though some broadcasters are requesting 2.4). HD was supposed to fix all this but instead of one format we have, what, 19 now?

The problem these days (as in non CRT days) is that everyone has their screen tuned up to... well they aren't tuned up to anything and depending on the manufacturer, the light pack in behind can produce a different set of blacks - even a different set of blacks in different areas of the screen. And don't even get me started on OLEDs.
Its best to talk to your broadcaster or your post house and see what their specs are. I've got three networks that we send to regularly and while their specs should be identical, they aren't.

DSC labs makes some terrific HD bars files that are tuned to make a scope sit up as straight as a well trained guard dog. (And they are industry standard)
It used to be you could use a scope and rely on that. But I find now that you have to use a scope to make sure you are technically correct and accurate and then use a high quality bars file (with pluge please) and match what your monitor is putting out, by eye if you can't afford a light sensor puck.
Now you might be saying - "but we're compressing to H264". That's great for output but when creating you need more headspace to color correct or do effects with multichannel elements that need a 16 or 32 bit space to render the colors correctly (for things like depth or blur passes).

When it gets right down to it you need to make sure your screen is WYSIWYG regardless of LUT. With a pluge or elements you make on your own (with lots of detail in the toe or the shoulder of the color space curve), the difference between a 2.4 gamma and a 2.2 becomes glaringly obvious.

Remember, much of the color space talk has nothing to do with the files themselves, it more about how the file is delivered to the screen.
I personally wouldn't want to embed a color space in a file because that may alter the things you want to do with it later, or restrict what a user can see who's screen is set up for another color space.

Unfortunately color space is a deep subject (wait till you get into Logarithmic space and LUTS!) and there are so many myths out there now due to the web being a wild west of formats. And I guarantee that 90 percent of the screens used for watching youtube are not set up properly. So we are all kinda trying to craft a Faberge egg for people who don't care.

But take heart, even with my firm's OCD approach to color, color space and output formats (EXR) and the TV's I have at home (one plasma and one LCD) that I've tried very hard to tune perfectly to standards, I am always horrified when I see stuff we have created being broadcast (over air or via chromecast). It is a shadow of its former self after recompression, low compression quality or Pedestal that got added by some over eager tape jockey. You are not alone in your frustration.

So for web stuff here's what we've done.
Create some content with colors that really speak to you (so you know them when you see them) and lots of details in the 0-5 percent grays and 95 - 100 percent whites. Put that up on the web in the compression you normally would. Go to a local computer store and check out that link on lots of different machines and monitors - make sure to include some Mac retina screens. Then tweak the content or your work screen as necessary so that it looks in the store like you saw it on your screen.



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Walter Soyka
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 10:54:59 am

[Steve Bentley] "First, in this day and age, sRGB is a horrible color space. As I've complained before in this forum, there aren't even enough blues to do a smooth grad from one side of an HD frame to the other."

sRGB doesn't specify the number of blues; that's determined by the bit depth of your image and graphics system. You can't get a smooth single-color gradient over an HD frame at 8bpc in any color space.


[Steve Bentley] "You can always work in a "none" color space in AE (good) or the ACES space (better, but might be overkill) and choose a 16 or 32 bit composition and then choose your output file format. But it depends on the monitor you have. You don't want to building in a correction that might fight with user's monitor brand X."

If you set Ae's working space to None, you disable Ae's color management entirely. Whether that's good or bad depends on a number of other factors, like what your input(s) are and what your output(s) must be.

You should not choose a working space based on your monitor; in fact, the entire purpose of color management is to understand and model how different devices represent color, so that you can keep color as consistent and accurate as possible across different devices and environments.


[Steve Bentley] "Remember, much of the color space talk has nothing to do with the files themselves, it more about how the file is delivered to the screen. I personally wouldn't want to embed a color space in a file because that may alter the things you want to do with it later, or restrict what a user can see who's screen is set up for another color space."

The decisions you make with regard to color space do impact the files; they specify how the RGB values stored in the file were intended to map to actual colors. For example, if you're working in Adobe RGB and you do not embed or tag the profile in your output, other applications will assume sRGB and display the file incorrectly. If you're not working in the default space for your output (like sRGB for images, or Rec. 709 for HD video), tagging/embedding is a critical part of the color management process.


[Steve Bentley] "And I guarantee that 90 percent of the screens used for watching youtube are not set up properly. So we are all kinda trying to craft a Faberge egg for people who don't care."

Here we agree, very strongly! It is a sad state of affairs, but at least by working to the standards, we can know we've done all we can to produce good imagery.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Walter Soyka
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 10:32:11 am

[Filip Stillerska] "(1) To achieve more realistic blendings and motion blur I want to work in a linear color space, but this means that I have to choose between Rec. 709 and sRGB - how do I know which one to pick? (I don't have any delivery specifications - I'm creating films mostly for fun but they'll probably end up on YouTube)."

When in doubt, use Rec. 709. The differences between sRGB and Rec. 709 are vanishingly small, but Rec. 709 is the standard for HD video, and if you're using Premiere (which is not strictly color managed), it's what Premiere assumes.


[Filip Stillerska] "(2) Why should I even work in sRGB in After Effects when Premiere and FCPX uses Rec. 709 and the final export will be made from Premiere or FCPX?"

There's no reason to for your workflow.


[Filip Stillerska] "(3) Is it a bad idea to embed Rec. 709 color profile when exporting PNG-images for the web, and why?"

Neutral. Embedding a color profile will tell an application that's aware of color management how to treat the image, but it will not help create consistent color in unmanaged systems -- nothing will!

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Filip Stillerska
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 11:46:13 am

Thank you so much, Walter! You just answered all of my questions that I've spent weeks trying to figure out, thank you!

However, I'm curious if you think that it's better to convert to (by embedding) sRGB instead of Rec. 709 when exporting images (mostly PNG's) for the web from AE, since 99% of the image files on my computer (from the internet but also from my camera etc.) is sRGB. There's gotta be a reason that I've never seen an image file with Rec. 709 embedded...? What are your thoughts on this, should I convert to sRGB color or stick with Rec. 709 (since I'll be working in Rec. 709) when exporting final images from AE?


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Walter Soyka
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 1:45:20 pm

Yes, I think sticking with sRGB for images is a good idea. If you're using color management in Ae, you can set up an output module to handle this without touching your working space.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Steve Bentley
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 8:10:19 pm

Hey Walter,
Re the RGB blues: I just figured in this day and age the 709 variant in use would be the 10 bit one and not the 8 bit one (i've never been sure how this can be the same spec if you have both 8 and 10 bit available inside the same one). So I simply meant the 10bit 709 will always deliver more color variation in color than the 8 bit sRGB. Given the poorly lit, poorly conformed, incorrect codec (add your own malady here) that we get from film crews these days, we work in the highest bit depth/space that makes sense simply to have the head room to color correct things. (as well as take advantage of the non image channels in CGI elements). While the output we're talking about in this post is for YouTube, where sRGB would be fine, that doesn't mean the project should necessarily be in lowly sRGB 8bit. I find you end up clipping things when you start pushing the curves around.

The monitor comment of mine was, in retrospect, overly simplified - what I meant was if you have a 10 bit monitor you are missing out when in working in an 8 bit space. And conversely if you have an 8 bit monitor, don't pull your hair out when all those lovely smooth grads don't show up that are generated by your 10 bit space. (again sRGB vs the 709 10 bit variant - I'm afraid all my assumptions were based on using the 709 10 bit)

Because we can choose the kind of file we output to in AE (and therefore it's inherent bit depth and in some cases the inherent color space those formats are restricted to), are you saying that the color space in AE, which is of course defining the envelope you are working in, is also passing that color space data to the output file and affects external representation on another system, another monitor, another environment? (that truly was a question by the way not a rhetorical chest poke). In kinda the same way that photoshop can embed a profile?

You are absolutely correct when you say the sRGB and 8bit 709 are virtually interchangeable in the chroma capability. However (given the gamma questions in this and other recent posts), sRGB is spec'd at 2.2 whereas I always see 709 refereed to as 2.4. Doesn't that affect a screen delivery difference?



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Steve Bentley
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 16, 2018 at 8:18:30 pm

As a related follow up. have a look at this post:
https://forums.creativecow.net/thread/2/1128770
By setting the space to 709 isn't this user limiting what they could be doing with the footage given the space inherent in the source?



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Walter Soyka
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 17, 2018 at 3:14:46 pm

[Steve Bentley] "As a related follow up. have a look at this post:
https://forums.creativecow.net/thread/2/1128770
By setting the space to 709 isn't this user limiting what they could be doing with the footage given the space inherent in the source?"


I followed up with this on the other thread, but sort of. (See my notes above on why I think the spill suppressor is breaking in this case.) The output space is the limiting factor here.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Walter Soyka
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 17, 2018 at 3:06:49 pm

[Steve Bentley] "Re the RGB blues: I just figured in this day and age the 709 variant in use would be the 10 bit one and not the 8 bit one (i've never been sure how this can be the same spec if you have both 8 and 10 bit available inside the same one). So I simply meant the 10bit 709 will always deliver more color variation in color than the 8 bit sRGB."

sRGB and Rec. 709 have the same primaries and white point, and they define the same gamut -- you can make the same colors with both.

However, as you point out, color depth matters, a lot. Choosing to work at 16bpc or 32bpc in Ae will give you visibly better results around banding and quantization (rounding) errors -- even if you ultimately deliver in an 8bpc format.


[Steve Bentley] "Because we can choose the kind of file we output to in AE (and therefore it's inherent bit depth and in some cases the inherent color space those formats are restricted to), are you saying that the color space in AE, which is of course defining the envelope you are working in, is also passing that color space data to the output file and affects external representation on another system, another monitor, another environment? (that truly was a question by the way not a rhetorical chest poke). In kinda the same way that photoshop can embed a profile?"

There are four places where you can set a color profile in Ae's color management system: input (per footage item), the working space (per project), display (per comp), and output (per output module).

The idea is that all footage items are transformed from their input profile to the working space, all calculations are performed in the working space, and then the rendered results are transformed from the working space to the display and output spaces.

There are two main ways that these decisions affect your output:

1) If your working space is smaller than your output space, you could cause clipping in the output; the limitations of your working space would be imposed on your output space. Further, because all image tools are essentially just doing math, by changing the color space (what numbers you use to represent specific colors), you can actually change the look and feel of the tool. (This gets complicated. Theoretically, using 32bpc floating point should make any color space unbounded, but practically, once you get outside 0-1 values, the results of different tools or techniques may be unexpected.)

2) The output space itself matters. You can output in any space you like, but that doesn't guarantee that the next application in the toolchain will manage color correctly. Yes, you can embed a profile in output from Ae like Photoshop, but it's also then up to the next application to understand the profile.


[Steve Bentley] "You are absolutely correct when you say the sRGB and 8bit 709 are virtually interchangeable in the chroma capability. However (given the gamma questions in this and other recent posts), sRGB is spec'd at 2.2 whereas I always see 709 refereed to as 2.4. Doesn't that affect a screen delivery difference?"

Yes -- but also remember that sRGB is intended for display in a brighter room than Rec. 709 is.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Chris Wright
Re: Rec. 709 vs sRGB (losing my mind!!!)
on Apr 18, 2018 at 12:56:32 pm

rec. 709 doesn't have an official gamma. BT1886 made a new 2.4 standard for grading in a 2.4 environment for bluray/some broadcast stuff. srgb embedding is safer in browsers for embedding. some may take rec. 709 as 2.4 wrongly because of the missing standard. you always take a risk in embedding as rec. 709 because it could be anything.


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