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Everything Nathan Knows About Color Pt 1 - Transfer Functions (Patreon)

Published:
2022-01-01 23:48:22
Imported:
2026-06
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Content

Guest video by Nathan! :DColor is a confusing thing. As I said in the color tools video, basically everything I know about light and rendering (color/eyesight/bit-depth/transfer functions/path tracers/etc) comes from Nathan sitting down with a sketchbook and explaining it to me.  Which is why I'm really excited to post this video- the first in a series as he goes through how computers represent light/color, and how that affects you as an artist.  And having this information floating around in your head means a lot of things in the world just make more intuitive sense- jpgs and compression and the way we perceive light and send images through the air and all that fun stuff.I hope you enjoy it as much as I did! 

Files

Everything Nathan Knows About Color Part 1 - Transfer Functions

Guest video by Nathan! Color is a confusing thing. As I said in the color tools video, basically everything I know about light and rendering (color/eyesight/bit-depth/transfer functions/path tracers/etc) comes from Nathan sitting down with a sketchbook and explaining it to me. Which is why I'm really excited to post this video- the first in a series as he goes through how computers represent light/color, and how that affects you as an artist. And having this information floating around in your head means a lot of things just make more intuitive sense- jpgs and compression and the way we perceive light and send images through the air and all that fun stuff.

Comments

NickTricc

2 years late, but F3 - bake action (object -> animation - bake action) will do the trick!

csmiles

Is there a part 2 and 3 available now? :) This is great info.

Victor Fredin

Man this is exciting stuff, have only watched a few minutes and I'm loving it.

Sam Goldwater

*stops everything* Seeya later everyone, Nathan's colour tutorial is out

Chris Alldridge

I’m so glad that this is a series; it’s absolutely fantastic!

Carter Burr-Kirven

Super exciting to see you guys using your reach and influence to try to raise the level of knowledge about this stuff! I wonder if you might want to be careful about using the phrase "linear color" when you're still just talking about gamma and transfer functions, and intending to get to gamuts later? Especially with the widespread misunderstandings about what "linear" actually means—e.g. "oh, we don't need to use ACES, we render in linear,"—"I'm trying to convert my footage in Resolve, but I can't find linear in the list of color spaces"—etc

BC Holmes

This was excellent. The rationale for colour profiles has always eluded me, and your explanation was just perfect.

Raf Stahelin

This is what I’ve been waiting for in thr Blender metaverse

Nathan Vegdahl

That's a fair point! But please keep in mind that this is the first video in what will be a larger series. My intention here is to focus the first two (or maybe three--I'm considering covering dynamic range earlier as well) videos on just issues related to luminance, since that's generally more important to get right (with the human visual system being more sensitive to luminance than chrominance, and all that). Covering gamuts etc. properly also requires laying a lot more groundwork about how the human eye, camera sensors, etc. work before you get to the "useful" stuff, and I wanted to start off with something that is immediately and practically useful, to hook people a little bit better. But absolutely, I will be making a very clear distinction between whether your color representation is linear or not, and what gamut your color representation is using.

Carter Burr-Kirven

Yeah, it's really a nonissue in the context of the full video, and especially three more videos down the line where everyone will be totally on board with the specifics! I just worry about the lizard brain latching onto particular phrases and coming away with unquestioned assumptions or heuristics, you know. The video's great, looking forward to the rest! I love that you spent some solid time on displays and mismatched functions, I've met so many people under the impression that linear data "looks dark"

Virtual Production Partners

Really looking forward to the Scene Referred values conversation. I’ve been trying to get a reliable way to emulate a light meter in blender that is transferable to the real world. Thanks for this and all of the tools!

Blake Rizzo

Thanks so much for this Nathan! So excited for the full series!

Vlad Tkach

I just want to mention that subcscription to your Patreon is definitely the best investment of money to value I have. Superb! Thank you so much!

Lumberhacker

Wonderful explanation. Thank you.

Jeziah Alvarez

This is straight up no joke. I've learned literally SO much in such a short amount of time

Justin

great content! unrelated but is nathan related to Ian? you have a lot of similar mannerisms and speech characteristics

cdilla

Thank you for this. Very educational and useful stuff well presented.

Nathan Vegdahl

Nope, not related! But I *am* trying to steal his identity (don't tell him!).

Nathan Vegdahl

I'm glad it was helpful! One of the things I super glossed over in this video is *why* there's more than just one transfer function out there. With the explanation I gave, you'd think there would just be one ideal curve that perfectly matches human's perception of luminance. But there are actually other factors involved as well. As just one example, there are different considerations for a transfer function intended for footage that will later be graded vs a transfer function intended for final delivery of a completed film. And that's when you start getting into weird acronyms like OETF and EOTF. Throw in a good bit of historical baggage on top of all that, plus companies constantly tweaking things, and that's how you get a truck load of transfer functions, ha ha.

Samuel Jerome Mason

Have either of you looked at the display prep demo / Steve Yedlin's work in color? Following his argument any high quality source can be transformed to match another camera / source look, this is through (i think) 3d tetrahedral color transformations and then in the case of film emulation, grain / halation, gate weave. One exciting use is to make digital look effectively identical to film. But also to things like make black magic, or sony a7 footage look like alexa footage etc. https://www.yedlin.net/DisplayPrepDemo/DispPrepDemoFollowup.html is any of this of interest in working in blender? Would be exciting to take various sources (3d render, camera footage such as sony s log) and using 3D display prep, emulating a particular film stock etc? just ideas. Also, folks have started reconstructing Yedlins tools in various open source tools. Blinkscript for nuke but also matlab etc. https://www.juanjosalazar.com/color-science https://www.reddit.com/r/colorists/comments/lku2t2/tetrahedral_interpolation_dctls/

Nathan Vegdahl (edited)

Comment edits

2026-09-20 10:00 > Following his argument any high quality source can be transformed to match another camera / source look This is not true, but the reason it's not true isn't easy to grasp without first understanding the relationship between color vision (both human and camera) and light spectra. This is one of the things I'll be covering later in the color series, and is actually (IMO) one of the most fascinating and fun things about color science. Having said that, you certainly can transform colors to *artistically feel* like they were shot with other devices. So from that perspective he's correct. But you can't do it in an objectively, quantitatively color-accurate way. It's one of the reasons why even with a proper color pipeline, footage from different cameras never *quite* match without manual case-by-case human intervention and/or involving things like color checkers.
2022-01-02 18:42 > Following his argument any high quality source can be transformed to match another camera / source look This is not true, but the reason it's not true isn't easy to grasp without first understanding the relationship between color vision (both human and camera) and light spectra. This is one of the things I'll be covering later in the color series, and is actually (IMO) one of the most fascinating and fun things about color science. Having said that, you certainly can transform colors to *artistically feel* like they were shot with other devices. So from that perspective he's correct. But you can't do it in an objectively, quantitatively color-accurate way. It's one of the reasons why even with a proper color pipeline, footage from different cameras never *quite* match without manual case-by-case human intervention and/or involving things like color checkers.

> Following his argument any high quality source can be transformed to match another camera / source look This is not true, but the reason it's not true isn't easy to grasp without first understanding the relationship between color vision (both human and camera) and light spectra. This is one of the things I'll be covering later in the color series, and is actually (IMO) one of the most fascinating and fun things about color science. Having said that, you certainly can transform colors to *artistically feel* like they were shot with other devices. So from that perspective he's correct. But you can't do it in an objectively, quantitatively color-accurate way. It's one of the reasons why even with a proper color pipeline, footage from different cameras never *quite* match without manual case-by-case human intervention and/or involving things like color checkers.

Manuel Grewer

Great stuff! I'm a Physicist and I love spectra and power distributions. Makes everything so much more complex :D

Samuel Jerome Mason

Excited to hear about light spectra! Is the tetrahedral interpolation stuff new? Or is this just a visualization of shifting hues and values. Also apologies if I'm going off-topic here!

Abraham Mast

Thank you Nathan! Excited for the next videos. Supporting Ian here on patreon is proving to be the best investment

Nate

You guys are not only incredible artists but amazing educators too! Thank you!

Nathan Vegdahl

I watched through the first part of Steve Yedlin's video that you linked, and he's actually in agreement with me. He mentions something called "metameric failure" around the 17 minute mark, which is the critical thing that makes his process not fully color accurate, which he acknowledges. At this point tetrahedral interpolation is fairly standard for 3D LUTs (and is supported in OCIO, for example). But I don't know when that video is from, so it might have been newer at that point? Not sure. The main benefit is just that it ensures that your neutral colors (whites and greys) stay neutral, as long as the LUT itself also leaves them neutral. It's not especially fancy, but was certainly a cool insight from whoever came up with it!

Zeke Faust

What Yedlin has done to bring awareness to image science is really wonderful. He's demonstrated that a "look" is not something we are forced to choose, but something we create for ourselves, provided we have the knowledge. I actually made a port of the tetra tool for blender. It's a pretty versatile and powerful tool which allows you to remap colors in a much smoother way. I made a version for the compositor as well as the shader editor More info and download link here: https://www.youtube.com/watch?v=S4irqcya2iA

Nathan Vegdahl

I finished watching the rest of Yedlin's talk, and it's really exceptional, and he obviously really knows his stuff (more so than me, honestly). Thanks for the link Sam!

NickTricc

Hey Nathan! About the iPhone app Filmic Pro and color: There’s an option called “Linear” in the color management! Should I use that instead of “filmic/filmic log” when doing VFX? (Would that make the process simpler?) Ps. Good stuff! Your tone, clearance in speech, the information.. You nailed that video! Good stuff!

Nathan Vegdahl

Hey Zeke! Ah, I may have misunderstood Sam's question, then. I thought he was asking about LUT interpolation (e.g. linear vs cubic vs--for 3d LUTs--tetrahedral). But if he was asking about a tool like what you've made here, then I have no idea. I don't actually do any grading work myself. When it comes to color, most of my knowledge is more on the theory/science side of things, as opposed to the practice side of things where I still have some pretty large gaps of knowledge (which will become more obvious as the series gets into more complex topics). I'm still hoping my series will be useful to people, though (finger's crossed). Really looking forward to more of this discussion!

Samuel Jerome Mason

Glad the talk was helpful!! And amazing to see you've already got this in blender Zeke!

john voss

This was amazing! I know you're just getting started, but I need to know this stuff from the ground up so this series will be perfect for me. Thank you Nathan!

Richard Blow

I'd also like to know this, though it sounds like phones could be performing other changes to the images. Thanks Nickolai for digging into this subject! I know phones are inferior to mid-grade DSLR cameras, but I like their convenience. Also, because so many people use phones, I think their video gives the feeling of reality, which is a great place to start when doing VFX.

NickTricc

Okay, im starting to get really good results very easy with the filmic app!! - Filmic Pro Settings: 10Bit Color and whatever framerate/resolution you want. (dont use stabilization if you want to motion track it) In the color settings, set it to linear (between natural and HLG) - Blender setting: Match resolution and framerate. In the color management settings, under "sequencer" chance it to linear. View transform i have set to standard aswell. Now just match the lighting as you please and it renders very good very easely! Cant believe how much easier it is to match to be honest! Try it out if you like! let me know if i should do a quick video or something to clear things up!

Richard Blow

I think you're onto something. One thing I notice is that the file sizes for the 10-bit footage are very low compared to the PRORES footage so I imagine there is a lot of data loss when using 10 bit.

Richard Blow

Oh, one other thing. I notice my linear footage is really dark. I think Nathan explains why the linear curve looks darker, so I added Gamma to the footage (I set it to 2.2 as a guess) and it set the brightness to something that looked natural, but then I noticed a ton of artifats in my video. It was shot in relatively low lighting so maybe it would've been fine with more lighting, but the PRORES footage has no artificats when imported into blender.

Nathan Vegdahl

> set it to linear (between natural and HLG) LUT Maker supports HLG (Hybrid Log-Gamma), so you can use that too. > Just scanning this document seems to give a few insights of what the transfer function curves look like in Filmic Pro Not only that, they actually give the formula for it, which is what I need for implementing it. They claim it's patent pending, but I have a really hard time imagining that would be a valid patent. They try to make it sound all innovative and whatnot, but everything they discuss in the paper is widely known to anyone who works on this stuff. All they've actually done is created another log-based transfer function. Nevertheless, the fact that they put that patent notice prominently at the top of their whitepaper makes me think they may be a litigious company. And given that the app already supports both HLG and linear anyway, it's probably not worth implementing their custom curve.

Carter Burr-Kirven

Recording directly to linear in 10-bit ProRes strikes me as risky (especially on a phone!), there's a reason we use gamma'd-up or logarithmic encodings in 8- and 10-bit formats! There simply aren't all that many bits to go around, and saving in linear wastes a huge portion of those bits on the brightest couple of stops, leaving only a couple for the midtones of your image where the human eye will actually perceive detail. A float format like EXR, built for linear data, uses an exponential encoding, sort of like scientific notation (remember high school?), so the precision is most accurate close to the darks and midtones, where the detail matters, and falls off the further away you get, where it doesn't matter if your specular highlight is 165.3 or 165.4. All that is to say, correct me if I'm wrong here? but I'd be very cautious of using that Linear gamma setting when you're only recording 10-bit (sounds like a lot, certainly better than 8-bit, but even in 10-bit you'll use 512 bits for the brightest stop of the image, 256 for the next., 128 for the next, and here we are, only three stops in, hardly even to the midtones yet, and you've got 64 brightness values available for your next stop! By the time you're in shadows, you might have like 8)

Ignacio Matey Higueras

I don't understand why the data after the transfer function is more efficient than when is linear. It shouldn't be the same information (same quantity) but transferred in a different (transformed) way?

Matthias Wenigwieser

Colors in the real world have many millions of possible brightness levels. Our image file formats store brightness (lumincance) in 8 (or sometimes 10 or 12-bit), which gives you only 256 possible values with 8-bit color. Let's say your camera sensor can distinguish 10,000 levels of brightness, but your image data format has only room for 256 levels of brightness (like any image format with 8-bit color, 8 bits giving you 256 possibilities). If you simply compress 40 brightness levels from the sensor into every brightness level of the image (linear color space, 40 * 256 = 10,000), the problem is that you use a lot of your 256 brightness levels on very high brightness values that look very similar to the human eye. The very darkest regions of your image where the human eye can notice the smallest differences are compressed in the same way. So, by using a transfer function, you split up your 256 possible brightness levels by giving over the first 90 or so to the darkest 10% of the image (where the human eye needs that kind of detail) and sacrifice the detail in higher brigtness levels (where the human eye doesn't care). Thus, you have made better use of the available 256 levels of brightness by using more of them where the will make a visible difference. The result is that after applying the transfer function, you have lost 97.44% of your brightness information (256 is 2.56% of 10,000 after all), but you have lost a lot less in the darker areas where detail is more important. By doing that, you have sacrificed detail in the brighter areas, so there your actual loss will be even bigger than 97.44%, but that hardly matters to the human eye.

Diego Nossa

Great video thanks a lot Ian and Nathan! Very well explained! I've been struggling lately matching photography and CG for more accurate compositings in Blender and although I tried different color profiles, googled everything I could on how to do it properly. I was never able to figure out the right way to go through this workflow. I read many times "...work on linear" but that really never meant anything to me until now with your clear explanation. This video explains a lot of the issues when dealing with images from the camera and color space in Blender.

Nathan Vegdahl

Yeah, as far as my own understanding goes, you're absolutely right, Carter. Honestly, I'd be slightly wary of linear with anything less than 14 bits (depending on dynamic range), and *definitely* wary for anything under 12 bits. Although that's just a gut feeling--I haven't worked out the math for that. In any case, doing *some* kind of non-linear encoding (at any bit depth) is generally going to be a win. And going with HLG is probably the best bet here: it's a defined standard and supports high dynamic range. (Also, I'm glad you mentioned floating point! I was considering mentioning that in the video, but I didn't want to overload people with an onslaught of topics. Figuring out what to include and what to leave out of these videos is honestly really hard...)

Ian Letarte

Brilliant! Nathan is such a good teacher

Dave Wrath

Excellent video. I work in colour at a printing company so I've only ever looked at it in depth RGB to CMYK, this felt like the half of my brain that was missing. Looking forward to the subsequent parts. Do you think the bias to shadows (helpful to see prey or predators) in the human eye is an evolutionary created mechanism, like how we see more shades of green than other colours?

Zeke Faust

almost all human senses have some sort of logarithmic curve, likely for evolutionary reasons as you suggested. A lion is scary. But 256 lions are not 2^8 times more scary than 1. Sound, vision, pressure etc. it's called weber's law

Nathan Vegdahl

It's not my area of expertise, so I can only make a guess. As Zeke mentioned, our vision is approximately logarithmic. My suspicion as to why that's the case is that perhaps the ratios between values are more useful than absolute differences. If your eyes work in terms of brightness *ratios*, then (for example) turning up the brightness of a light still leaves things looking basically the same: the ratios between illuminated objects haven't changed, only their absolute differences. And when you develop a number system where equal increases in your numbers actually represent an equal increase in ratio, you've just created logarithms.

Dave Wrath

I'm in Australia, so I'm far more concerned with small venomous things in the shadows than I am with lions, but I get your point. Great responses, and some good reading on Weber's Law. Cheers!

IanHubert

I think my fear IS linearly proportional to number of spiders.

chriskon

interesting topic and well explained, learned a lot from this!

David McSween

Really nice explainer Nathan, I'm certainly looking forward to subsequent installments. I was just wondering if any of your color stuff had been run through the fiery forge of Troy?

Agustin Eguia

Always nice to have things demistifyed like this... takes all the buzzwords out from it so it's clear and simple.

Alex Schenke

I'VE BEEN SEARCHING EVERYWHERE FOR SOMEONE TO EXPLAIN COLOUR MORE. THANK YOU!!!!!

Eric Elliott

Incredibly helpful! Thanks so much, you guys!

Miklas Hoffmann

Nathan! Thank you for the Shakify PlugIn.. Do u think it is possible to have a funktion that converts everythink into keyframes? (Good for Renderfarms which will disable Drivers like Sheepit)