When Should You Color Grade in Log vs. Linear?

Most of my articles are about doing a little issues in a log house and different issues in a linear house. But one factor that I’ve by no means coated is the distinction between log and linear colour areas. When ought to we use log versus linear house? What is the distinction? And what instruments ought to we be utilizing in each areas?

I’m going to reply these questions immediately. My objective is to offer you a hands-on, utilized, and sensible information to log vs. linear with out a bunch of sophisticated colour science or math. I simply need to have a look at how these two areas work, how they behave, and the way we will get probably the most out of every utilizing DaVinci Resolve.

How I modify distinction in log

Let’s begin by taking a look at log house. For anybody who’s unfamiliar, log is the default grading house utilized in scene-referred, colour managed workflows, which is how I all the time work. For this text, I’ll be working within the DaVinci Wide Gamut Intermediate working colour house, which is certainly a log house. 

When I take into consideration what I love to do in a log house that I wouldn’t need to do in a linear house, the very first thing that involves thoughts is distinction changes. Let’s check out an instance so you’ll be able to see what I imply.

Take a have a look at the shot above. The publicity feels tremendous, however I need to form the low finish of the picture a little bit bit. To do that, we’ll first add a serial node. 

Next, I’m going to restrict issues to the world under center grey. To do this, I’ll go to the Gallery, go to my utilities, and add my useful DaVinci Wide Gamut grey patch to the brand new serial node.

This is just my publicity chart DCTL (DaVinici Color Transform Language) and you will get a free obtain of it here. I’ve set its Total Steps worth to 1 and I’ve turned off Show Ramp. Dragging this DCTL onto my new node offers me a pure patch of DaVinci Wide Gamut grey. 

The subsequent step is so as to add one other serial node. Then, go to Custom Curves and gang the channels collectively by clicking the chain icon. 

After that, use the eyedropper device and click on on the DWG grey patch within the timeline. This ought to provide you with an anchor level proper on that tooth on the decrease finish of the Custom Curves. 

Now that we’ve achieved that, we will delete the node holding the DWG Gray. Then, go to the Custom Curves and begin drawing distinction down on the low finish of the picture. I typically open issues up a contact on the very backside.

This is simply my aesthetic choice. My manner of doing issues is just not roughly right than every other manner. This methodology is simply one thing I love to do by really feel and by eye to offer me a picture that I like taking a look at.

Log and the human eye

Adjusting distinction is one thing I solely ever need to do in log. If I attempted to do the earlier instance in a linear house, my working vary could be a lot smaller. The response of my curve device would additionally really feel bizarre, sensitive, and tough to work with. In common, I’d have a tricky time adjusting distinction in linear as a result of issues wouldn’t really feel as perceptually aligned and intuitive as they do in a log house. 

Log house is rather more aligned with the human eye than linear house. That’s as a result of human eyes work on a log curve slightly than a linear one. You can consider linear house as a modeling of bodily gentle. It’s what occurs out in the true world when issues get brighter or darker. Log areas, then again, work extra like our eyes do. For instance, if I have been to double the quantity of sunshine within the room I’m sitting in, I’d probably not understand it as a doubling. I’d understand one thing much less.

A great way to consider it’s that log areas are good at modeling issues which can be perceptual and intuitive, equivalent to preferential distinction changes. Linear responds in a extra general manner, which we’ll have a look at later.

Look growth in log

Look growth is all concerning the preferential aesthetic manipulations we mentioned in our earlier instance. None of those aesthetic decisions are proper or flawed, they’re simply primarily based on what we need to see, and they’re going to really feel extra intuitive and simpler to perform in log as a result of log house is extra aligned with how our eyes work.

Let’s transfer on to shot quantity two, which is one other nice instance of how nicely look growth works in log. 

I already take a look in place on this timeline, however I need to cool off the shadows. To do this, prepend a serial node on the timeline stage and comply with the steps we used within the earlier instance to get a DWG anchor level: Go to the Custom Curves, seize the DWG Gray patch, create a brand new serial node, and use the eyedropper to set an anchor level.

Next, go to the upstream node, un-gang the colour channels, and choose solely the purple channel. Grab the purple curve and drop it down on the decrease finish of the Custom Curve. 

Doing this causes the picture to lose some purple. This cools off the shadows, successfully making them a little bit extra cyan.

This is a preferential perceptual adjustment that is smart and feels intuitive and simple in log. It wouldn’t really feel almost pretty much as good if we had achieved it in a linear house. Look growth is all about aesthetics and preferential changes, so it really works higher in log. An adjustment like this instance could be very tough to realize in a linear house.

Playing elevate and achieve in opposition to one another

Let’s transfer on to instance quantity three. The methodology I’m about to point out you is likely one of the first strategies that I discovered after I started colour grading. It’s all about enjoying elevate and achieve in opposition to one another.

Let’s begin in our Primaries. First, transfer the achieve northwest to heat up the picture. Next, transfer the elevate southeast  to get hotter shadows and cooler highlights. This is one thing I do primarily based on what I like. I’m simply feeling my strategy to a outcome that appears good to me on display screen.

I wouldn’t be capable to work this fashion in linear house due to the way in which the maths works. That makes elevate and achieve one other nice instance of one thing we might actually solely do in a log house. This methodology, together with look growth and manipulating distinction, are all perceptual, intuitive, feel-based issues that simply work higher in a log house.

When log doesn’t work

I like working in log areas. There’s a motive that it’s the default area for colour grading. But there are some issues that log isn’t good for. Let’s transfer on to the following shot and speak about linear house.

Here’s a shot that must be opened up. The publicity is type of low, proper? 

If we work in log, what are we going to make use of to open up this picture? What is the closest analog to publicity out there to us if we’re working in a log house? That’s proper, it’s the offset. 

So let’s go in and open up the offset utilizing the topic’s pores and skin to discover a stage we’re proud of. Skin is usually what I have a look at after I’m making nearly any type of adjustment. First and foremost, I all the time need to guarantee that I’m making my topic look nice. But have a look at what occurs after we’re grading in log. 

There’s some extent the place our shadows begin to milk out, proper? You can see it clearly within the histogram under. After the offset adjustment, there’s an enormous hole between zero and the underside of the picture. This is occurring as a result of the response of the Offset management in log house is just not linear. It is just not uniform up and down the tone scale.

The downside is that we’re getting a sooner response within the shadows than within the midtones or highlights. As a outcome, we would wish to repair the picture by going again in and dragging the elevate again down, which could trigger me to want to carry my offset again up even additional.

Now we’re in a dynamic that I attempt exhausting to keep away from in colour grading, which is making changes that demand compensations. Sometimes that scenario is inevitable. But you’ll be lots nearer to the end line if you may make an adjustment that creates no want for additional compensation. 

Using the HDR Palette

Let’s use one other methodology to check the variations between log and linear. We’ll do that through the use of the Global colour wheel within the HDR palette as a result of that device applies linear achieve to the picture. It’s truly doing the identical factor as setting the Gamma on a serial node to Linear and utilizing the Primaries to use achieve.

The solely distinction is within the models of measurement the Global wheel makes use of. The Global wheel makes use of photometric stops, which is a pleasant good thing about working in HDR zones. You can use both methodology, however for this text, I’m going to make use of the Global wheel.

Working with publicity in linear house

Look how a lot much less fogging there may be within the linear house model of this picture versus the log model. That occurs as a result of the response in linear house is extra photometric. It offers a uniform response throughout shadows, midtones, and highlights. Exposure changes are an important hands-on instance of the place linear house shines as a result of we get a cleaner, extra uniform response proper out of the field. And there’s going to be lots much less compensation after we use the linear Global wheel adjustment. 

Now, we should still need to make distinction changes, however they aren’t going to be made as a result of one thing went flawed. They will simply be the extra changes that we need to make as a result of we’ve optimized our publicity. I’m not saying that you’ll by no means have to do the rest to your picture simply since you are working in linear house. But you don’t need to work in an area that’s going to create extra issues so that you can resolve. 

Color steadiness in linear house

So we’ve coated why publicity works properly in linear. It’s extra photometric, and it eliminates these compensation counter-moves that we must do proper after making the preliminary transfer. That identical thought goes to use to paint steadiness. Let’s check out one other picture.

This picture wants to chill off. It’s coming in a little bit bit heat. Let’s begin through the use of our Offset wheel in our Primaries Color Wheels to see a log adjustment. We need to discover a a lot cooler rendering of this picture. Again, I’m primarily utilizing pores and skin tone as a supply of fact for the way nicely I’m doing the job.

The pores and skin tone is feeling good proper there. Now, let’s examine our log colour steadiness adjustment to 1 achieved in linear utilizing the Global wheel within the HDR palette. 

This is a refined instance, however in log, the shadows are cooling sooner than the midtones and highlights. It’s the identical precept that made the shadows milky in our publicity adjustment instance. When we make a balancing adjustment in log to chill the picture off, the cooling occurs faster within the shadows.

Use the slider to see the distinction of log (left) vs. linear (proper) within the histograms.

The non-uniformity and non-linearity of the log adjustment create a necessity for counter changes. But that doesn’t occur in linear, the place there’s a uniform response throughout shadows, midtones, and highlights. 

Wrapping up

This article simply scratches the floor, however it covers the fundamentals of log versus linear that I need each colorist to know once they’re going right into a colour grade. Log works nicely for perceptual field-based aesthetic changes, and linear works for corrective, absolute, bodily issues. In explicit, I need you to be careful for log changes which can be higher achieved in linear as a result of, in linear, there may be much less have to make compensating counter strikes after the very fact.

That’s actually the place linear shines. Linear offers us the precise device to make the precise adjustment with no undesirable uncomfortable side effects. Then we will transfer on and have a look at different facets of our grade as soon as we’ve obtained the fundamentals dialed in. Log helps us make aesthetic, feel-based look selections as a result of it really works in the identical logarithmic style as our eyes do.