It’s time to dive into some of the terms and concept that brought you modern color correction software. First of all – color grading versus color correction. Many use these terms to identify different processes, such as technical shot matching versus giving a shot a subjective “look”. I do this too, but the truth of the matter is that they are the same and are interchangeable. Grading tends to be a more European way of naming the process, but it is the same as color correction. (Click on any of the images in this article for an expanded and more descriptive view.)
All of our concepts stem from the film lab process known as color timing. Originally this described the person who knew how long to leave the negative in the chemical bath to achieve the desired result (the “timer”). Once the industry figured out to manipulate color in the negative-to-positive printing process, the “color timer” was the person who controlled the color analyzer and who dialed in degrees of density and red/blue/green coloration. The Dale Grahn Color iPad application will give you a good understanding of this process. Alexis Van Hurkman also covers it in his “Color Correction Handbook”.
Electronic video color correction started with early color cameras and telecine (film-to-tape transfer or “film chain”) devices. These were based on red/blue/green color systems, where the video engineer (or “video shader”) would balance out the three components, along with exposure and black level (shadows). He or she would adjust the signal of the pick-up systems, including tubes, CCDs and photoelectric cells.
RCA added circuitry onto their cameras called a chroma proc, which divided the color spectrum according to the six divisions of the vectorscope – red, blue, green, cyan, magenta and yellow. The chroma proc let the operator shift the saturation and/or hue of each one of these six slices. For instance, you could desaturate the reds within the image. Early color correction modules for film-to-tape transfer systems adopted this same circuity. The “primary” controls manipulated the actual pick-up devices, while the “secondary” controls were downstream in the signal chain and let you further fine tune the color according to this simple, six-vector division.
Early color correction system were built to transfer color film to air or to videotape. They were part machine control and part color corrector. Modern color correction for post production came to be, because of these three key advances: memory storage, scene detection and signal decoding.
Memory storage. Once you could store and recall color correction settings, then it was easy to go back and forth between camera angles or shots and apply a different setting to each. Or you could create several looks and preview those for the client. The addition of this technology was the basis for a seminal patent lawsuit, known as the Rainbow patent suit, as the battle ranged over who first developed this technology.
Scene detection. Film transfer systems had to play in real-time to be recorded to videotape, which meant that shot changes had to trigger the change from one color correction setting to the next. Early systems did this via the operator manually marking an edit point (called “notching”), via an EDL (edit decision list) or through automatic scene detection circuitry. This was important for the real-time transfer of edited content, including film prints, cut negative and eventually videotape programs.
Signal decoding. The ability of color correction systems to decode a composite or component analog (and later digital) signal through added hardware, shifted color correction from camera shading and film transfer to being another general post production tool at a post facility. The addition of a signal decoder board in a DaVinci unit split the input signal into RGB parts and enabled the colorist to enhance the correction of an already-edited master using the “secondary” signal electronics of the system. This enabled “tape-to-tape” color correction of edited masters. Thanks to scene detection or an EDL, color correction could be shot-to-shot and frame-accurate, when played back in real-time for its re-encoded, corrected output back to a second videotape master.
Eventually the tools used in hardware-based, tape-to-tape color correction systems became standard. Quantel and Avid led the way by being first to incorporate these features into their nonlinear editing software.
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Color correction software tends to break up its control into primary and secondary functions. As you can see from the earlier explanations, there’s really no reason to do that, since we are no longer controlling the pick-up devices within a camera or telecine. Nevertheless, it’s terminology we seem to be comfortable with. Often secondary controls enable masking and keys to isolate color – not because it has to be that way – but, because DaVinci added these features into their secondary control set. In modern correction tools, any function could happen on any layer, node, room, etc.
The core language for color manipulation still boils down to the simple controls exemplified by the Dale Grahn app. A signal can be brighter, darker, more or less “dense” (contrast) and have its colorimetry shifted by added or subtracting red, blue or green for the overall image or in the highlight, midrange or shadow portions of the image. This basic approach can be controlled through sliders, knobs, color wheels and other user interfaces. Different software applications and plug-ins get to the same point through different means, so I’ll cover a few approaches here. Bear in mind, that since some of these actually represent somewhat different color science and math, examples that I present might not yield exactly the same results. Many controls are equivalent in their effect, though not necessarily identical in how they affect the image.
A common misconception is that shadow/mid/highlight controls on a 3-way color corrector will evenly divide the waveform into three discrete ranges. In fact, these are very large, overlapping ranges that interact with each other. If you shift a shadow luminance control up, it doesn’t typically just expand or compress the lower third of the waveform. Although some correctors act this way, most tend to shift the whole waveform up or down. If you change the color balance of the midrange, this color change will also affect shadows and highlights. The following is a quick explanation of some of the popular color control models.
Contrast/pivot/temperature/tint
Contrast and temperature controls have recently become more popular and are considered a more photographic approach to correction. When you adjust contrast, the image levels expand or stretch as viewed on a waveform. Highlights get brighter and shadows deepen. This contrast expansion centers on a pivot point, which by default is at the center of the signal. If you change the pivot slider you are shifting the center point of this contrast expansion. In one direction, this means the contrast control will stretch the range below the pivot point more than above it. Shift the pivot slider in the other direction for the opposite effect.
Color temperature and tint (also called magenta) controls balance the red/blue/green signal channels in relationship to each other. If you slide a color temperature control while watching an RGB parade display on a waveform, you’ll note that adjustments shift the red and blue channels up or down in the opposite direction to each other, while leaving green unaffected. When you adjust the tint (or magenta) slider, you are adjusting the green channel. As you raise or lower the green, both the red and blue channels move together in a compensating direction.
Slope/offset/power
The SOP model is used for CDL (color decision list) values and breaks down the signal according to luma (master), red, green and blue and are expressed in the form of plus or minus values for slope, offset and power. Scratch Play’s color adjustments are a good example of the SOP model in action. Slope is equivalent to gain. Picture the waveform as a diagonal line from dark to light. As you rotate this imaginary line, the higher part becomes taller, which represents brightness values. Think of the slope concept as this rotating line. As such, its results are comparable to a contrast control.
The offset control shifts the entire signal up or down, similar to other shadow or lift controls. The power control alters gamma. As you adjust power, the gamma signal is curved in a positive or negative direction, effectively making the midrange tones lighter or darker.
Lift/gamma/gain
The LGG model is the common method used for most 3-way color wheel-style correctors. It effectively works in a similar manner to contrast and SOP, except that the placement of controls makes more sense to most casual users. Gain, as the name implies, increases the signal, effectively expanding the overall values and making highlights brighter. Lift shifts the entire signal higher or lower. Changing a lift control to darken shadows, will also have some effect on the overall image. Gamma bends the curve and effectively makes the midrange values lighter or darker.
Luma ranges
The portions of the signal altered by highlight/shadow/midrange controls (like SOP, LGG or other) overlap. If you change the color balance for the midrange tones, you will also contaminate shadows and highlights with this color shift. The extent of the portion that is affected is controlled by a luma range control. Many color correction applications do not give you control over shifting the crossover points of these luma ranges. Some that do, include Avid Symphony, Synthetic Aperture Color Finesse and Adobe SpeedGrade. Each offers curves or sliders to reduce or expand the area controlled by each luma range and effectively tightens or widens the overlap or crossover between the ranges.
DaVinci Resolve includes a similar function within its log-style color wheels panel. It uses range adjustments that can limit the area affected by the balance and saturation controls. Similar results may be achieved by using HSL keyers or qualifiers that include softening controls.
Channels or printer lights
Video signals are made up of red, blue and green channel information. It is not uncommon for properly-balanced digital cameras to still maintain a green color cast to the overall image, especially if log-profile recording was used. Here, it’s best to simply balance the overall channels first to neutralize the image, rather than attempt to do this through color wheel adjustments. Some software uses actual channel controls, so it’s easy to make a base-level adjustment to the output or mix of a channel. If your software uses printer lights, you can achieve the same results. Printer lights harken back to lab color timing, using point values that equate to color analysis values. Regardless, dialing in a plus or minus red/blue/green printer light value effectively gives you the same results as altering the output value of a specific color channel.
This is just a short post to go over some of the more confusing terminology found in modern color correction software. Many applications tend to blend the color science models, so as you apply the points mentioned to your favorite tool, you may see somewhat different results. Hopefully I’ve gotten you in the ballpark, in order to understand what happens when you twirl the knob the next time.
©2014 Oliver Peters
Magic Bullet Suite 13 is comprised of seven plug-in products, which include Looks 4.0, Colorista IV, Denoiser III, Cosmo II, Mojo II, Film, and the newly added Renoiser. The tools are cross-platform compatible (macOS or Windows), but depending on the editing or compositing software you use, not all of these plug-ins work in every possible host. All of the tools will work in Adobe Premiere Pro or After Effects, as well as Apple Final Cut Pro X. Magic Bullet Looks 4.0 provides the broadest host support, including some less common choices. Looks supports After Effects, Premiere Pro, Final Cut Pro X, Motion, Magix Vegas Pro, Avid Media Composer, DaVinci Resolve, EDIUS, and HitFilm Pro. Colorista only supports the Adobe and Apple hosts, while the other tools support the bulk of possible choices, with the exception Media Composer. Therefore, what you cut or composite with will determine what your best purchase will be – full suite or individual plug-ins.
The big selling point of this release is GPU acceleration across the board using OpenGL/OpenCL. This provides real-time color correction. There are plenty of refinements throughout, but if you are an Adobe user, you’ll note that Colorista IV has embraced Adobe’s panel technology. If you are comfortable with Premiere Pro’s Lumetri Color panel, you can now instead work with Colorista, in this exact same manner. I’ve dabbled a bit with all of these tools in various Avid, Apple, and Adobe hosts. While performance is good and certainly improved, you’ll have the best experience in Adobe After Effects and Premiere Pro. Another advantage you’ll have is Adobe’s built-in masking and tracking tools. Want to isolate someone’s face and track a Colorista correction to it during a moving shot? No problem, since the Adobe’s features augment any installed plug-in. As an editor, I like to do most of my work within the NLE, but honestly, if you want the best total experience, use these tools in After Effects. That’s where everything shines.
I won’t dive into each specific feature, since you can download a free trail version and see for yourself. Plus, you can reread my Magic Bullet Suite 12 review, as many of the main features are similar. But let me note a few items, starting with Looks. This is the grandaddy plug-in of the group, which actually runs as a mini sidebar application. Apply the plug-in, click the “edit” button, and your reference frame opens in the standalone Looks interface. It includes a wealth of tools that can be applied, reordered, and adjusted in near-infinite variations to get just the specific look you desire. There are three helpful features – grading head starts, the ability to save custom presets, and a looks browser. The browser offers a ton of custom presets with a small thumbnail for each. These are updated with the reference frame and as you hover over each, the main viewer window is updated to display that look, thanks to GPU acceleration. If you want to start from scratch, but not sure what the best tools are to use, that’s where the head starts come in. This section includes six starting points that include a series of correction tools in a preset order, but without any tweaks yet applied.
Colorista IV is another tools that’s received a lot of attention in this build. I’ve already mentioned the panel, but something really unique is the built-in Guided Color Correction routine. This is designed to guide novice and even experienced editors and compositors through series of color correction steps in the right order. Colorista also gained temperature and tint controls, RGB point curves, log support, and LUTs. The addition of integrated LUTs fills a gap, because Red Giant’s separate LUT Buddy tool has been dropped from Suite 13.
The other tools have also gained added features, but let’s not forget the new Magic Bullet Renoiser 1.0. This is designed to give cinematic texture and grain to pristine video and CGI footage. It includes 16 stock presets ranging from 8mm to 35mm. These are labeled based on certain fanciful styles, like “Kung Fu Fighting” or “Classic 35mm”. Renoiser’s settings are completely customizable.
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