WHITE BALANCE, RGB SLIDERS & SATURATION

These affect the balance, purity and intensity of colors, and are useful for controlling color casts.

White balance helps ensure that neutrally shaded objects within the original scene appear neutral in the image. This often improves colors dramatically, and is required with virtually every shoot. The "Kelvin" slider adjusts the relative warmth or coolness, whereas the "tint" slider adjusts the magenta-green balance.

Most prefer to first change the Kelvin slider since this often needs more adjustment, then to fine-tune using the Tint slider. The "Pick WB" dropper tool can automatically estimate Kelvin and tint if clicked on a known light-shaded, neutral object. Alternatively, sometimes having technically accurate color isn't the goal. In these situations, white balance can also be used creatively to simulate late evening light (with a higher Kelvin value), or an overcast day (with a lower Kelvin value).

The RGB sliders affect color balance similar to the white balance controls, except the former uses three sliders whereas the latter is simplified to two. Having three sliders permits brightness adjustments if all are changed in unison, but this can also make it more difficult to adjust the color balance in isolation. The RGB tool is primarily for those that find it easier to think in terms of red, green and blue instead of warmth/coolness and magenta/green tint. Regardless, white balance should always be specified as intended first, since this ensures the most accurate colors; afterwards the color balance can be fine-tuned using the RGB sliders.

The saturation slider affects color intensity. This can make images more vivid and appealing, but can also exaggerate a color cast if the white balance isn't precisely neutral. Saturation can also be influenced by other settings, such as contrast and curves, so finalizing this slider is often saved for the last stages of grading. Some prefer to start with a small saturation increase of 1.1 or 1.2 when they start grading though, then to adjust this again later.

ISO, FLUT, BRIGHTNESS & EXPOSURE

These shift all tones brighter or darker, and are useful for fine-tuning exposure.

The ISO, FLUT and brightness settings all work much like ISO with traditional film and stills cameras, with one difference: they are designed to avoid highlight clipping and crushed shadows when increased or decreased as long as these were not present in the original capture. Each has an identical effect on the image; they're just expressed using different units, and ISO only permits discrete values. Each unit change in FLUT is equivalent to a 1-stop change in ISO. The brightness slider is better for fine adjustments since it has the least influence of all three.

The one outlier is the exposure slider, which can cause highlight clipping if pushed too far much like traditional exposure with film and stills cameras. Each unit change in exposure is otherwise equivalent to changing FLUT.

SHADOW, DRX, CONTRAST & CURVES

These affect the relative distribution of tones within an image and strongly influence the overall look of grading.

The shadow slider sets the black point, which determines the left-most extreme of the image histogram. If changed, this is almost always adjusted to the left, which can improve image contrast dramatically if no portions of the image were fully black to begin with. When adjusting, pay close attention to the shadow clipping indicator on the very left side of the histogram; images typically benefit most from a shadow slider that is moved as far left as possible without inducing shadow clipping.

The DRX slider stands for "Dynamic Range Extension," and attempts to recover clipped highlights wherever only some of the color channels are blown. The effect is subtle though, and doesn't restore full color information, but can be helpful with slight overexposure by fixing color shifts in the extreme highlights.

The contrast slider stretches or contracts the midtones relative to the highlights and shadows. This can be helpful when trying to compensate for lighting which is too hard or soft. An often pleasing side effect is that higher contrast also tends to increase midtone color saturation.

The curves tool is perhaps the most powerful tool within the looks panel, and is capable of controlling the black/white points, color balance and tone-specific contrast all in a single tool. In theory one could even replicate the results of all the previously mentioned tools combined. Such flexibility comes at the expense of simplicity though, so this tool really deserves an article of its own.

In short, it works by using a curved line to map input tones (on the horizontal axis) into output tones (on the vertical axis). Similar to the histogram, the far left and right correspond to black and white, with a continuum in between. A higher slope increases image contrast in corresponding tones, but also requires a lower slope and therefore lower contrast in the other tones.

The key is to start with subtle and gradual curves adjustments, since even small changes can have a big impact. The most common curve is the "S-curve," which enhances midtone contrast similar to increasing the contrast slider. This is created by moving the center-left slider down and the center-right slider up:

A curve can also be applied separately to each of the red, green and blue color channels, in which case things get more complicated. This is most commonly used to adjust the color balance only for specific tones. For example, one could increase the height of the red curve only for the highlights, which would warm the highlights while preserving the previous color balance for the midtones and shadows:

Note how the red color curve warms highlights in the sky, water and snow without affecting the shadows.

IN PRACTICE

The order in which each setting is applied varies, but it's usually good practice to start with the steps that have the potential to impact the most subsequent steps, or which make those steps easier to visualize. As a general guideline, first specify white balance and check to make sure that the color space and gamma are at their commonly used settings. Then adjust the exposure, shadows, highlights, tones and contrast. Then finally, adjust color saturation and potentially sharpness.