Giorgio Trucco – RGB Editing Workflow

Introduction:
This article is the first installment of a series of articles designed to help you create a print-ready Master File, starting from an original, unedited, image. The method outlined in this article applies to both digital and film-scanned images, and is based on a workflow that I developed over the course of many years, and which has served me well for being extremely reliable and productive. As with everything in Photoshop, this method is not the only way of creating a top-quality Master File, and I share it only as a guideline for those interested in learning how to achieve quality results using a systematic and consistent workflow. I encourage you to use it as a baseline for finding, and refining, your own editing workflow.

Series Outline:
This series is divided in seven parts, following a logical editing sequence:

Part 1: Setting White and Black Points
Part 2: Setting White and Black Points on images that don’t have whites or blacks
Part 3: Global Contrast Adjustment
Part 4: Local Contrast Adjustment
Part 5: Edge Burning, give your image an edge!
Part 6: Organizing your files, saving the Master File
Part 7: Output Specific Resizing and Sharpening

Enough said, let’s digg into it!

PART 1 – White and Black Point Adjustment:
If you are a digital photographer, working in RAW, you are already developing your files using a RAW converter like Adobe Camera RAW for Photoshop, Capture One or Lightroom. If you can achieve all of your desired edits in the the RAW converter, the rest of this article will probably be of little interest to you. In my experience, though, I always end up with a file that is close to what I want but not -exactly- what I want and, as a consequence, I rely on Photoshop for the the final fine-tuning.
Please note that there are advantages in setting the White and Black points in RAW mode, before converting the image. The concepts described in this article still apply, you just need to do the adjustments in the RAW converter.
If you are a film photographer, on the other end, you know very well that no image comes out of the scanner even close to perfect, and substantial editing in Photoshop is always required.

When we have the image open in Photoshop, it’s important to spend some time evaluating the inherent qualities of the image. The first questions I ask myself, while looking at the image, are: “Does the image contain areas that are supposed to be white, and black?”, and “Does the image have any unwanted color cast that I wish to neutralize?”.
In the image below (an image of the world famous Monument Valley that I intentionally shot using a light magenta filter to create a working example of an image that definetely needs correction), we notice a strong magenta cast. We definitely want to remove this color cast. Also, by looking at the image histogram, we notice that the image lacks both true whites and true blacks, and we know that, with very few exceptions, every image should extend across the entire tonal range available, which, for an RGB image, means 0 to 255.
We also notice that the image does have areas that are supposed to be white and black, like the brightest areas in the clouds, and the shadow under the bush, close to left edge. These areas will be be chosen as target areas for adjusting the white and black points.

Before starting any color correction, we should make sure to have all the tools you are going to need available and visible. The basic tools we are going to use are: Info, Histogram and Layers palette.
The first thing we need to do is finding the brightest and darkest areas of the image that need to be remapped to white and black and, to do so, we can use a -temporary- Threshold adjustment layer.
The Threshold command converts images to black and white, depending on the level specified by the user as the threshold. All pixels lighter than the specified threshold are converted to white; all pixels below the threshold are converted to black.
Let’s create a new Threshold adjustment layer and let’s set the threshold level to 255. This turns the entire image to black, since the are no pixels as bright as 255.

Now we start lowering the threshold level, until a few pixels start turning white. The first pixels turning white from black are the brightest pixels in the image.

Make sure that the first visible patch of white pixels coming out of the black correspond to the actual area of the image you want to use as a target for the white point adjustment. Sometimes you’ll need to ignore single spiking pixels scattered here and there in the image.
Once we are happy with the selection, we place a color sampler centered in the target area. I recommend setting the sample size to 5×5 average, as a minimum, to make sure you don’t base your edits on the value of a single pixel.
Now we can set the threshold to 0, which will turn the entire image to white, since there are no pixels as dark as 0. We start increasing the threshold level until a few pixels start turning black. The first pixels turning black from white are the darkest pixels in the image.

Again, we want to be sure that the first patch of black pixels coming out of the white correspond to the actual area of the image we want to use as a target for the black point adjustment. Once we are happy with the selection, we place a color sampler centered in the target area.

At this point we have two color samplers strategically placed in the brightest (#1) and darkest (#2) areas of the image, allowing us to precisely monitor the black and white point adjustment. The readings of the color samplers RGB values, in the info palette, can help us better understand what we see.
The highlight values are RGB=220, 187, 226. As we can see, the green channel is significant lower than both the red and the blue channel, and this explains the strong magenta cast that we see in the image (magenta, as a matter of fact, is the complementary color of green).
The darkest area of the image reads RGB=26, 15, 12. In this case the red channel is stronger, as expected from the diffused red light coming from the sand.

We are now ready to make the adjustments. The goal is to produce neutral highlights and shadows. For the highlights I always aim at RGB=250, 250, 250 to make sure, especially with inkjet printers, that there is some texture left in the brightest areas of the image. Setting the highlights at RGB=255, 255, 255 translates to no ink being deposited on the paper, therefore your whites will become paper white, which can often look dull.
For the shadows I normally aim at RGB=10,10,10 to avoid having blocked shadows as pure black, without any hint of texture.
Let’s open a Curves adjustment layer, and let’s work on the individual RGB channels. I’ll show here the Red channel adjustment in details, as an example. The procedure is then repeated for the Green and Blue channel.
We open the Curves tool and we select the Red channel. Then we select the point in the upper-right corner of the curve window, corresponding to Input and Output Values of 255. We start lowering the Input value until (at Input= 224) the modified Red value (which we can read right of the slash) of the highlight Color Sampler #1 reaches 250.
Now we select the point in the lower-left corner, corresponding to Input and Output Values of 0 and we start increasing the Input value until (at Input=18) the modified Red value of the shadows Color Sampler #2 reaches 10.

We now select the Green channel and repeat the same procedure. Same with the Blue channel. At the end of the process, we get an image with highlights set at RGB=250 and the deepest shadows set at RGB=10. See the image below:

Conclusion:
I regard the white and black point adjustment as the first step in my editing workflow, and one of the most important. It is extremely powerful and allows the user to achieve multiple results in one move.
With it we can:

# extend the tonal range of the image across the entire available range (0-255 in theory, reduced to 10-250 for practical printing purposes)
# neutralize both shadows and highlights
# get rid of major color casts

And, most important, we can achieve all of this with a numerical approach, that is both sound and repeatable.
Below we can see how dramatically we enhanced the initial image, in terms of both dynamic range and color cast removal, using a single adjustment layer.

Feel free to experiment with this workflow, and aim at finding what works best for you!
In the next installment we will discuss how to achieve similar results on images that do not have areas that can be used as targets for black and white, i.e. images that have a natural, desirable color cast.

Giorgio Trucco is a Color Management consultant, a Photoshop trainer and a professional photographer, specializing in wildlife and landscape photography. Giorgio teaches and leads African photo safari workshops through his latest creation, AdventurAfrica, an independent educational guide service that aims at becoming the recognized point of reference for African photo safaris and photography workshops. You can find more information about AdventurAfrica scheduled photo safaris and workshops here.

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