PSadv – 01

The first Class is all about identifying, correcting and manipulating colors and luminance in Images with the tools available in Photoshop.

Info: We’ll use masks and selections in this class. Have a look at the Know How Section at the end of this page to freshen up your basic PS knowledge.

Home Assignment

Work along all of the examples below. You’ll find the starting files in the Class Material Folder “for practicing” Save each as a small jpg go to File→ Export→ Export as… (cmd + opt + shift + W) and save your file 1000px wide with quality 70% (see screenshot) and upload it to your folder.

Also try at least five of the other images in the “for practicing”. Upload those as well.

Also try out the technique on your own files for practicing purpose. If you struggle, come along to my office hours.


RGB

We’re going to use the RGB color model for all our color correcting and other work in Photoshop.

RGB images are made up of 3 channels, Red, Green, Blue, that together form the color-image. 

The RGB color model is an additive model wich means that the higher the Value in each channel the lighter the overall color will be. 

The most important info for color correcting is that if the values for R,G and B are the same the result is a neutral tone like white, grey or black.

Info on Color Profiles: I recommend using either Adobe RGB or ECI RGB as a working color profile in Photoshop. We’ll get to more info on profiles and color work flow in a later class. Some of the practice files are in sRGB and Photoshop will ask you when you open them what it should do. In our case just click on Keep Color Profile and your good to go.


Identifying Colors etc.

We’ll start with the tools we need to identify color values and luminosity in digital images.

The Histogram

One of the most common used ways of displaying color/luminosity data in an image is the histogram. You will find it not only in Photoshop but also in any other image software as well as on your digital camera.

The RGB-histogram in Photoshop shows you a composite of the color range of an image by counting all pixels for each of the 256 color intensity levels (in 8-bit). Starting from the darkest parts on the left (0 complete black) to the lightest ones on the right (255 complete white).

This means Photoshop asks each pixel about its R,G and B value and counts the pixels that have the same value. Resulting in the heaps and spikes of the histogram.

Examples

Here are a few example images with their histograms and some explanations that show that it always depends a lot on the content of the image as well as on the information of the histogram, if you want to correct something or not.

Correct exposure. Image shot at daylight with well distributed Luminance. Most detail is in the mid tones. No cut off blacks or whites, no lost details.

Needs fixing!
Underexposed image shot during the day with lots of dark pixels that you see on the left of the histogram. The blacks are not cut off though which means there is some information in the dark tones still and the image can be corrected. (Underexposure in digital photography is more easily fixed as Overexposure – its the opposite as in analogue Photography). Also note the spike on the right of the histogram – thats the glaring white sun that hits 255.

Can this be fixed? Overexposed image with white clipping on the right. The details in the sky are lost (or have never been there). Very hard to fix with correction, if not at all fixable.

Image with a lot of white content but not overexposed. The lightest values (around 244) are not completely white so the sky etc. will still print nicely. Also note how the image still is visible on a white background because of this.

Image with a lot of dark content but still correctly exposed for the sky as the main point of interest. Blacks again are not clipped so there is detail in the shadow still. The thin white line on the bottom right – thats all the stars.

Info panel

In the info panel you can see the values of the pixel you are currently hovering over. Also measurements of your mouses xy-position and selection sizes. In combination with the eyedropper tool the info window becomes very useful.

Eyedropper Tool

The Eyedropper Tool lets you sample colors in the image by clicking. They then become your new foreground color*. But this is not all there is to this tool. You can also add color sampler points. These we’ll use for our correction process.

*In older PS versions the sampling would also work for the background color, if that one was activated in the color window. If you have that problem look at this tutorial from minute 1:00.

Your eyes

Last but not least an important part of identifying color and luminosity issues in an image is your eye and the brain that’s connected to it. You can identify the contents of an image and then decide if what you see needs correcting or not. Sometimes an overly dark image looks great because it was shot in the shadow or at dusk. Other images are very bright and making them darker would counteract their story. Or maybe there is a color cast that represents a certain mood that you deliberately want to keep in your image.


Color Correcting

Now that we know the tools for identifying colors and luminosity, let’s see what we can do, if we decide we want to correct some color/brightness issues in an image.

Color correction vs. grading

Color correction is aimed to fixe color issues like faulty white balance, under- or overexposure and make images appear as naturalistic as possible. The outcome should be an image that looks clean and real, as human eyes would see it in the real world.

You color correct images to have a good starting point for every retouch, montage or creative color grading you want to do later on. Also especially if you want to combine two or more images it’s great if they all have correct starting colors.

Color grading on the other hand is also technical, but more of a creative concern. The color grading process adds atmosphere and emotion to images by coloring in new, often even unnatural ways. Used in Photography but even more in Film, as color palettes are part of the how a story is told. We’ll get to that later on in this course.

Working in photoshop those two areas of color manipulation often fade into each other. So while you might do some correction you maybe also find yourself adding some creative choices in this process as well.

What and when to correct

Here are a few common image problems that you might want wo correct:

  • Not enough light in the image although it was shot at bright daytime
  • To get rid of a color cast that does not add to the overall story of the image or that is only in parts of the images
  • Darker areas are too dark while light areas are looking ok
  • Parts of an image that have a different light temperature than others. (Often happens with different light sources – daylight and artificial light in one shot)
  • White balancing images before combining them into a montage to have a similar color and brightness starting point
  • Giving more contrast to certain areas of an image
  • All combinations of the above and many more

Examples and Tools

In this section we’ll have a look at example images and learn the techniques needed on the way. Have a look at each video. Grab the “Example-…” files I work on in the videos from the “for practice” folder and work along.

Curves Adjustments

Basic Brightness – Levels, Curves explained

White Balance with Curves – Highlights

Color Shift in the Mid Tones

Fixing Highlights and Mid Tones plus Perspective

Color Cast in Highlights and Shadows – new

Working with a color target or grey card – new

Hue/Saturation and Selective Color

Hue/Saturation explained

Selective Color explained

Example

Combining Techniques

Sometimes you only need one of the above to get great results, sometimes you’ll need to use them in combination.

Color cast in part of the image – new

Underwater

The inverted color method for the lost cause

If you have to work with an image that has a really heavy color cast and you can not re-shoot you might want to try this nifty trick.

inverted color


Know How

Curve Adjustments

This video with has no audio – see and try to understand whats happening

Freshen Up

Masks

Clipping Masks

Image Size vs. Canvas Size

Selection Tools – Essentials you should know

Detailed Knowledge:

Selections in Detail

Fill vs. Opacity

New in Photoshop 2021

A few Shortcuts

Choosing the Brush Tool:

Press B on your keyboard to choose the current Brush Tool
Press shift + B to shuffle through the different Brush Tools

Size control:

Windows → Alt + right-click in the document
Mac → Control + Option + click in the document
Drag left and right for Brush Size and up or down for Hardness

Foreground and Background Color

Press X to switch between them
Press D to set them to 100% Black and White

Fill with Foreground or Background Color

To quickly fill an entire layer or an existing selection with a color:
Option + ⌫ (Backspace) → fill with foreground colour
Cmd + ⌫ (Backspace) → fill with background colour
Add Shift to these combinations to save transparency and only fill existing pixels.
You now never ever need to use the Paint Bucket Tool again. Yay!

Sample Color

While using the brush tool you can sample any color on your canvas by pressing Option (Alt) an clicking on a pixel in the image.

TIP: In CC2019 and lower take care your Foreground Color is activated (click on it, it has a frame around it), otherwise PS will sample into the Background Color.