After/Before Levels
All images deserves a little closer scrutiny with regards to hue, tone and contrast. Practically with every image I open into Adobe Photoshop, I call up the Levels dialogue box to ensure that the image is at it’s best.
This tutorial will introduce you to a single method for correcting colour and contrast within your image via Levels. Before you start, if you haven’t already done so, I’d recommend you take a look at my ‘Photoshop Levels – Fixing Contrast – Black & White‘ tutorial to establish a good foundation knowledge of Levels.
Levels: Colour Channels
Before we begin, I think it may be worth while taking a quick look a channels. A channel is a ‘plate’ of tonal information that represents the strength of a particular colour, ie ‘Red’ (in ‘R’GB). A channel in itself is little more than a grayscale image (0-255 with 256 individual shades). In colour imaging, multiple channels work together and combine as a ‘composite’ to show millions of visible hues and shades.
RGB: Red, Green, Blue. Used for screen output, i.e. web use, on-screen presentations, video, etc. Up to 16.7 million possible hues and shades (256*256*256=16 ,777 ,216 colours).
CMYK: Cyan, Yellow, Magenta, Black (or Key). Used to print. This time an additional channel (256*256*256*256 = 4, 294 ,967 ,296 colours)
For more information on channels, please read ‘Photoshop: Color Mode | RGB – Grayscale – CMYK‘.
Tweaking Levels
Fig.1 Levels Dialogue Box
Open up a colour image that is a little discoloured, faded or dark. Let’s keep things simple and stick to an RGB image for the time being. The following principle can be applied to a CMYK image in exacting the same way.
We will try and put a little life back into our image using Levels. If you are struggling to find a good example to play around with, then you can use my example photograph (RGB).
As you can see from my image, there is a lot of room for improvement. Your photo might not be as extreme as this, but the following exercise can be applied to the vast majority of colour digital images.
Step 1: Calling up Levels
With your image open, call up the Levels dialogue box: (Menu) Image->Adjustments->Levels or use the quick keys ‘CTRL/APPLE L’ (recommended method). The Levels dialogue box should now appear (fig.1).
Step 2: Selecting a Channel
Fig.2 Red Channel
At the top left of the Levels dialogue window, you should see the ‘Channels’ drop down menu. It will be set to ‘RGB’ (composite mode) by default. By dragging the black, white and gray pointers around, you can only alter the overall contrast and light/dark. So, unless you are confident that the colours within your image are correctly balanced, ignore this channel mode.
From the Channel drop-down, select ‘Red’. Now perform the same adjustment principles as you would with a greyscale image – see ‘Photoshop Levels – Fixing Contrast – Black & White‘. (Fig.2)
Step 3: Repeat process through all other channels
Levels Fixed
After tweaking the first channel – bringing the black and white points into the tonal range (seed Fig.2), select the next channel and repeat this process until all channels have been tweaked.
Your image should now looked great. If the contrast has improved, but the colours are a little out, then try this:
If your image is a little on the blue side, open the Blue channel and drag the gray mid-point (middle) to the right a little.
If your image is too red, open the red channel and drag the graypoint to the right…you get the point.
Step 4: Committing changes
Okay, this isn’t really a points – just click on OK to finalise this process. A stunning result!
