Robert D Feinman

A Better Way to Boost Saturation

One of the issues when printing a photograph is making the colors strong enough to compensate for the flattening effect that occurs on printed papers.

Here is a small part of an image of a tree which is turning color. Taken on color negative film and then scanned in.

This is a screen grab and not the actual file that would be saved, so there may be some slight differences especially in the apparent sharpness. Notice the generally dull colors.

Full range
Original Image

First we apply an overall curves layer to compensate for the low contrast scan. The details of this are not important for this discussion, but the primary objectives is to improve the overall contrast and brightness of the scene.

The next step is to create an adjustment layer using the saturation tool. Here is the dialog box showing the values I selected. Notice that I'm only trying to boost the saturation of the yellow greens that are the dominant colors of the tree.

Saturation Dialog

Here is how my layers stack up at this point.

By using adjustment layers I can go back and adjust the values since the saturation may affect the overall contrast and brightness made with the curves layer.

Saturation Adjustment Layers

Here is the final result of the two adjustment layers. It is clear that the colors in the tree are more vibrant. They actually are closer to what the original scene looked like.

There has been a trend over the past few decades to have photographs appear more vibrant. The film makers still compete on the basis of who can produce the most saturated look. Sometimes this is not what is wanted, especially for things like portraits and weddings. That's why both Kodak and Fuji make more "natural" color negative films as well.

Digital camera makers have entered into the saturation race as well, with many cameras having a special setting to boost saturation. Whether this is desirable I leave to your personal preferences.

Five Percent Histogram
Final Saturation Result
Now I show an alternative method to boost apparent saturation. The first step is to chose the area of interest. I used the magic wand tool, but any tool which gives you the selection area you wish is fine. If there are many areas of similar color that you want to change the Color Range tool might be appropriate.

Notice that the selection doesn't include all of the area. I don't need to select the dark areas, because I want them to remain dark and mostly colorless.

Selected Area
Here is the curves dialog. I used a strong adjustment that would ordinarily clip the shadows and highlights severely, but since I don't have any of these tones in the selection I can use an extreme adjustment.

There is the opportunity for more subtle adjustment in this dialog compared to the saturation tool. I could change the shape of this curve, instead of leaving it straight, and I could adjust each of the individual color channels as well. This would allow for alterations in the color balance of the area at the same time if desired.

Curves Dialog
Curves Dialog
Notice the tree-shaped mask which is present in the top adjustment layer. This shows that this layer only affects the white portion of the masked image. Once again there is the opportunity to refine the mask using a variety of editing tools if the selection isn't exactly what is desired. One of the easiest is to reselect the mask (Control-click on the mask icon) and then switch to quick mask mode. This will show the mask in red. You can the edit it with the brush tools by selecting this channel from the channels palette.

This is another reason to keep adjustments on separate layers.

Curves Layers
Curves Layers
Here is the final version of the same image using the curves technique. I have exaggerated both the curves adjustment and the saturation adjustment so that the changes would be visible on a computer screen. The aim here is to produce the best quality printed image possible. The requirements for web viewing are not as strict.

Firstly, most people don't have their computer monitors adjusted properly. One has only to go into the local electronics store and look at the wall of TV displays to see how much variation there is between sets. Just as in photography, TV's and computer monitors generally come with the saturation, brightness and contrast turned up too high. Secondly, most images online are looked at in a small size and the subtle changes in detail won't be visible. The area I selected for this tip is less than one inch (25mm) in size in the final print.

Finally, most images online are looked at for only a few seconds, so spending a great deal of time getting them "just right" is wasted on the majority of your audience.

Curves Sample
Curves Sample
Below are both side by side for your comparison. Notice that the curves version also has brighter reds since these were included in the selected area. I could have done this with the saturation by also picking the red choice in the saturation dialog and boosting this as well.

What is more important is that the curves version has more "snap". Notice in the saturation version that the middle value greens have all lost their contrast. This is the problem with using the saturation tool. It works by subtracting black from the image. This makes the colors more saturated, but also lowers the mid-tone contrast and makes them look flat and unnatural. I would suggest restricting the use of the saturation tool to only those cases where there are bright colors without many details, such as at an amusement park or the like. Like many of the tools in Photoshop, the attempt to give people a quick and easy technique leads to an unsatisfactory final result.

Here's a link to the final image so you can see the sample in context. I also boosted the red tree as well. As I said, changes seen online are subtle, but the difference in an inkjet print is striking and worth the extra effort.

The reason to edit one's own images is to have the control over such subtle differences. It is this attention to detail that transforms the snapshot into an image to be proud of. Why spend much time and money on equipment and capturing the scene if it is all going to end up as a run-of-the-mill print?

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© 2008 Robert D Feinman