Robert D Feinman

More Effects with Curves

Scanning and digital capture leave many choices to the photographer. One of the most powerful ways to get the look you want is through the use of curves.

Here is a high contrast scene shot on color negative film and scanned so as to preserve all densities in the negative.

Notice the histogram shows that there is no clipping in either the shadows or highlights, but that much of brightness range is not being used.

Original Scan
Original Scan
Original Histogram Curve

One of the most common tools to use is the auto correct feature in either curves or levels. Here is the result with the maximize channel contrast. A sample channel is shown.

Notice that the curve is straight and that it cuts off at both ends. This expands the total range making the image look more contrasty, but the effect is still not pleasing. The tool is too inflexible.

auto clip
Auto Clip
auto clip histogram auto clip curve

Now we repeat the above step except this time we set the clipping points ourselves in just the RGB channel.

The lower values are a little darker and the highlights are not as washed out.

We will use this as the basis for further adjustments.

manual clip
Manual Clip
manual clip histogram manual clip curve

After  We have re-opened the curves dialog and added a control point in the shadow region. 

We have moved the curve downward in this region which has made the dark tones appear richer.

There is a small amount of clipping in the extreme shadows, but this is in areas of little interest.

lowered curve
Reduce Shadow Density
histogram lower shadows curve
We now add another control point to raise the mid-highlights.  This brightens the white rocks in the background as the sky slightly. s curve
Add S Shape
histogram s curve
Here is another variation. In this case we have only used a sharper S curve and not added any clipping at either end.

The effect is more colorful without any clipping. I would probably consider this my final version.
s curve
Stronger S Curve
histogram s curve
For those who like the punchy, colorful, high contrast look I've added to more adjustment layers.

The first is an saturation layer which increases the level by +17.

The second is a levels adjustment which restores some of the clipping seen in prior steps. This could be done with the curves as well, but when making levels adjustment it is possible to see which areas will be clipped during adjustment by holding the ALT key while moving the sliders.

By using curves we can create a variety of image looks. The automatic choices are fine for uncritical applications, but if you want to get just the effect you desire it pays to put in the extra effort. Other tools like levels are not as flexible. Mastering curves will take care of most of the contrast and brightness changes you might need.

Further fine tuning can be accomplished using masks to affect just certain regions of the image. See some of my other tips for examples.
Stronger S Curve with adjustments
histogram saturation

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© 2006 Robert D Feinman