DxO – Control Lines and Grad Filters

Is the Control Line in DxO PhotoLab 7 just a Graduated Filter with bells and whistles or is it more?

Control Lines and Grad Filters explained… Control Lines and Grad Filters in PhotoLab 7 are a binary choice, you use one or the other to do the job that can only otherwise be performed on camera, using a piece of smoked glass that balances out the light between the sky and the land.

The Control Line gives you a great many more options and is a much more powerful tool.

Video

This video provides an overview of these two types of local adjustment.

I have published a series of videos on PhotoLab 7 on YouTube, See DxO PhotoLab 7 Videos for the complete release schedule.

This video provides detail on how to control a Control line using Opacity, Chroma and Luma sliders.

Local Adjustments

DxO PhotoLab 7 uses masks to apply adjustments to areas of the image. There is a critical difference between generalised adjustments like contrast and exposure that change every pixel in the image, tone based adjustments like Selective Tone that work on areas of the image that are defined by tone and local adjustments that are applied locally, to areas of the image chosen by the photographer, regardless of tone or exposure.

DxO local adjustments are similar to layers in Adobe Lightroom in that they are easy to work with and quick to apply, but very powerful once you understand the potential.

Masks in PhotoLab 7

The first step in applying a local adjustment is to apply a mask. How this is done depends on the type of mask – DxO offer seven different types of mask in PhotoLab 7.

1. Control Point
2. Control Line
3. Graduated Filter
4. Luminosity Mask (If you have installed FilmPack 7)
5. AutoMask
6. Brush
7. Eraser.

DxO have designed the masks so that you can apply a set of common controls to the mask defined by the local adjustment.

Grad Filter in PhotoLab 7

The Graduated Filter is a digital representation of the old fashioned way of balancing light in a landscape. The problem faced by landscape photographers is that the difference between sky and land is often too great for digital sensors to balance properly.

This issue was originally solved by placing a sheet of smoked glass in front of the lens and adjusting it so the boundary sat roughly on the horizon. The solution worked well with seascapes and deserts, but not so well in the hills, where the horizon is jagged. Glass Filters still have a part to play in photography, check out Lee Filters for examples, but take a look at the video above to see a specific example of the problem that Grad Filters, glass or digital, are designed to address..

The Grad Filter is positioned on the image and applies a graduated filter to the image using that point as the start of the graduation or fall off. A second point is used to alter the rate of graduation and angle of the filter. Draw it away from the first point and the graduation will be more gradual. Position the first point to optimise the aesthetic effect on the image.

Other than the Common controls and the graduation/orientation control, the Grad Filter only offers an Opacity slider to finesse the intensity of the effect.

Opacity

This slider allows you to tune the impact of the effect up or down by blending it with the original image.

Control Line in PhotoLab 7

This is the reference image, slightly underexposed but requires shadows to be lifted in the framing rocks more than the sky. If we use the Exposure Control in the Light panel to do this, we end up with an overexposed sky.

The Control Line can be seen as a Grad Filter with bells and whistles. It is so much more powerful than the Grad Filter that I almost always go straight to the Control Line.

Opacity

Identical to the slider in the Grad Filter. It allows you to blend the effect wit the original image. Given the range of Selectivity tools, this is potentially much more exciting in the Control Line.

Selectivity

When you apply the mask to a sky, you typically drag it down from the top of the image to the horizon. This will apply a graduated filter to the sky, being more intense at the top and falling off as the sky meets the horizon. But what if there are mountains or buildings interrupting the skyline?

There are four ways that you can alter the areas affected by the mask.

Dropper

The dropper is placed by default adjacent to the positioning control of the control line. It samples the brightness and colour of the pixels it is placed on. You can drag the dropper to different areas of the image and that will control the reference point for the control line mask.

This next image shows the mask in black and white with the dropper left at the default location. The mask is the white/grey areas. you can see that it is slightly affecting the tops of the hills to right and left..

This next image shows the mask when the dropper is moved to a very bright location ie. the clouds. Note that the mask has “shrunk” leaving the mountains in the middle distance almost untouched compared to the previous image and the clouds much more clearly defined in the mask..

This next image shows the picture with exposure and highlights gently increased on the Control Line. Note that the mountains framing the sky and the middle of the image are virtually unmasked, because the dropper is placed in the brightest part of the sky.

Luma

The Luma control affects the sensitivity of the mask to the brightness of the area. By default it is set to 50%, the next image shows how much difference it makes when the mask is 100% tuned to the brightness of the pixels under the dropper.

Chroma

The Chroma control affects the sensitivity of the mask to the colour of the pixels covered by the dropper. This next picture shows that at 100% sensitivity the mask is much more tightly attuned to the blue of the dropper location.

Inverting the Mask

Shift – I inverts the mask, as shown in the next image.

This next image suggests that inverting the mask is a less complicated solution to this particular problem. Chroma and Luma adjustments have been made as in the black and white picture above.

The art of using local adjustments is to find the least complicated way of achieving your aim. There are other strategies that would also work to achieve this result, including dropping the dropper on the mountain so that the adjustment applies to the dark colours and luminance, or the use of negative masks.

Protecting Specific Areas

You can protect specific areas covered by a mask by placing a negative mask on the image. This will effectively erase the mask where the two masks overlap. Let’s say we wanted to protect the mountain on the right of the image, keeping it dark, while increasing the exposure on the left.

If we place a control line across the picture and drag it down to the horizon, it will cover both framing mountains so the addition of a couple of stops of exposure will affect both mountains equally.

If we add a negative control line to the right, only the mountain on the left is affected.

When using Negative Control lines, you must select the Control line you want the negative applied to.

Use the black and white mask to determine the exact scope and intensity of the mask. Opacity, Chroma and Luma adjustments are much clearer in this view.

Common Controls

The following common controls can be applied to masks, this gives us a great deal more flexibility when fine tuning or images.

• Exposure
• Selective Tone
• ClearView Plus
• Contrast
• White Balance
• HSL
• Sharpness
• Blur

Summing up Control Lines and Grad Filters

Control Lines are a much more powerful version of Grad filters.

Always use the Show Masks and B&W Mask to determine what is being masked and by how much.

Use Chroma and Luma controls to adjust the scope of the mask.

Use Inverted Masks for complex selections rather than creating extra masks whenever you can.

There are many ways to skin a cat! Lateral thinking is your friend, keep it simple.

Practice and patience are key!

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