final version of the sunset over the Douro River
original version of the sunset over the Douro River

At first glance, the exposure module might seem quite basic. However, this module combined with darktable's powerful masking features can be used for a wide variety of purposes; let's explore these below.

Exposing The Midtones

final version of the ornate stone hallway
original version of ornate stone hallway

The basic usage of exposure, as outlined in The Darktable Scene-Referred Workflow, is to properly expose the midtones of the photo. Once this is done, you can use a tone mapping module (like filmic rgb or sigmoid) to adjust the shadows and highlights.

When you first activate the exposure module, you may notice that it starts off at a non-zero value (e.g. +0.700 EV). As described in this thread, this is done to brighten the RAW file to be closer to what the out-of-camera JPEG looked like (since your camera is applying a base curve automatically when creating the JPEG).

The RAW file for the above photo is pretty dark due to the direct sunlight on parts of the stone pillars (we need to avoid clipping these when capturing the image). Therefore, use exposure to raise the exposure of the image so that the hallway looks good:

hallway exposure module

Next, pull down the white relative exposure slider in filmic rgb to avoid overexposing the parts in direct sunlight:

hallway filmic rgb module

Often times this is sufficient, but if you have a very high dynamic range, such as in this photo, an instance of tone equalizer with just the highlights pulled down can also help:

hallway tone equalizer module

Dodge and Burn

final version of the Abe Lincoln statue with face dodged
original version of the Abe Lincoln statue

One of my favorite uses for exposure is to make targeted adjustments, such as brightening up a face that is shaded. The key is to use the feathering radius slider along with the mask contrast slider when creating the mask to ensure the effect clings just to the face and doesn't result in a circular bright spot (which would look like an obvious distortion):

face exposure module

Because of the power of darktable's masks, this is fast, easy, and highly effective. This effect is more subtle than some of the others, but it can really help bright up an underexposed face or area of focus.

Vignettes

final version of the red lighthouse with a vignette applied
original version of red lighthouse

While darktable has a vignette module, I often find that it's easier to use a drawn mask on an instance of the exposure module, invert the mask, and create a vignette. This allows me to easily and precisely control the size and shape of the vignette and where it is placed. In this example, the vignette helps darken the background and highlight the lighthouse:

lighthouse exposure module

Simulating a GND or Changing Dynamic Range

final version of the sunset over the Douro River
original version of the sunset over the Douro River

As described in the post on GNDs, you can compress the dynamic range of a scene using a Graduated Neutral Density filter in front of your lens. However, if you don't have a GND with you, and you can avoid clipping with the dynamic range of your camera, you can simulate a GND in post using an instance of the exposure module and a gradient mask:

gnd exposure module

As with a physical GND, this works best where the transition between the two dynamic ranges is straight, such as a horizon.

An alternative way to reduce the dynamic range on a scene like this is to use tone equalizer. This has the advantage of being able to handle edges which aren't straight, but also may introduce an unnatural look if pushed too far. In this scene, tone equalizer is better for adjusting the sky and preserving the relative contrast between the clouds and sky itself:

gnd tone equalizer module

Finally, use the colorize module with a drawn mask and the overlay blend mode to add some blue to the river to give it more depth:

gnd colorize module

Adding a Light Source

final version of the Arashiyama bamboo grove with path highlighted
original version of the Arashiyama bamboo grove

You can also use the exposure module to add a light source that was missing in the original image. There are limitations to this technique, but it can still be a powerful way to alter the look of a photo. In this example, we have bright light filtering through the bamboo, but also want to highlight the path through the grove. Therefore, use a drawn mask and an instance of the exposure module to brighten the path, as if we were shining a bright light down upon it:

bamboo exposure module

Conclusion

The humble exposure module is one of the most essential modules in darktable. Combining multiple instances of this module with masks allowed you to selectively dodge and burn parts of the image, add a vignette, adjust the exposure of the global midtones, and so much more.


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