Lowpass, Highpass and how I use them

What is the difference between Darktable’s overlay and softlight blend modes?

Overlay adds contrast and softlight is a more gentle version. In this video tutorial I dive deeper into the questions I get asked most often about how I utilize Darktable's lowpass and highpass modules. I show different effects realized by combining them with overlay and softlight blend modes.

After the discussion and examples, I get to edit a contributor's RAW file. Thanks Sergei for the beautiful shot to work with.

Here is the link to the Darktable.org blog post "Using lowpass filter to recover shadows"

The RAW files used in this video are available here
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9 thoughts on “Lowpass, Highpass and how I use them

    • Aloha Mathieu,

      The lowpass, shadows/highlights, and equalizer all use similar methods. So you’re right about them being similar. But I find the lowpass method easier to visualize where the effects are happen. Also it’s gives a little separation with defocusing some elements vs others. But sometimes I don’t want that effect and I’ll use the shadows/highlights or equalizer. This would be a great idea for a video topic, comparing the effects of each.

      Thank you so much for writing,

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  2. I’ve created some notes based on this video and I’m sharing below to help others.

    “Overlay adds contrast and softlight is a more gentle version.”

    Overlay takes more effect in the mid tones (specially between the mid tones and the light tones, and between the mid tones and dark tones).
    Softlight protects the light and dark tones, taking effect on the mid tones.

    – Lowpass Filter

    – Recover Shadows (darker parts -> brither / lighter parts -> darker):
    – Overlay
    – Radius: any (control the transition zone)
    – Contrast: negative (control the effect)
    – Brightness: 0
    – Saturation: 0

    – Apply tones (more 3D look, less flat / shades more continuous):
    – Softlight
    – Radius: any (less -> sharper / more -> more continuous transitions) (adjust just enough to see the wanted details)
    – Contrast: positive (control the effect)
    – Brightness: 0
    – Saturation: 0

    – Separate things (more contrast / separate from background):
    – Overlay
    – Radius: any (adjust to large enough to see general only the shape of objects)
    – Contrast: 1
    – Brightness: 0
    – Saturation: 0

    – Highpass Filter

    – Apply tones (same as lowpass, but works on fine grain details / bring out fine details):
    – Softlight
    – Sharpness: 100% or lower
    – Contrat boost: any (control the shade)
    – Opacity: control the effect / remove hallos in the edges
    – Parametric mask: more effect on highlights

    – Sharpen edges:
    – Overlay
    – Sharpness: any (adjust to low enough to see only the edges of objects)
    – Contrat boost: any (same as Sharpness)
    – Opacity: control the effect

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