Negative/de

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Negativbilder

Vielleicht arbeitest du bei deinen Aufnahmen noch immer mit analogem Filmmaterial. Oder du möchtest ältere Filme, die du eingescannt hast, bearbeiten. Meist handelt es sich dabei um sogenannte Negative. Bedeutet, helle Stellen im Bild werden dunkel wiedergegeben und dunkle Stellen hell. Bei Farbnegativfilmen kommt noch eine zusätzliche braun-orange Maskierung dazu und die Farben erscheinen auf den ersten Blick genau so negativ gemischt.

RawTherapee besitzt keine unmittelbare Ein-Klick-Unterstützung für Negativmaterial. Aus diesem Grund beschreibt diese Seite etwas ausführlicher, wie solche Bilder trotzdem mit RawTherapee bearbeitet werden können.

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Auf Grund der noch nicht übersetzen Seite "Filmsimulation", auf die hier immer wieder verwiesen wird, übersetze ich den folgen Abschnit noch nicht:

1. Invert a diagonal tone curve either in the Exposure tool, or all of the curves in the RGB Curves tool. In the Color Management tool select "No profile" as the input profile. The downside is that there are tonal shifts when doing this.
2. Use a negative Hald CLUT via the Film Simulation tool. The "RawTherapee Film Simulation Collection" contains one, get it from the Film Simulation page. The downside is that some controls might operate in reverse, such as the Exposure slider, and you may experience clipping in the shadows and/or highlights as these tools are not designed to work with negatives.
3. In addition to using the neutral negative Hald CLUT as described above, if you have a successful workflow of not only inverting negatives but also toning them to your liking in RawTherapee or in other software, you could make your own negative Hald CLUT which reproduces the whole look including negative inversion. To do that, apply the same steps to the "identity Hald CLUT image" shipped with the RawTherapee Film Simulation Collection as you would to a photo negative, save it under a new name, then open a photo negative in RawTherapee and apply that new Hald CLUT image. This lets you instantly achieve not only negative inversion but also your own toning with the click of a button, leaving you only needing to expand the histogram by adjusting the Exposure slider or using curves.
4. Currently the best method is to use the DCP (DNG Camera Profile) for your camera model but edited in DNG Profile Editor so that the diagonal tone curve is inverted, then manually loading this DCP in RawTherapee for all negative shots. Method outlined below.

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Ein DCP für Negative erstellen

Bildausschnitt des DNG Profil Editors mit der Tone Curve Registerkarte. Zeigt die diagonal invertierte Ton-Kurve für die Verwendung mit Negativen.

Die L* Kurve wird zur Behandlung eines Negativs mit einem negativen DCP verwendet. Die linke Spitze beruht auf dem Hintergrund um das eingescannte Foto, der das Foto ins absolute Schwarz gleiten lässt. Die rechte Spitze ist das eigentliche Foto des Scanns.

1. Lade dir den DNG Profile Editor herunter. Unter Linux arbeitet das Tool auch gut mittels wine.
2. Konvertiere eins deiner Fotos, egal ob aus der Kamera oder gescannt, zu DNG. Lies hierzu die Anleitung "Raw-Bilder zu DNG konvertieren".
3. Öffne das DNG-Bild im DNG Profile Editor
4. Prüfe in der Registerkarte Color, ob das Basisprofil "Adobe Standard ( <Dein Kameramodell> ) vorhanden ist. Wenn ja, wähle es aus. Wenn nein, wähle "Choose external profile" und suche das File mit der Bezeichnung "<your camera model> Adobe Standard.dcp". Die Anleitung "Wie werden LCP- und DCP-Profile erstellt?" erklärt, wie man zu diesem File kommt.

1. In the Tone Curve tab invert the diagonal so that it goes from top-left to bottom-right (move the top point to the bottom).
2. Still in the Tone Curve tab, there are three "Base Tone Curves" for you to choose from. "Base Profile" and "Camera Raw Default" are usually identical and have more contrast, while "Linear" makes the image look flat. We recommend you save one DCP which uses "Base Profile" and another which uses "Linear", and see for yourself which one better suits your needs in RawTherapee. Both DCPs will require further image tweaking in RawTherapee, but the "Linear" one will require more tweaking than the "Base Curve" one, though the latter might over-saturate colors - keep an eye on that.
3. To create the DCP, click "File > Export <your camera model> profile...". As recommended in the previous step, save two versions.

To use this new DCP for negatives, once you have your negative raw opened in RawTherapee go to the Color tab > Color Management section > Input Profile, and select Custom, then find this new DCP file. Enable "Use DCP's tone curve".

When tweaking images in RawTherapee using these DCPs, remember that using tone curves which operate on RGB channels (Tone Curve 1 and 2 in the Exposure tool) will change not only the lightness but also the color saturation the stronger your curves. You can control color saturation by using the "Weighted Standard" and "Saturation and Value Blending" modes, or you can avoid the problem by working in L*a*b* space. The advantage of working in L*a*b* space as the L* curve does is that colors are not changed while you modify the lightness, so you can fix the lightness first using as strong an L* curve as you need, and then fix the color saturation using for example the CC curve.