posts by upegelow

A new module for automatic perspective correction

Since many years darktable offers a versatile tool for manual perspective correction in the crop & rotate module [1]. Although the principle is simple and straightforward, there are cases where it can prove difficult to get a convincing correction, especially if no distinct vertical or horizontal features can be spotted in …

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Color Reconstruction

If you overexpose a photo with your digital camera you are in trouble. That’s what most photography related textbooks tell you – and it’s true. So you better pay close attention to your camera’s metering while shooting. However, what to do when the “bad thing” happened and you …

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Color Mapping

I’d like to give a few words on a new module named “color mapping” that is currently under development in our master branch. This module is a rework and enhancement of the older “color transfer” module. That older module had several issues which made a migration impossible. So we …

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Some enhancements to conditional blending

Conditional blending, also known as “blend if”, is a feature which is currently under development in our master branch. A general description of the idea together with some examples can be found here. In short, conditional blending allows you to limit the effect of a module to certain pixels of …

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darktable and Memory

or “How to drive away the evil skull”

At all times main memory was one of the most limited resources in computing. Although from 20 years to now the memory setup of a typical desktop PC has increased by a factor of several thousands (from less than a megabyte to …

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Upcoming features: Conditional Blending

or “If one slider is not enough”

Diligent readers of our small blog series are already aware of the blending feature that darktable offers as part of many modules. Instead of just handing over their result to the subsequent module in pixelpipe, “blending modules” take a moment to reconsider. Based …

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darktable and OpenCL (updated)

Many readers will have already heard about GPU processing and the fact that darktable can make use of OpenCL to improve performance. As we still lack a detailed documentation of that topic, please find here a few explanations and howtos.

The Background

Processing high resolution images belongs to the more …

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Shadow recovery revisited

One of the remaining shortcomings of digital cameras is their rather low dynamic range in comparison to analog – especially black-and-white – film. Scenes with strong differences between highlights and shadows are very difficult to capture. Even if they are exposed properly with no blown-out highlights they will too often only give …

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Using lowpass filter to recover shadows

Outdoor photographers are often confronted with unfavorable light conditions. This often entails too high contrast. Two of the most frequent consequences are blown highlights and deep shadows in your digital images. Overexposed highlights are challenging to repair in digital post post-processing, still darktable offers a decent set of valuable tools …

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Mastering color with Lab tone curves

or “How to bring the jungle back”

Since its early beginnings darktable has a tone curve module that is able to alter the gray level distribution of an image. Recently we did an enhancement: tone curve is now able to control the full Lab color space with separate curves for …

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