Darktable on PIXLS.US

Darktable 3:RGB or Lab? Which Modules? Help!

Sun, 26 Jan 2020 00:00:00 +0000

Original post in French by Aurélien PIERRE , edited by the pixls community.

Darktable is slowly converging to a scene-referred RGB workflow. Why is that? What does it involve? How does the use of darktable change? Answers here…

This article begins with a 3 section introduction of the Lab space. You don’t need to understand it in detail in order to understand what happens next.

What is Lab?

The color space CIE Lab was published in 1976 by the International Commission on Illumination (CIE), in an attempt to mathematically describe the color perception of the average human being. Lab space aims to decouple the brightness information (L channel) from the chroma information (channels a and b) and takes into account the non-linear corrections that the human brain makes to the linear signal it receives from the retina. Lab space is derived from CIE XYZ space , which represents the physiological response of 3 of the 4 types of photo-sensitive cells in the retina (the cones).

Create lens calibration data for lensfun

Thu, 15 Nov 2018 08:00:00 -0500

[Article updated on: 2019-12-09]

Introduction

All photographic lenses have several types of errors. Three of them can be corrected by software almost losslessly: distortion , transverse chromatic aberration (TCA) , and vignetting . The Lensfun library provides code to do these corrections. Lensfun is not used by the photographer directly. Instead, it is used by a photo raw development software such as darktable or RawTherapee. For example, if you import a RAW into darktable, darktable detects the lens model, focal length, aperture and focal distance used for the picture, and it then calls Lensfun to automatically correct the photograph.

Profiling a camera with darktable-chart

Wed, 25 Apr 2018 19:00:07 -0500

[Article updated on: 2019-06-18]

What is a camera profile?

A camera profile is often a combination of a color lookup table (LUT) and a tone curve which is applied to a RAW file to get a developed image. It translates the colors that a camera captures into the colors they should look like. If you shoot in RAW and JPEG at the same time, the JPEG file is already a developed picture. Your camera can do color corrections to the data it gets from the sensor when developing a picture. In other words, if a certain camera tends to turn blue into turquoise, the manufacturers internal profile will correct for the color shift and convert those turquoise values back to their proper hue.

How to create camera noise profiles for darktable

Sun, 15 Apr 2018 19:00:07 -0500

[Article updated on: 2019-11-26]

What is noise?

Noise in digital images is similar to film grain in analogue photography. In digital cameras, noise is either created by the amplification of digital signals or heat produced by the sensor. It appears as random, colored speckles on an otherwise smooth surface and can significantly degrade image quality.

Noise is always present, and if it gets too pronounced, it detracts from the image and needs to be mitigated. Removing noise can decrease image quality or sharpness. There are different algorithms to reduce noise, but the best option is if having profiles for a camera to understand the noise patterns a camera model produces.

A Q&A with Photographer Riley Brandt

Wed, 15 Jul 2015 08:47:30 -0500

Riley Brandt is a full-time photographer (and sometimes videographer) at the University of Calgary . He previously worked for the weekly (Calgary) local magazine Fast Forward Weekly (FFWD) as well as Sophia Models International , and his work has been published in many places from the Wall Street Journal to Der Spiegel (and more ).

He recently announced the availability of The Open Source Photography Course . It’s a full photographic workflow course using only free, open source software that he has spent the last ten months putting together.

Luminosity Masking in darktable

Tue, 06 Jan 2015 13:41:08 -0500

Luminosity Masking, the ability to create selections of your image based on its specific tones for ultra-targeted editing, is a relatively recent concept favoured by landscape photographers the world over. In this article, we will explore how to create and use Luminosity Masks in the F/OSS RAW editor darktable , so that you can make adjustments on your RAW files to isolated tones.

What is Luminosity Masking?

Luminosity Masking is a technique developed in the last 10 years or so primarily by American Southwest landscape photographer Tony Kuyper over at goodlight.us . Tony provides extensive writing and information on Luminosity Masking and how to create Luminosity Masks; in this article I’ll be primarily focusing and creating and using the masks in darktable, but if you want to really understand the basics I highly recommend giving Tony’s guide a good read over first.