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Understanding Data Depths: Linear & Non-Linear Explorations in PixInsight

Faisal Khan

Tuesday, October 24, 2023

Imagine a night where you lay on the grass, eyes fixed on the vast canvas above, each star telling a story, each galaxy whispering secrets. Now, imagine capturing that magic, that story, in a frame. Sounds dreamy, right?

But the cosmos doesn't give up its secrets easily. Enter PixInsight, the magic wand that turns those raw, silent captures into eloquent tales of the universe. If you've ever felt lost amidst the stars or overwhelmed by the vastness of space, worry not.

Our comprehensive A to Z of PixInsight Masterclass series is your guiding star, ensuring you never lose your way in this cosmic journey. Dive in, and let's paint the universe together, one star at a time.

The Power of PixInsight: A First Glance

PixInsight isn't just another software, it's a universe in itself. With its intricate interface and myriad features, it promises to be the astrophotographer's best companion. Whether you're just starting out or have been capturing the stars for years, PixInsight offers tools tailored for all.

Decoding the Basics: Interface Layout and Common Windows

Welcome to the world of PixInsight, a realm where the universe's mysteries are just a click away. But before you embark on this cosmic journey, let's familiarize ourselves with the spacecraft's controls.

Decoding the Basics: Interface Layout and Common Windows

Menus and Toolbars

At the heart of PixInsight's interface lies its well-organized menus and toolbars. These are your gateways to the software's vast functionalities.

Whether you're a novice just starting out or a seasoned astrophotographer, these menus and toolbars are designed to be intuitive, ensuring that you can navigate through the software with ease. They act as the compass, guiding you through the myriad of features PixInsight has to offer.


Think of this as your cosmic canvas. It's where your images come to life, ready for editing and enhancement.

The workspace isn't just a passive display, it's an interactive space where you can zoom, pan, and get a closer look at the celestial wonders you're working on. Every pixel, every star, and every nebula is at your fingertips, waiting to be transformed.

Process Explorer

Your toolbox. From basic tweaks to advanced modifications, the Process Explorer houses tools that cater to every astrophotography need.

But it's more than just a collection of tools. It's a treasure trove of possibilities. Want to adjust the brightness levels of your image? There's a tool for that. Need to delve deeper into the histogram of your capture?

The Process Explorer has got you covered. Each tool is designed with precision, ensuring that you can bring out the best in your celestial captures.

PixInsight | Process Explorer | Kozmosi.io

The Science Behind the Image:
Understanding Linear vs. Nonlinear Images

PixInsight | Grayscale Tablet | Kozmosi.io

Grayscale Tablet Image

At the heart of understanding image processing lies the grayscale tablet image. Acting as a foundational tool, this 8-bit gradient seamlessly transitions from the darkest black to the purest white, offering a visual representation of discrete brightness levels within an 8-bit image.

8-bit vs. 16-bit: The difference in brightness levels between an 8-bit and a 16-bit image is staggering. While the former provides 256 distinct brightness levels, the latter, often used in astrophotography, boasts an impressive 64,000 brightness values. This vast range in a 16-bit image allows for capturing the intricate details of celestial bodies, making it a preferred choice for astronomers and astrophotographers.

The vertical bars in the image represent a scale value, the brightness, at each of these steps, the bars go from zero, which is black, all the way to white, which is 255, that is 256 values. In our image we have not separated out each of the 256 values, as we want to be able to visually see the step changes in brightness when we open the histogram tool.

The Histogram Transformation Tool

The Histogram Transformation Tool in PixInsight is more than just a graphical representation, it's your roadmap to image enhancement. By plotting the brightness levels of your image, it provides a visual guide, allowing you to adjust the image's shadows, highlights, and midtones.

Each vertical stripe in your image appears as a bar in both the input and output sections of the histogram tool. For instance, if you have 32 steps in your image, you'll see 32 bars in the histogram tool. This tool is essential for both beginners looking to understand the basics and experts aiming to refine their skills.

Brightness Levels and Their Manipulation

Every image has a range of brightness levels. In an 8-bit image, you have 256 levels, while a 16-bit image offers a whopping 64,000 brightness values. By adjusting the histogram, you can control these levels, effectively changing the ambiance of your image.

Whether you're aiming to highlight the darker regions or bring out the brighter areas, the histogram is your go-to tool. For instance, using the shadow clipping slider can move your blacks up a few brightness steps, turning them pure black, while adjusting the highlight clipping slider can make them pure white.

Linear to Nonlinear Transformation

This transformation is where the real magic happens. The midtone transfer function (MTF) curve in the histogram represents the relationship between brightness levels. By default, it's a diagonal line, indicating a linear relationship.

However, by manipulating the midtone slider, you can transform this linear relationship into a nonlinear one. This transformation is crucial in astrophotography, where you often want to bring out the faint details in the darker parts of the image, like nebulae and galaxies, while suppressing the brighter regions.

PixInsight | Histogram Transformation Tool | Kozmosi.io
Histogram Transformation Blacks | PixInsight | Kozmosi.io

Adjusting the midtone slider towards the blacks, for instance, expands the intervals in the darkest parts of your image, revealing more of the faint data.

Histogram Transformation Lights | PixInsight | Kozmosi.io

Conversely, moving it to the right suppresses the darker regions, highlighting the brighter areas. This nonlinear transformation is what allows you to bring out the finer details, enhancing the overall look and feel of your image.

Conclusion: Charting Your Cosmic Journey with PixInsight

Navigating the vast expanse of the cosmos through astrophotography is an art, and with PixInsight, it's an art that's within your grasp. But remember, every artist needs a guide, and that's where Kozmosi steps in.

We're not just a platform, we're your cosmic compass, illuminating the intricate pathways of image processing. Dive deep into our courses, and you'll find a universe of knowledge waiting to be explored.

From the basics to the advanced, every chapter is a step closer to mastering the A to Z of PixInsight. So, if you've ever dreamt of painting your own celestial masterpieces, now's the time. Join us at Kozmosi, and let's chart this stellar journey together.

Learn More

Expand your Astrophotography processing skills with Susie, the self-described "Angel Astronomer". Get the A to Z of PixInsight Masterclass membership and learn how to use PixInsight as a professional Astrophotographer.

Linear vs Non-Linear Data | PixInsight | Kozmosi.io