There are many sayings about seeing and believing or knowing. The three examples below are pertinent to our discussion here:
"Seeing is the key to knowing". This emphasises the importance of direct observation in determining what is real or true.
"Seeing is the touchstone of reality". This implies that seeing something first-hand is the ultimate measure of its reality or truth.
"To see it is to know it". This suggests that observing something personally provides a level of certainty that other forms of evidence may not.
What we are thinking about here concerns what you see on your computer screen when you look at an astronomical image that you or someone else has processed. Questions arise about the image:
If you have processed the image, will it look the same to someone else who is viewing it on their computer monitor not your own? Similarly, if someone else has processed an image on their computer will it look the same to you on your computer screen as it would if it is viewed on their computer screen; and, if not, why not?
Our three example sayings above are ultimately concerned with what you know when you look at something (in our case on a computer screen), and the question arises as to what you actually know if the object appears different (on a different computer screen).
How could the same image appear different on different computer screens? And if it does, which screen if any, is giving the correct presentation?
The answer of course is that the two monitors are calibrated differently and 'ay, there’s the rub', as Hamlet might say. Which monitor is showing an image that is closer to the truth?
There is no way of knowing unless the monitors are deliberately calibrated.
I refer the reader to a blog article that I published on 20 June 2021 entitled “Monitor calibration - Beauty is in the eye of the beholder”
The complete article can be seen Here
The current article is a sequel to the 2021 article.
The Importance of Using a Calibrated Monitor for Deep Sky Astronomical Imaging
When working with deep sky astronomical images, the precision and quality of your monitor’s display can make a world of difference. Not all monitors are equal and it is often the case that more expensive monitors come with better calibration than cheaper monitors. Laptop monitors have fewer controls that can be used to make adjustments but can still be calibrated.
Calibration produces an ICC profile for the monitor which is stored on the computer. According to the International Colour Consortium (ICC,) an ICC profile is a set of data that characterises a colour input or output device. The profile describes the colour attributes of a particular device. A device that displays colour can be assigned a profile, and this profile defines the colour gamut that will be displayed by this device.
How will an image prepared on a calibrated monitor appear on an uncalibrated monitor?
When viewing an image prepared on a calibrated monitor on an uncalibrated monitor, the differences can be quite noticeable. Here are some potential issues you might encounter:
1. Colour Accuracy: The colours might appear different, less vivid, or even distorted. For instance, subtle shades of nebulae might not be accurately represented.
2. Brightness and Contrast: The image could appear too bright or too dark. Details in both the shadows and highlights might be lost, affecting the overall quality and visibility of fine details.
3. Gamma: Differences in gamma settings can alter the way tones and mid tones are displayed. This can affect the smoothness of gradients and the overall balance of the image.
4. White Balance and colour temperature might shift, making the image appear warmer (more yellow/red) or cooler (more blue).
To ensure your deep sky images look their best across various devices, it is a good idea to make sure any critical viewing or sharing is done on calibrated monitors.
Calibrated monitors have:
1. More accurate Colour Representation
Deep sky images capture delicate details and variations in colour that are crucial for both scientific analysis and aesthetic appreciation. A calibrated monitor ensures that the colours you see on-screen are as true to the actual data as possible, allowing you to make precise adjustments without misinterpreting hues.
2. More consistent Brightness Levels
Calibration also stabilizes brightness levels across your display. For deep sky imaging, where faint stars and nebulae often blend into the dark background, having consistent brightness levels means you won't lose detail in the shadows or overexpose brighter areas.
3. More reliable Contrast and Tonal Gradients
Deep sky astronomical images feature a wide range of tonal gradients from the darkest regions to the brightest stars. A properly calibrated monitor maintains reliable contrast and tonal range, making it easier to distinguish between subtle differences in luminosity and structure within your images.
4. Professional Consistency
If you share your images with other astronomers, researchers, or even the general public, ensuring that everyone sees as near as possible, the same quality and details is crucial. Calibration provides professional consistency, allowing your work to be viewed more accurately across different devices and platforms.
5. Enhanced Post-Processing
Accurate colour representation, brightness, and contrast are vital for effective post-processing of astronomical images. A calibrated monitor ensures that your adjustments and enhancements are based on true data, leading to better final results without unintentional distortions or inaccuracies.
How to Calibrate a Monitor
Investing in a good hardware calibrator (which need not be overly expensive. The Datacolor Spyder at the time of writing can be obtained from the manufacturer for GBP 129) and using calibration software are the best ways to ensure your monitor displays accurate colours and brightness. Follow these steps for a basic calibration process:
Calibration is best done in a neutral lighting environment with minimal glare.
Use Calibration Hardware and Software: Devices like the Datacolor Spyder that we use, paired with calibration software, can guide you through the calibration process.
Recalibrate the monitor from time to time, as display characteristics can change over time.
In conclusion, a calibrated monitor is a necessity for anyone doing deep sky astronomical imaging. It ensures that the true intricacies of the deep sky are as accurately represented and analysed as possible.
Many professionals recommend embedding ICC profiles within your images to provide a more consistent viewing experience.
How to embed an ICC profile in an image using Gimp 2.10
Locate the ICC colour profile that the monitor calibration created. Copy it to a convenient location.
Follow the following workflow:
Image
Color Management
Assign Color Profile
Assign (search for and select the ICC profile that you placed in a convenient location)
Assign
The image now contains the ICC colour profile.
There is a plethora of display devices of wide-ranging quality that there is never a guarantee that what we see on our monitors will be the same as what is seen by others on their monitors, even if the above procedures have all been done; but if they have been done, we will be seeing closer representations of what the image producer intended than if they have not been done!
