Screen Calibration for Astrophotography
With my recent purchase of a new laptop computer, I am reminded of the importance of having a well calibrated computer monitor for editing and viewing astrophotos. The brightness of my new laptop screen is intense. It appears to be about 25% brighter than my well-calibrated 23 Inch external IPS monitor. This results in astrophotography images that are less-than pleasing to the eye. I had to re-process many of my own photos in the photo gallery, once I discovered that they did not look the way I intended them to on different screens.
Having a monitor that is too bright will show all of the impurities in your background sky.
If you have been processing your astrophotography images on a dim monitor, you may be in for an unpleasant surprise when you see them on a bright screen for the first time! When you upload your image to the web, you have to accept the fact that people from all over the world may view your work on monitors and screens that display images MUCH different than yours. It is wise to make sure your computer screen is giving you an accurate rendition of the image you worked so hard to capture.
Why should you calibrate your monitor?
Screen calibration helps to ensure that colors are represented accurately on your monitor. This is an important aspect of your experience on the computer whether you are processing astrophotography images or not. You will ensure that you are seeing the images displayed on screen as they were intended to be viewed. This is especially important for creative professionals such as Graphic Designers, Photographers and Video Production teams. The idea is to have your monitor conforming to a preset color benchmark such as the sRGB or Adobe RGB color space.
How to Calibrate your Screen for Astrophotography
The first step towards adjusting your computer monitor display settings is by using the interface on the unit itself. Some models have more in-built control options than others. If you use an external monitor like me, it will have a set of controls, usually at the front and under the screen. My ViewSonic LED monitor has the typical bare bones contrast, brightness, and color mode. Make sure that you do not have any ambient lighting in the room affecting your views. Do not calibrate your monitor in a bright, sunlit room, or with reflections appearing on-screen.
For accurate results, face your screen head-on, with your eye lined up with the top of the screen.
Calibration Tools and Adjustments
It is necessary to have some reference material on-screen that will let you know if you’ve pushed your settings too far one way or the other. See the grayscale chart from APCmag below:
Using the Color Calibration Feature in Windows 10
If you are using Windows 10, they have a nifty color calibration walk-through that is great for making adjustments called Display Color Calibration. It will take you through a number of tests to see just how far off your display is. They call it “color” calibration, but it’s really an overall screen calibration test. You can get to it by following this command path: Start Menu > Settings > System > Display > Advance Display Settings > Color Calibration. The following calibration images are used in the Windows color calibration test.
Have you Checked Your Gamma Today?
“Gamma defines the mathematical relationship between the red, green, and blue color values that are sent to the display and the amount of light that’s ultimately emitted from it.”
In the image above, you should not see any overly obvious “dots” within the circles.
The Brightness Effect
As I stated earlier, having a display that is too bright can absolutely wreak havoc on an astrophoto that has been stretched too far. I know about this phenomenon all too well, as I like to stretch my data to the max. The tell-tale signs of an astronomical image that has been stretched too far, or with serious gradient and vignetting issues – is a muddy, green/brown background sky. The sky may appear to have a nice neutral dark grey or black on your dim monitor, but on your nephews brand new ultra-backlit iPhone, it’s a multicolored mess! Even images on APOD can appear to diminish in quality under the scrutiny of an overly bright display.
Here’s an image you can use as a guide. You should be able to distinguish between the mans shirt, and the background. The black “X” in the background should be barely visible.
Contrast – Don’t Overdo it
Using the image below, adjust the contrast settings of your monitor so that the background appears black and not grey. If you have lost details in the white shirt the man is wearing, such as the buttons and creases, you have pushed the contrast too far.
My Best Advice
My advice is to process the image on image on a screen that has been calibrated as best as possible. If you have access to a overly bright, unforgiving display – maybe have a look at your image on that as well. It can be useful to see an exaggerated version of your subject, and fix any issues that really jump out at you.
My Main Astrophotography Monitor for Processing:
Take a look a few example astronomy photos taken by professionals on Astronomy Picture of the Day. Use the color, levels and background sky you see in their photos as a guideline. Chances are, the photos you see here will look great, no matter which display screen you view them on. This is because they have taken the precautions needed to ensure that their images are an accurate representation of scientific data, including screen calibration. Many of these astrophotographers have dedicated calibration tools to help them keep their displays accurate.
I have had many issues with uneven sky backgrounds in the past, probably due to lack of flat frames or poor quality flats! The dim monitors hide this messy background making the sky to appear a nice dark grey or black. There is value in viewing your images on a variety on screens to learn how to better process your images. I hope that this write-up has opened your eyes to the importance of screen calibration when processing astrophotography images. As for getting your night sky photos printed? I’ll save that for another post;)