EDIT THE NIGHT SKY
Remove grain and reduce noise in your imagery while retaining detail
When you’re shooting night landscape photographs, always make sure that your camera is capturing RAW images. RAW files will store a lot more data than JPGs, and you can quickly bring these details out using a camera RAW editor such as Adobe Photoshop or Lightroom.
Images captured with high ISO sensitivities will be more grainy than those captured with low ISO. When editing, you can reduce this noise to a point, but you begin to lose the finer details of the image if you go too far with the noise reduction. It is, therefore, better to try techniques that reduce or average out noise, such as longer exposures, or stacking exposures in Photoshop as layers with a blend mode of Lighten.
The better the dynamic range of your camera’s sensor, the more details you’ll be able to pull out in editing. A full-frame camera will perform better in low-light situations, although cameras with smaller sensors have caught up dramatically in the last few years.
The process of editing night-sky images varies massively according to taste. Some photographers like to really make the details of the Milky Way pop, others prefer a more natural look. Experimenting with settings such as Dehaze and Clarity will help you establish a style that you like. Two particular tools in Lightroom are useful, in that they enable you to edit only certain parts of the image. If you wanted to make an adjustment to the Milky Way, you can use the Adjustment Brush to ‘paint’ on edits to parts of the image. Then there’s the Graduated Filter, which will apply effects in a straight line.
1
LOAD IN YOUR SHOT
Working with Adobe Lightroom means that you can apply tags and keep your photos organised in folders. Also, in the Develop tab, all the tools you need to edit your image are in front of you in a focused work environment.
2
APPLY GLOBAL ADJUSTMENTS
At night, your camera isn’t great at gauging colour temperature. By shooting in RAW, you can adjust this to a more accurate level now. Adjust levels of Shadows, Highlights, Blacks and Whites, as well as Clarity and Saturation.
3
LOCAL ADJUSTMENTS
Once you are happy with edits across the whole of the image, you can begin working on specifics. Select the local adjustment brush and start painting. You can see where you’ve painted clearly by selecting Show Selected Mask Overlay.
4
GRADUATED FILTER
If you want to apply an edit in a graduated straight line, select the Graduated Filter tool, and click and drag on the image to show the area where the effect will be applied. This is particularly useful for shots with a defined horizon.
5
NOISE REDUCTION
Lightroom has a built-in noise reduction tool, which does a good job of getting rid of graininess in your high-ISO images. Selecting a value above 50 will result in a much cleaner image, but you smudge out the finer details in the shot.
6
STACKING
You can reduce the grain in high-ISO images by stacking multiple exposures as Lighten layers in Photoshop. For this sequence, the camera is on a motorised mount, which rotates at the same speed as the earth’s rotation, keeping the stars static.
7
REDUCTION IN GRAIN
By stacking longer exposures at lower ISOs, the amount of noise in the final image is tiny. With this technique the sky stays static but the foreground blurs, so you will need to load in a different shot of the foreground.
8
GOOGLE NIK COLLECTION
This collection is an add-on set of filters for Photoshop and Lightroom. Two particular tools are useful for astrophotography, if you want to seriously get into it. These are Tonal Contrast and Detail Extractor. You can see a comparison shot here.