Turning an ordinary night shot into a glow comes down to channel work plus colour layers. Convert to black and white to strip the original cast, pull the highlights out of a channel, then stack a purple Overlay layer and a cyan Color layer — get the order right and the effect appears. Do it in Online PS and you can shift the palette to taste.
Step 1: Convert the image to black and white (remove the original cast)
The colours already in the photo decide what the glow will look like. Converting to black and white first makes the light effect cleaner and the colour far easier to control.
- Open Online PS, import the night shot and choose Image → Adjustments → Black & White (Ctrl+Alt+Shift+B).
- In the Black & White dialog you can tune the brightness of each channel — the defaults are fine to start with.
- If you want to keep the original layer intact, use a Black & White adjustment layer (Layer → New Adjustment Layer → Black & White). That way you can always back out.
Step 2: Extract the highlights (channel selection)
Next we need the bright areas — the highlights — isolated, so the glow colour can be painted into them.
- Open the Channels panel (it sits on the right by default; if it is hidden, tick it under Window → Channels).
- Hold Ctrl + Shift and click the channels you want — you can click several — and the system merges their content into a single selection.
- The usual approach is to take the highlights of RGB, Red and Green (the brighter regions). If the frame is generally dark, RGB alone is enough.
- Once the selection is made, go back to the Layers panel and add a blank layer (Ctrl+Shift+N) — anything you fill will land inside the selection only.
Step 3: Add the purple layer (blending mode: Overlay)
Fill the selection you just made with a highly saturated purple; that gives the glow its warm-cool contrast.
- Make sure the blank layer you created still has the selection active.
- Take the Fill tool (G) and set the foreground colour to
#8A2BE2— or pick a more saturated purple yourself. - Click once anywhere on the canvas to fill the selection with purple.
- Then set the layer's blending mode to Overlay. There is no need to touch Opacity; leave it at 100%.
- Deselect (Ctrl+D) and the purple light spreads a soft glow across the night scene.
Step 4: Add the cyan layer (blending mode: Color)
Fill the same selection — or re-select the highlights — with cyan to enrich the cool light.
- Hold Ctrl+Shift and click the same channels to rebuild the selection (or simply Ctrl+J the previous layer and fill that).
- Add a blank layer (Ctrl+Shift+N) and name it “Cyan glow”.
- Set the foreground colour to cyan, for example
#00CED1(bright cyan), and fill the canvas with the Fill tool. - Set the blending mode to Color and leave the opacity alone.
- Deselect and you will see the cyan shift only the hue of the bright areas while their brightness stays exactly as it was.
Step 5: Reorder the layers (cyan below purple)
The purple layer uses Overlay and the cyan layer uses Color. They behave differently, and the wrong order leaves the whole frame looking cyan.
- In the Layers panel, drag the “Cyan glow” layer below the “Purple overlay” layer.
- Now Overlay only strengthens the highlights, while Color shifts the hue of what sits beneath it (the purple layer), so the two blend far more naturally.
- If the overall tone reads too warm or too cool, adjust the opacity of both layers — 70%–90% is the usual sweet spot.
Step 6: Fine-tune & export
The effect is basically there. Adjust it as needed, then export.
- Add Gaussian Blur to the “Purple overlay” layer (Filter → Blur → Gaussian Blur) to soften the glow.
- Use Hue/Saturation on the “Cyan glow” layer (Image → Adjustments → Hue/Saturation) to tune how deep the colour goes.
- For a starlit feel, add another blank layer above both, then use the Brush (hardness 0%) to dab a few small stars over the highlights. Set that layer to Screen.
- When it is done, File → Export As → PNG/JPEG (Ctrl+Alt+Shift+S) saves it.
References
- Online PS
- Adobe official documentation
- Photoshop tutorial sites