How to Add Tyndall Light Through a Window in Photoshop

Adding Tyndall light to a window follows a fixed recipe: select the light source with the Quick Selection tool, copy it to a new layer, stretch it into beams with Radial Blur, then blend with Screen. The critical part is landing the blur center on the light source — otherwise the rays scatter.

Before you start

Open Online PS (https://www.zaixianps.cc).
Have a photo with a window ready (a scene where light streams in from outside works best).
If you want a more precise light-source selection, turn on the Quick Selection tool (W) in Online PS.

Full walkthrough

01 Step 1: Load the image in Online PS

① Click File in the top-left → Open, or just drag the image into the browser window.

② Check that the image now appears in the main workspace.

02 Step 2: Select the highlight (light source) area with the Quick Selection tool

① Pick the Quick Selection tool (W) from the toolbar on the left.

② Click or drag once on the canvas and try to select the whole bright highlight inside the window — the brightest patch of light.

③ If the selection is not precise enough, hold ⌘/Ctrl + Alt to switch to Subtract or Add for part of it.

03 Step 3: Copy the selection to a new layer (Layer 1)

① When the selection is ready, right-click it → Layer via Copy, or press Ctrl+J.

② The new layer is named “Layer 1” automatically and holds only the highlight part of the light source.

04 Step 4: Apply the Radial Blur filter to Layer 1

① Make sure “Layer 1” is selected.

② Menu bar → Filter → Blur → Radial Blur… (Filter → Blur → Radial Blur).

③ In the dialog that opens, use these settings:

Blur Method: Spin (Radial) or Zoom; Zoom is recommended.
Amount: usually between 30–80, adjusted to how long you want the rays.
Blur Center: drag the icon or type coordinates so it sits on the emission point of the light (usually the light source outside the window).
Preview the effect and click “OK” when you are happy with it.

05 Step 5: Set the layer blending mode to “Screen”

① Find the “Normal” drop-down at the top of the Layers panel.

② Switch the blending mode to “Screen” (Screen). The light then blends naturally over the background — brighter, while the underlying detail survives.

06 Step 6: Fine-tune (re-apply the filter as needed)

If the beams still look unnatural, too weak or too hard-edged, repeat the Radial Blur from step 4.

Shortcut: Alt+Ctrl+F (in Photoshop this re-applies the last filter). Check the result after each application.

If necessary, lower the opacity of “Layer 1” (say 70%), or give the layer a Soft Light/Overlay blending mode for a second pass.

Export the result

When you are done, save with File → Export As → PNG or JPG. If you still plan to color-grade later, keep a PSD (.psd) file so you can keep editing.

References

Adobe Photoshop official documentation
HTML5 and the principles of modern front-end image processing
Online PS