What it does
Turns bright points into star glints with radiating rays and a hot glowing core, like a cross-screen filter on a lens.
The star filter is one of the oldest pieces of glamour kit in photography. A sheet of glass etched with fine parallel lines acts as a diffraction grating: point it at a concert stage or a candle-lit table and every light source grows a pair of rays perpendicular to the lines. Cross two sets of lines and you get four-point stars, three sets and you get six. Television variety shows and portrait studios of the sixties and seventies leaned on it so hard that the look became shorthand for showbiz sparkle.
Nature produces the same figure without the filter. The spikes on stars in telescope images are diffraction from the hardware in the light path, which is why stars from the James Webb telescope wear six prominent points, shaped by its hexagonal mirror segments, while Hubble’s wear four from the cross of struts holding its secondary mirror. Squint at a streetlight and your eyelashes will do it too. Any hard edge in front of a point of light splits it into rays, and the ray pattern is a signature of whatever produced it.
Recreated digitally, the effect starts where glow starts, with a brightness threshold that decides what counts as a light source, then streaks that light outward instead of blooming it evenly. Modulate’s Star Glow works in linear light, the same way its Glow does, so the rays fade like diffracted light rather than chalk lines drawn over the frame, and it can fringe them with color along their length the way real diffraction separates wavelengths. Ray count, rotation, and length set the character, from a single anamorphic streak to a dense starburst, and on video every glint flares and dies as the highlights underneath move.
Signature looks
Disco ball
Sequins, jewelry, and wet speculars throwing crisp four-point crosses across a dark frame. The variety-show sparkle the physical filter was invented for.
Anamorphic streak
One long horizontal ray through every light source, the widescreen lens-flare line of night-drive footage and music videos.
Telescope spikes
Fine six-point stars with rainbow fringing along the rays, points of light rendered the way a mirror telescope draws them.
Try it on your own footage
This effect runs live in the Modulate editor, with layers, effect chains, masks, and keyframes. Free, no signup, nothing to install.
Common questions
What is a star filter or cross-screen filter?
It is a physical filter that screws onto a camera lens, etched with a grid of fine lines that diffract light. Every strong highlight in the shot grows rays perpendicular to the lines, so a two-direction grid makes four-point stars and a three-direction grid makes six. The star glow effect reproduces the result digitally, without committing the whole shoot to the look.
Why do stars have spikes in telescope photos?
They are diffraction spikes, created by hardware in the telescope’s light path. The cross of struts holding Hubble’s secondary mirror draws four-point stars, and the hexagonal mirror segments of the James Webb telescope draw its signature six-point ones. The spikes are not part of the star; they are the telescope signing its own image.
What is the difference between glow and star glow?
Both begin the same way, by lifting everything above a brightness threshold, and differ in how they spread it. Glow blooms the light evenly in all directions into a soft halo; star glow streaks it along a handful of directions into rays. They also stack well: glow supplies the atmosphere, star glow supplies the sparkle on top.
Why do the rays show rainbow color fringing?
Diffraction bends long wavelengths more than short ones, so red light spreads further along each ray than blue. Through a physical star filter the rays grade from a white core to warm, rainbow-edged tips, and the digital effect reproduces this by letting each color channel fade at its own rate along the ray.
Can you add a star glow effect to video?
Yes, and video is where the effect earns its keep: the glints are recomputed from each frame’s highlights, so they flare up, stretch, and vanish as lights move through the shot, exactly like a filter on a lens. In Modulate, Star Glow runs live on images and video in the browser and stacks with Glow, grain, and color grades in the editor.
Related effects
Glow effect
Makes bright areas bloom with soft halos, like lights glowing through a hazy lens.
Lens blur
Blurs like a real camera lens, with out-of-focus highlights blooming into soft bokeh shapes.
Chromatic aberration
Splits the red, green, and blue channels slightly apart so edges fringe with color, like a photo taken through a misaligned lens.