Difforum · Glow

The glow effect is one of the oldest and most reliable tricks in video: take the bright parts of the image, blur them, and screen-blend them back over the original. Result - the lights bleed, the highlights bloom, and a flat diffusion frame suddenly looks like neon at night. Difforum · Glow is that effect, distilled to four inputs and one IMAGE output, and it sits in the pack's VJ look group for a reason: it's the single cheapest way to add "expensive lighting" to a Deforum render or footage batch without a single diffusion step.

The three knobs do exactly what you'd hope:

• threshold (default 0.7, 0–1) - what counts as "bright." Only pixels above this get bloomed. Lower it and everything glows (soft, dreamy); raise it and only the true highlights bleed (neon signs, speculars).
• radius (default 8, 1–64) - how far the blur spreads. Small radius = tight halos; large radius = the whole bright area becomes a soft light source. This is the "how big is the glow" dial.
• intensity (default 0.6, 0–3) - how strongly the bloom is blended back in. 0.3–0.6 is tasteful; 2+ is full VJ overdrive.

Output: one image (IMAGE), works on a single still or a whole batch identically. In the Difforum pipeline it pairs beautifully with Colour Grade and Echo Trails: grade for a neon palette, let Glow bleed the lights, and Echo Trails drags the glow into motion smears. The difforum_vj_footage.json template is basically this group in one place.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/chillithebillis/Difforum.git difforum

Restart ComfyUI ([Difforum] loaded N nodes) or ComfyUI Manager → "Difforum". numpy-only, runs on CUDA/MPS/CPU automatically.

Common issues

• "The whole image goes hazy." threshold too low - you're blooming everything, including shadows. Raise it toward 0.7–0.85 and keep the glow on the highlights.
• "The glow is a hard-edged blob, not a bloom." radius too small for the effect to read as light. Bump it to 12–24; blur needs room.
• Not enough glow at max intensity. Check whether your source is already clipped to pure white - if the highlights are already at 1.0, there's no gradient left to bloom. Grade the exposure down slightly first.

It's a humble node, but it's the difference between a clip that looks generated and a clip that looks lit. Toss it after Colour Grade on any neon-themed render and you'll see what the pack's demo loops are doing - most of their "wow" is just this, executed well.