Bloom (render effect)
A post-processing effect that makes very bright areas of an image glow softly into nearby pixels.
Why jewelry renders use it
Diamonds and polished metal produce tiny, intense highlights. On a screen those highlights are limited to plain white pixels, which can look flat. A gentle bloom adds a slight glow around the brightest points, which reads as sparkle and gives a photographic feel.
How much is enough
Bloom is easy to overdo. Strong bloom turns a field of pavé into a haze, blurs prong edges and makes white metal look foggy. A good test is a close-up of small stones. If you can no longer count them, the bloom is too strong.
Bloom versus real sparkle
Bloom does not create fire or scintillation. Those come from the stone's geometry, the gem material and the lighting. Bloom only changes how the brightest pixels are shown, so get the gem material and environment right first and treat bloom as finishing.
In practice
The RenderMyJewels studio applies a gentle bloom by default, so pinpoint highlights on stones register on screen without washing out detail. Whatever renderer you use, keep bloom subtle for product pages, where buyers zoom in, and save stronger glows for mood pieces such as social posts.