| n | Number of camera samples per pixel |
| m | Number of photon passes |
| L ^ ( x, ω → ) | Estimated radiance at query point x in the outgoing direction ω → |
| L ^ i ( x, ω → ) | Accumulated radiance at query point x in the outgoing direction ω → until photon pass i |
| W ( x, ω → ) | Contribution of radiance L ^ ( x, ω → ) to pixel value |
| τ i ( x, ω → ) | Accumulated normalized flux until photon pass i |
| τ ^ i ( x, ω → ) | Normalized lux calculated using photons only from photon pass i |
| τ ˜ i ( x, ω → ) | Accumulated normalized flux after reducing kernel bandwidth |
| Ni | Total number of photons emitted from the first to the i-th photon pass |
| Ne | Number of photons emitted in one photon pass |
| K | Kernel function |
| k1 | Normalization constant of the kernel function |
| Ri | Kernel bandwidth at photon pass i |
| Qi | Number of photons within the kernel bandwidth Ri |
| tq | Normalized distance between hitpoint and photon q |
| ϕq | Energy of photon q |
| ϕ q f r ( x, ω → , ω → q ) | BRDF at hitpoint x from direction ω → to direction ω → q |