Same rendering gives different noise amount I usually render my single frame projects with the SheepIt-Renderfarm as animation of low-sample frames. But I experience great differences in the noise amount between some of the frames. For example, seed 5 (top) and seed 41 (bottom):




As you can see, one seed is way noisier than the other. There are several seed with less noisier result and the quality is always the same, like if some of my frames had been rendered with twice the samples.

Why are some seed noisier than others? How do I find out those? Is this even seed related?

I also tried the "split frame" function of the farm where each frame is rendered in 4 different tiles. [Imagine a rendering like the seed 41 one, but with seed 5 in the bottom left half of the picture - I'll add it later] There is the same effect, but on a single frame. So: same .blend file, same frame, same seed, different result. Why?
I'm not sure i have an explanation for that.

The faulty frames were rendered by two different users (5 for one user, 1 for the other), on different hardware (4 cpu, 2gpu). Only "windows" was the same but i don't know which version.

The Blender version used by SheepIt is actually the one from Blender Foundation, I just remove the blenderplayer.

Here are the binaries to verify, if that helps https://www.sheepit-renderfarm.com/media/binaries/

I'm also not modifying any seed value. Here is the python script I uss on a CPU render:

import bpy
bpy.context.user_preferences.system.compute_device_type = "NONE";
bpy.context.scene.cycles.device = "CPU";
bpy.context.user_preferences.system.compute_device =  "CPU";
bpy.context.scene.render.tile_x = 32;
bpy.context.scene.render.tile_y = 32