I created Christmas tree using this tutorial (http://www.blenderguru.com/tutorials/how-to-make-a-christmas-tree/). In a words it uses Sapling Add-on(3-level tree) and Hair particle system using 900k emission number, and shaded with this node scheme:

Then I created simple "Rotation" keyframes, which rotates camera around the tree, but from frame to frame the noise looks like its blinking, here is the first 10 frames animated in gif:

What is wrong?

• It could be just animated "noise". Is that present in the single images? What happens if you raise the sample number till getting rid of it? Does the flickering persist? – Carlo Dec 13 '15 at 13:32
• Isn't that noise for not having enough samples? – Samir Rahamtalla Dec 13 '15 at 13:32
• Can you post your sample settings and your noise seed? Try setting your samples way up (a few hundreds) and see if this helps. – Samoth Dec 13 '15 at 13:45
• Yes, increasing samples solved problem! Thanks very much! – Ivan Borshchov Dec 13 '15 at 13:53
• Consider the option to write and mark as accepted an answer to your own question, maybe showing the difference bewteen the results after changing the number of samples – Carlo Dec 13 '15 at 16:10

Thanks for all comments, the reason was in rendering noise. By default it was only 10 Samples for render (Properties -> Render -> Sampling -> Samples -> Render), Now I use 200 samples and Hair particular System looks perfect! But after changing this option each frame rendering time increased in several times, so you should not increase Samples count too much.