Noise reduction by averaging pictures

[SilentPrayerCG]

Hi.

I did an experiment.

Digital noise seems never completely disappear from the picture.

I leave render at all night, but noise still be here. (it is not very bad, and i think it common for all unbiased renders)

After some time of rendering noise reduction becoming smaller and smaller.

Yesterday i found this article http://www.cambridgeincolour.com/tutorials/image-averaging-noise.htm

I wrote some program (i know it can be done in photoshop, but i like automatize processes)

I render 5 images (445 passes per image, approximately 40min on my phenom x6 with legacy corona) by BDPT engine, with different seed

and averaged them

There is result:
1) one of original image
https://dl.dropboxusercontent.com/u/12629675/egg/egg_or.png

-------------

2) 5 images mixed by averaging
https://dl.dropboxusercontent.com/u/12629675/egg/egg_aver.png

-------------

3) difference sample
https://dl.dropboxusercontent.com/u/12629675/egg/egg_difsamp.jpg

[Ondra]

averaging images like this is exactly what happens internally. If you average 5 images with different seed, you will get the same image as if you would render for 5 times longer.

UNLESS....

you average images with gamma on. This is wrong and produces incorrect image (and I think that is what happened - your averaged image is darker). Then you will get biased results, but probably with less noise. This is very similar to vray subpixel mapping on.

[SilentPrayerCG]

averaging images like this is exactly what happens internally. If you average 5 images with different seed, you will get the same image as if you would render for 5 times longer.

UNLESS....

you average images with gamma on. This is wrong and produces incorrect image (and I think that is what happened - your averaged image is darker). Then you will get biased results, but probably with less noise. This is very similar to vray subpixel mapping on.

I didn't notice it is darken...(maybe because it is day, maybe in dark room it will be most notable). I just save images form framebuffer, gamma in 2.2 as default, i not touch it for corona render
Anyway, i expected it, i wanted to render test image for 5 times longer, but you already explain all

Well, i just wanted to make something, fail it will be or not.

Txh for explanations Keymaster.

ps

atleast i can use my program for reduce noise from photo... if only i had tripod and remote for camera..

[romullus]

atleast i can use my program for reduce noise from photo... if only i had tripod and remote for camera..

You can make bean bag at no cost and practically all cameras has self timer, so... there's nothing you can't do.

[SilentPrayerCG]

atleast i can use my program for reduce noise from photo... if only i had tripod and remote for camera..

You can make bean bag at no cost and practically all cameras has self timer, so... there's nothing you can't do.

no, camera still will be move a little when i push button.

i already tried it. i put camera on table and use continuous shooting option, pictures had a difference.

[Ondra]

most cameras I saw had autotimer that enabled sequences...

[SilentPrayerCG]

most cameras I saw had autotimer that enabled sequences...

my old one, i didnt saw such option

[romullus]

no, camera still will be move a little when i push button.

i already tried it. i put camera on table and use continuous shooting option, pictures had a difference.

If you own photoshop, then it could be easily aligned. I'm not sure if photos still would be applicable for noise averaging, though. OTOH, pictures shot at base ISO and long shutter speed gives almost as good results as averaging from multiple shorter exposures.

[SilentPrayerCG]

no, camera still will be move a little when i push button.

i already tried it. i put camera on table and use continuous shooting option, pictures had a difference.

If you own photoshop, then it could be easily aligned. I'm not sure if photos still would be applicable for noise averaging, though. OTOH, pictures shot at base ISO and long shutter speed gives almost as good results as averaging from multiple shorter exposures.

i still need tripod if i want shoot something... not random shit at home.
i dont think i can merge photos with offsets

nevermind, for photography need get out of home (may be go on nature) and it need do, being not alone. (especially in my city). I dont have such opportunity.