OTOY Forums

Hi all.

There was a post from ages ago by one of the Octane Team members that discussed how to use Octane resolution and Photoshop resolution to help reduce the effect of noise in images. It was something like render at twice the res you need, then drop it back to the lower value during post in Photoshop. Does anyone remember that post and where I can find it?

Many thanks!

Don't know what post you mean, but yes I have seen a few post mentioning this.
If you cannot get rid of noise after baking a while you can reduce noise by oversize rendering:
Let us say you want an image say 2000x1000px, you can render it i.e. 4000x2000px and afterwards resize it to 2000x1000px.
That works, I do it all the time.
Greetz,

Cool..Then I remembered it correctly.

Thanks rappet!!!

Hi treddie,

I also read this post and I think it was also mentioned to render an image twice or even more often and then combine the images in photoshop by multiplying or overlaying it in some other way... that will eliminate the noise, because the noise is random in every new render because of the GPUs way to calculating it.
Thats how I understood it, didn`t test yet, but seems to be logic.

Oversizing also is a quite good method, but it usually takes a bit longer to render, even if you need less max samples.

Greetings,
ChrisVis

Thanks, Chris!

I use that one a lot, myself. But am looking for a way to deal with those areas in scene that just aren't getting enough light, no matter how many renders I do, for compositing later. If I combine the two methods, I'm hoping I can drop the noise down another degree.

In postproduction you can also reduce noise by some function like 'remove noise' or something.
When I render oversize I reduce moise before and after resizing the render.
Greetz,

I've never been a fan of post-processing noise reduction methods for most work, only because they cause fine detail to get lost, like hairlines scratches on glass, or a fabric weave texture. I have not found any methods in Photoshop or NeatImage that can address that. Sometimes I get frustrated and say I'll just have to write my own filter. But it's a lot of work, and I'll have to get really annoyed first and snap in order to put the time aside to do it.

I just finished up some work that I will be posting soon, where I had to do it anyway. But when I did it in NeatImage, I put that filtered version as a layer over the noisy one, and only used the small parts in the upper layer that needed it, and erased the rest of the layer. But you can only go so far before it looks like blurry objects over an otherwise pristine image.

treddie wrote:I've never been a fan of post-processing noise reduction methods for most work, only because they cause fine detail to get lost, like hairlines scratches on glass, or a fabric weave texture. I have not found any methods in Photoshop or NeatImage that can address that. Sometimes I get frustrated and say I'll just have to write my own filter. But it's a lot of work, and I'll have to get really annoyed first and snap in order to put the time aside to do it.

I just finished up some work that I will be posting soon, where I had to do it anyway. But when I did it in NeatImage, I put that filtered version as a layer over the noisy one, and only used the small parts in the upper layer that needed it, and erased the rest of the layer. But you can only go so far before it looks like blurry objects over an otherwise pristine image.

Hi treddie,

I think you are right for really high detailed and high end still images. But lots of people here are doing animations and therefore noise reduction with plugins really is a great help and mostly good enough to use in professional work and save rendering time.
Your mask method in Photoshop is a quite good solution for stills but also timeconsuming, not practically for animation at all.

And as rappet said, it is better to use the noise reduction on the higher res image (because of more image data) before downsizing it.

I also get a little frustated with the noise. I have reworked a scene with lots of smaller light sources (about 30) that before had only 4-6 big light sources (used it last year with the C4D exporter and standalone). Now I compared both results with similar max samples and I see a lot more noise with the scene having 30 light sources in it. It helps a little to increase the sample rate of the individual light sources, but not enough to get noise free images faster.
This all is for animation, so noise reduction is the only way to go at the moment for me.

Greetings,
ChrisVis

Hi, I have found a method that can remove hot pixels efficiently. It doesn't work for heavy noise everywhere, though, and is only for still pictures.

Anyway I give it to you :

1 - in Photoshop or Gimp, or any image editing software using layers, put a copy of the same image on 3 layers. Use a denoise filter on the lower layer. Don't over do the filtering, but don't be afraid of getting a blurred image. The hot pixels are removed from this layer.

2 - Then, on the middle layer, select the hotpixels color with the magic wand. If necessary, increase the contrast or play with levels and threasholl to get only the hot pixels. Use this layer for selection only. Hide this layer.

3 - Once the selection is done, select the upper layer and hit suppression key. All hot pixels are erased and show through the color of the lower layer.

The image is not blurred, and the color of the nearest pixel is shown through holes leaved by the removed hot pixels.

But lots of people here are doing animations and therefore noise reduction with plugins really is a great help and mostly good enough to use in professional work and save rendering time.

I hadn't thought about that, but you're right. With everything moving around, the eye doesn't have time to concentrate on super fine detail for the most part. I don't do animations (not yet anyway), so I am stuck in that respect.

"... I have found a method that can remove hot pixels efficiently."

That is a cool solution! I'll give it a try. Thank you for sharing that."