noise understanding

[meris]

I want to check my understanding of

http://www.damiensymonds.net/tut_noise.html

 

So you are adding monochrome noise to artificial gradients. It's random noise, but in repeating blocks of 80×80. Is there a reason for 80, not bigger?

Is there any situation where you'd add this noise to natural bg?

 

Then looking at

http://www.damiensymonds.net/2010/07/raw-noise-removal.html

looking at a plain grey area and upping the luminance noise setting, I was at 88 to get it clean. This was a D800 file with ISO200. At these settings it was hard to tell if it was noise in the image, or the reflection of the screen surface, or spots in my eyes.

color was at 50, again I wasn't sure if there were just bright spots in my eyes but I needed it that high in plain areas.

Does it sound right or did I mess up?

 

In this case, should I add the noise above to the cleaned up image?

[Damien Symonds]

2 minutes ago, meris said:

So you are adding monochrome noise to artificial gradients. It's random noise, but in repeating blocks of 80×80. Is there a reason for 80, not bigger?

I don't know the reason.  That's just a size that Adobe like.

2 minutes ago, meris said:

Is there any situation where you'd add this noise to natural bg?

I can't think of a reason, no.

2 minutes ago, meris said:

looking at a plain grey area and upping the luminance noise setting, I was at 88 to get it clean. This was a D800 file with ISO200. At these settings it was hard to tell if it was noise in the image, or the reflection of the screen surface, or spots in my eyes.

color was at 50, again I wasn't sure if there were just bright spots in my eyes but I needed it that high in plain areas.

Does it sound right or did I mess up?

May I see it?  http://www.damiensymonds.net/2013/09/grabbing-700x700px-100-crop.html

3 minutes ago, meris said:

In this case, should I add the noise above to the cleaned up image?

No.

[meris]

This is a crop from all NR turned off.

Once color is cleared up, as you move luminance down there are splotches where noise appears 1st. To get those last splotches clean I'm way up.

I'm wondering if it's even just from an uneven background, it's a wall so not perfectly smooth.

[Damien Symonds]

May I see it with the 88/50 that you mentioned?

[meris]

OK here's the before again, I'm trying to get the same area

This is the after.

There still seems to be some purply splotches doesn't it?

Is that color ?

[Damien Symonds]

Ah yeah, that's the blue channel.  It always suffers the most.  Don't worry, this is great.  It'll print perfectly.

[meris]

Would you hate me if I told you I use Proselect? So that is saved as a tif, I think it's fine. But when Proselect creates a jpg from it the splotches seem to get enhanced and is visible.

So here is another that has light falloff. Taking the original tif and save as jpg, it looks like this.

 

 

[meris]

But what Proselect resizes and produces, becomes like this

 

 

You can see the banding starting to appear as well as splotches.

Is it just crappy resizing, or something I can do with more NR to get rid of that last bit?

Edited December 2, 2016 by meris

[Damien Symonds]

I'm so sorry, I don't even know what Proselect is.

[meris]

It takes the tif and resizes it (smaller) for print, saves as jpg. Basically scripts PS CC to do it.

I suspect downsizing or sharpening introduced the visible bands.

Do you have a downsizing tutorial? I only saw www.damiensymonds.net/art_resample.html

[meris]

I added some masked noise and it seemed to fix it.

 

[Damien Symonds]

Oh.my.God.