Adding preview windows for very low and ultra low frequency and increase their adjustable amount over +150?

[lansing]

I have found that the very low and ultra low frequency denoising very effective on cleaning out bleed through problem from scan, where things from the back of the page bleed to the front.

I would like to request the addition of preview windows for these two domains. Also the adjustable amount of +150 is not enough. On my scanned comic, I need over +150 on very low/ultra low frequency to remove the bleed through.

[NITeam]

Thank you for the suggestion regarding previews. We will consider possible options.

Regarding the adjustable noise levelif you need more it than +150%, then that may indicate that the noise profile is not accurate. It may be necessary to re-build the noise profile using a good sample of very low / ultra low frequency noise itself. This will more accurately measure that noise and you will not need to adjust it in the filter settings so much.

Vlad

[lansing]

Hi I tried building the auto profile using the the bleed through area, but it still doesn't covers it in the result.

Here's a sample image. Look at the soft curve line on the right.

I changed the image to grayscale in photoshop and feed it to Neat Image. In setting I maxed luminance noise reduction amount, mid/low/very low/ultra low frequency noise level, and turned off high frequency noise level. In the frequency windows I didn't see it but it was still there in the normal preview window, so it means it still lies somewhere in the very low and ultra low frequency domains.

[NITeam]

Please try these profile/preset to see if you get the same results with these as with your profile and filter settings.

Thank you,
Vlad

[lansing]

Hi your test profiles worked when running under RGB mode, with no soft bleed through left over. So is it the grayscale mode that I was using the cause of the problem?

If I'm to have my final output as grayscale, I should first run Neat Image->convert to grayscale instead of convert to grayscale->Neat Image?

[NITeam]

Probably that is not related to the RGB vs grayscale. I guess. Perhaps this is more about the profile and filter settings that I used. Notice that I increased the noise level in the filter settings. Also, I built the profile using a large area that included those bleeding lines. I think these two things together allowed to reduce those bleeding lines.

Vlad

[lansing]

Out of curiosity, I did a side by side comparison on the effect of denoising in rgb vs grayscale. I make the noise profiles both from sampling the curve line on the right of the image and then use the same noise filter setting from your zip. Then turned down the brightness of the preview window to the minimum to help easier spotting differences.



From the comparison, looks like the RGB mode denoise the bleed through a little better.

[NITeam]

Perhaps a bit better in RGB but still quite noticeable.

It is not really noise after all, so it is not reduced just as well as the regular random noise.
As far as I can tell, tweaking the filter further will likely not give better results.

Vlad

[NeatOliver]

To me, Neat Image always struggles to fully remove ghost-like artifacts, heat-induced distortions, or wiggling effects from an image, especially when dealing with very low-frequency noise. This is unfortunate since these types of disturbances are technically a part of "noise" so to speak, and not something "natural", real, solid or crafted by man but still in the image.

So, despite its advanced noise reduction capabilities, with Neat Image, certain visual anomalies, such as faint residues or heat-related interference, things of that nature, may remain due to the complexity of the noise pattern and the challenge of separating them from real image details. So, while Neat Image offers fine-tuning options to enhance noise suppression, unfortunately, some subtle remnants might persist, particularly when they look like a ghostly residue rather than random pixel noise.

Perhaps this could be introduced as a new additional filter option for the next version of Neat Image, maybe called "Ghosting Effect"? Similar to 'Artifact Removal', 'Detail Recovery', 'Edge Smoothing', and 'Sharpening' filters in Neat Image? That said, I find it strange that we can only preview the 'High', 'Mid' and 'Low' frequencies, while the 'Very Low' and 'Ultra Low' frequencies remain definitely not available as previews in Neat Image, although they can still be adjusted.

I tried using the sample image provided by Lansing, with his image >> HERE << and with my own settings, which you can download >> HERE << so you put these files in the 'Device Noise Profile' and 'Filter Settings' folders in Neat Image and see it by yourself what I did. I tried to be very precise with the 'Device Noise Profile', and with the 'Filter Settings". But I couldn't find a way to correctly detect the 'Very Low' and 'Ultra Low' noise, even though we can clearly see it on this this white paper sheet with the naked eye! It's really bizarre, if you ask me. It's clear that these shapes resemble the heads of two manga-style children, complete with hair, eyes, and ears.

So, to me again... the 'Very Low' and 'Ultra Low' noise profiles in Neat Image are more of an added feature rather than a truly precise and effective solution, at least for images like this. Clearly, this limitation has persisted since Neat Image was first developed. For now, it feels like a somewhat underwhelming option to me due to this technical fact.

Hopefully, Vlad and his team will refine and improve this feature in the next version of Neat Image!

[NITeam]

Thank you for your suggestion. The visualization of the individual frequency components is indeed limited to High, Mid and Low in the current version of Neat Image. Hopefully this can be improved in the future to facilitate more accurate tuning of the filter settings in the Very Low and Ultra Low components as well.

Thank you,
Vlad

[NeatOliver]

GREAT! You're welcome, Vlad.
Thank you for your reply.

[NeatOliver]

By the way, the only way to get rid of this ghosting effect (90% effective) is to use the Blur, Surface Blur filter in Photoshop (Radius 60 / Threshold 14).
So "maybe" the next version of Neat Image will also be able to use this type of approach for the 'Very Low' and 'Ultra low' frequencies?

[NITeam]

Blur is a very strong tool indeed.