Need help: filter pixelation and compression artefacts on upscale

[rich2005]

Quote:Yes I would prefer a better scan but the artist seems to be unable or incapable of providing a better one.

I wonder....? Some formats, jpeg and in particular tiff can include a thumbnail of the main image in the file metadata. Sometimes it is the thumbnail that gets loaded. Some investigation needed but there are graphic tools that will strip the meta data leaving the main image.

[Chocobo]

(04-28-2022, 06:59 AM)denzjos Wrote: Maybe this free software to enlarge images can help you : https://www.reshade.net

Yes that one work fine, very simple to use. There is a resolution limit, making huge upscaling not possible, but other than that it is a nice too for this.

@rich2005
The plugin is more complez but there is no resolution cap. I used it on a low powered and old pc and brought it to its limits rather quick. Im going to use it on a high powered pc, I guess if I dont push it too much it will be fine. Its a suitable tool to fix the issues with the scan. Thanks

No no its not the thumbnail. Its not that low res. The scan was 600dpi. Maybe higher dpi and tiff format would do the trick. This scan is just bot high fidelity enough (600dpi jpg) for the extreme close ups I need to do.

What would you guys want to see if you ask for a really high res scan. 1200dpi tiff? Or even higher? I am completly clueless about this subject.

[rich2005]

Quote:This scan is just bot high fidelity enough (600dpi jpg) for the extreme close ups I need to do.

For a scan, 300 ppi (photo quality) is sufficient. 600 ppi is really a maximum but it depends on the scanner, 1200 ppi usually an interpolation and not always better quality, just larger.

From your posts you are doing some extreme manipulation. Try thinking of other ways. Get someone with a good camera, good lighting, good macro lens and take a photograph of the area of the painting you are interested in.

This with a cr*p camera (mobile phone), poor lighting (sun is setting here), and a 10 euro clip-on macro lens.

It is the center of a postage stamp. An area about 1 cm x 1 cm

   

[Chocobo]

Thats good to know. So 1200dpi may not be better at all. But tiff should be an improvement.

[rich2005]

(04-30-2022, 12:11 AM)Chocobo Wrote: Thats good to know. So 1200dpi may not be better at all. But tiff should be an improvement.

It will depend on the scanner quality.

Things to ask for: 
If the scanner outputs a 16 bit image get a 16 bit image. Jpeg does not support 16 bit but tiff does.
By all means try 1200 ppi
A tiff file can be uncompressed or lossless compressed. It will be a (much) larger file size.
No jpeg compression so none of the jpeg compression artefacts that concern you.

[Chocobo]

Thanks for the response.

Okay, I will ask the artist next time to:

-try 1200dpi but also do a 600dpi version if the 1200dpi is interpolated
-go for tiff
-set to 16 bit if possible

If it is a usual scanner anything higher than 1200dpi is unlikely to be supported?