JPEG Quality Issue

[d0m1n1k]

Hi gimp users,

I got JPEG images from a multifunction copier. I really like the quality per size of these images!
I would also like to use this jpeg quality with gimp exports. But this doesn't work as expected. First I opened an image generated by the copier. Then see attached 3 screenshots from export dialog:

1 - these are the standard values. It produces a very big size jpeg. This is not what I want.

2 - these settings are automatically choosed, if I just check the "Use quality setting from original image" checkbox.
The exported image with this settings is very good. The size is even a bit smaller than original. This is what I want! I like to use this quality settings for default at all images!

3 - But if I uncheck the "Use quality setting from original image" and keep all other settings changed before, I got an image with horrible quality.

Why can I not use this quality level by choosing the settings gimp choosed? It's absolutely insane: The only workaround I found to use this quality level is:
1. Open my own image (not generated by multifunction copier)
2. Copy the whole image to clipboard (Ctrl-C)
3. Open any image generated by the copier
4. Chance canvas size of this image to the image size from my own image
5. Paste my own image from clipboard (Ctrl-V)
6. Export with "Use quality setting from original image"

[Ofnuts]

If you don't use the image settings, you get Gimp's default values. So what you probably want to do is to saved these values as default (button at bottom of dialog).

Note that settings that are good for an image from a multifunction copier may not be good for another image type (from a camera; etc...). So you should better understand what the settings do and pick settings explicitly.

[d0m1n1k]

(Yesterday, 04:21 PM)Ofnuts Wrote: If you don't use the image settings, you get Gimp's default values. So what you probably want to do is to saved these values as default (button at bottom of dialog).

No, "Dialog1" are the default values. If I check and check "Use quality setting from original image" the values are changed automatically. (e.g. quality to 5, and rhe subsampling setting - I didn't changed it by hand).

I also explicitly tried different quality levels by hand. But none has even come close to the quality and size of Checkbox "Use quality setting from original image".

[Ofnuts]

Q5 is usually terrible, so there is something amiss or your image has some very specific content (monochrome?) that makes Q5 palatable, but your changes require some better quality.

Q90 (left)  vs Q5 (right)

       

Can you share your original image?