(07-10-2025, 04:59 PM)AWysy Wrote: Hi,
Just started to use GIMP. I am making my first experiences.
I have one question concerning Blur/Sharpen tool. After blurring and switching to sharpening the blurred part does not "return" to the original by applying the sharpen too. However after the sharpening, blurring functions. Is this normal, or some of the settings need to be changed.?
Thank you
To complement what others have said:
Gimp is a bitmap/raster editor. Most things that change the appearance of the image are "destructive", in the sense that even if you know what you did, you cannot recover the exact original state by applying a further edit. For instance rotating the image 10°, and then rotating it back 10° will slightly blur it. These are inescapable rules, but...
- There is an Undo (Ctrl-Z)
- There are several techniques to avoid editing the original image:
- Add layers (you can then remove/amend these new layers later and recover the exact original image)
- Use layer masks (the masks tell Gimp to consider that some pixels are erased, but if you remove/repaint the mask they are unerased)
- Since Gimp3, use the "Non destructive editing" (aka NDE): some filters can be applied "on the fly" to layers: Gimp keeps the original layer and the definition/parameters of filters, so filters can be tweaked/removed later.
So, an important skill is to plan in advance what you are going to do, so that you set up your layers/masks/filters to delay the reall editing as much as possible.
Let's take an example: you want to blur part of the image, and then figure out that you blurred too much
- Beginner version: you apply a Gaussian blur, and then get stuck because no sharpening is going to recover this. If you see this soon enough, you can Undo, but if you find out later, you will have to delete a few more processing steps.
- Skilled Gimp2: you copy the parts to a new layer and blur the new layer. At that point you can to some extent adjust the amount of blur on the composite image by reducing the opacity of the blurred layer, and in the bad cases you just erase that layer and redo it, while keeping other processing done later in other parts of the image.
- Skilled Gimp3: you apply the Gaussian blue as a non-destructive filter (ie, not merged). You can come back later, summon the Gaussian blur settings and tweak the amount of blur and see its effect on the whole image, including some processing steps you did after adding the blur.
For instance, in the attached image, the whole image is sharpened by subtracting a slightly blurred version form the original. If you open the image (in Gimp3...):, you can tweak the sharpening in two ways:
- Adjust the opacity of the Blurred layer (more opaque: more sharpening): this would be the typical Gimp2 way
- Click the fx icon, select the Gaussian blur, click the pencil icon to edit the settings, and change the blur amount: this is the typical Gimp3 way (which can still be combined with an opacity tweak).
