Best way to lighten/darken parts of photos in GIMP 2.10


(Stampede) #1

I have a picture with the subject lit by a nearby streetlight. There is an interesting background behind her. I’d like to boost the brightness of the background by about 1 stop and leave the girl in the photo alone. So I want to selectively brighten part of the background.

What is the best way to do this? In my film days, we dodged and burned in the darkroom. I have watched a lot of youtube tutorials for GIMP and it seems people seem to make a new layer, set to “overlay” and then paint black or white on top of it, then adjust transparency of layer. So maybe that is how to do it in the digital world.

OR, though I have not seen it done this way, I could make a new normal layer, adjust the curves on that layer and paint a layer mask on the new layer so the curves adjustment only affects the parts of the image that I want.

What’s the best approach to this? I’m running GIMP 2.10.0 in Ubuntu.


(Mica) #2

We have a luminosity mask script in our github repo: https://github.com/pixlsus/GIMP-Scripts/blob/master/sg-luminosity-masks.scm


#3

@Stampede

Also: you have dodge/burn in The Gimp as well :slight_smile:

Have fun!
Claes in Lund, Sweden


(Pat David) #4

Odd if you haven’t seen this. That would have been the first way I figured someone would have approached this. I would try this if you have a good separation between the subject and the background - otherwise it becomes very apparent that work was done on the image like this.

You can try a luminosity script, and target only the tones in the background. Then just add a copy of your base layer, adjust the background to taste, and apply one of the luminosity layers (D?) to isolate the subject.

I’m not near my workstation at the moment, otherwise I’d see about making a quick video to illustrate my thought… Did you have an image you could share for us to see the problem better?


(Stampede) #5

Thanks for the help. I read the two tutorials on luminosity masks and installed the script that @paperdigits suggested.

@claes Yes, I’m aware of the dodge/burn tool in the Gimp. But in the videos I have watched (mostly found through Youtube searches), no one seems to use it. Though, I did see one tutorial that used layers and the dodging tool to whiten people’s teeth in portraits. As I mentioned in my OP, it seems painting white/black on a layer in overlay mode seems to be more popular, at least in the videos I’ve seen.

@patdavid I am going to try and upload a picture to this post to show you what I mean. I would like the triangle background a little lighter, especially the borders to the triangle. I’m not sure the best way to do things like this, though I did get acceptable results using the luminosity masks script and manually painting parts of the mask that I did not want to change, like over the girl’s black T-shirt.

I’ll sometimes shoot studio stuff with flashes and my lighting ratio is off (though I try to avoid it in camera, obviously)

, so whatever I learn from this picture, maybe I could also use to make shadows lighter or darker in such cases?


(Mica) #6

I do this a lot as well. Rarely can I use the luminosity mask straight from the script without modification. The script saves a lot of time though.


(Boris Hajdukovic) #7

Besides luminocity masks there are many other ways to brighten the shadows.
A very interesting technique is described in this video:

Duplicate the layer, desaturate and invert this new layer:
desaturate = menu “colors” > desaturate > desaturate
invert = menu “colors” > invert

Blend it with “overlay” blend mode (choose it from menu “mode” in layer tab) :

Photo looks very flat now. To avoid that, apply grayscale copy of that layer as mask:
(right-click on layer chose “add layer mask” and in new dialog choose “grayscale copy of layer”)

Now you can see that the shadows are already brightened:

Maybe that is already enough :slight_smile:

If not, then you can influence the brightness of the image even more with the help of color balance tool:

Duplicate original layer two times and move them both over inverted layer.

First layer over inverted layer should have “HSV saturation” blend mode, second (above that one) “HSV Hue”:

Hue_Sat

Now select again original layer and open “color balance” tool:
(menu “colors” > color balance)

Bildschirmfoto_2018-05-14_20-03-35

Chose “shadows” and move color sliders to your taste. I moved slider towards magenta and yellow a bit and got good results:

Before and after:


#8

@Stampede

@s7habo’s suggestion is basically using a softer DD luminosity mask. For a more nuanced approach, refer to @McCap’s tutorial on masking with curves. As you become proficient, you should be able to do a lot of cool stuff like this (another tutorial by @McCap).


(Isaac Ullah) #9

How about SIOX foreground select to isolate your subject, and then invert the mask and raise the levels only on the background?


#10

I find myself using the free select tool more than the foreground one. I.e., I cannot use the latter without using the former to clean up the selection. A good way to trace your subject and see where your edges are weak is using gradient_norm.


#11

I just used the zone system in lightzone or darktable. Both can lighten the dark background by just moving the marker for the zone, leaving the subject zone unchanged. This is done in lightzone and it is real easy.