A GIMP Question

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This post is directed to Ian Wilson since he so graciously provided an excellent GIMP tutorial almost a year ago in the thread I started called Photog Assistance Needed.

Ian, if you happen to read this, the reason I put it here as a post rather than a PM is the fact that the old thread and what I might learn now could be of some help to someone else as well. I welcome comments or assistance from others as well as Ian.

In [post=’750019′]this tutorial post[/post] you used the layers and blend tools to help me get rid of dark areas in a photo and I was quite successful in that adventure.

I now have another (Christmas) photo I took this Christmas where I accidently let my klutzy finger get partially in the way of the flash AGAIN! Most of my other shots are OK for I was trying to be careful of the flash. The picture in question has my daughter-in-law in the upper left corner, exceedingly dark because of my errant finger. However, sitting below her leg is a trash bag where she was gathering up wrapping paper for disposal.

When I use the layers and blending technique to take out the darkness over her image, the white trash bag becomes offensively bright. I’m using a vertical blend rather than a horizontal.

And therein lies the question. Is it possible to do this layer-blending trick so that I lighten (brighten) up ONLY the upper left quadrant of the photo? In other words, can I somehow use a combination of horizontal AND vertical blending to achieve the result I want? Here’s a somewhat reduced copy of a rather large picture. And THANKS!

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While I’m waiting, I decided to post an example, before and after, of my amateur photoshopping so far. The red box shows how I’ve “corrupted” the lower LEFT quadrant of the photo.

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While I’m waiting, I decided to post an example, before and after, of my amateur photoshopping so far.  The red box shows how I’ve “corrupted” the lower LEFT quadrant of the photo.

Hi there, Al.

One way of doing what you want is to work some more on the layer mask after you add the blend to it.

So following the method we discussed last year you’ll have duplicated the original layer, added a layer mask and applied a blend to the layer mask (in this case shading from black on the right to white on the left). And you’ll have set the layer mode to screen.

Now remember that the point of the layer mask is this – where the layer mask is black, the layer is effectively hidden, and where it is white it is visible. So the “screen” layer mode has no effect where the layer mask is black, full effect where the layer mask is white and a partial effect where the layer mask is grey. So here is what you can do. (Before going on, duplicate the layer with the layer mask again so that it is easy to go back to it if you want to, and then hide that second copy by clicking to get the eye symbol to disappear.) Make sure you then make the layer with the mask that we do want to use the active (highlighted) layer again and that the layer mask is selected (has a white border round it). Then select a fuzzy brush from the palette, set its opacity somewhat less than 100% and the colour to black. Paint over the part of the image you want to darken. The black painting won’t appear on the image itself, but it will appear on the layer mask which will have the effect of darkening that part of the picture. If the effect is too marked, use Undo, and either set the opacity of the brush lower, or paint with a shade of grey instead of black. 

Funnily enough, I was thinking of you only yesterday because I was doing something similar to a boxing day lunch photo, and remembered last year’s thread. I had used the flash, but the nearer people were better lit than the farther people. So I did the same thing we previously discussed to lighten the photo towards the top. But then the scene outside the window was too light so I painted some black on the layer mask where the windows are and some white where the faces are as I wanted to lighten them a bit more. You can see this below. The layer mask is basically a blend from black at the bottom to white at the top with some selective painting added.

I hope this helps!

Ian

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How is this?
There is an issue with graining in the area that has been lightened. I managed to reduce the graining a bit but it is still noticeable.

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How is this? There is an issue with graining in the area that has been lightened. I managed to reduce the graining a bit but it is still noticeable.

It’s certainly better than mine. But before I ask WHAT you did, the important thing is WHICH software did you use to do it with? I’m kinda familiar with Gimp and have PSP as well. I absolutely can’t figure out where to go in PSP so that’s why I reverted to Gimp.

And hey, thanks for the work Tony!

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I used Photoshop, applying a non-destructive dodge and burn technique. I do not use either PSP or GIMP, but you may be able to apply a similar technique in those applications. The technique allows you to lighten or darken just the areas that you want.

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 Another approach to your photo in this case would have been to duplicate the layers and set the mode to screen, as before, add a fully black layer mask to the top layer but then instead of adding a blend to it, just paint white on the layer mask where you want to lighten the picture where your finger had obscured the flash. You’d need to do it a little at a time, perhaps using the airbrush tool, and with the brush opacity set low, or even painting with a shade of grey rather than white. You’d need to avoid a hard edged brush as you don’t want to see a sudden obvious change in brightness on the picture. This would be something similar to Tony’s approach. (You could just use the dodge and burn tool directly on the photo, but that is not non-destructive. Using a layer mask means you can undo whatever you want.)

Ian

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 Another approach to your photo in this case would have been to duplicate the layers and set the mode to screen, as before, add a fully black layer mask to the top layer but then instead of adding a blend to it, just paint white on the layer mask where you want to lighten the picture where your finger had obscured the flash…

Thanks very much, Ian. This is good “homework” for me and I’ll start my practicing later today.

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Thanks very much, Ian.  This is good “homework” for me and I’ll start my practicing later today.

This is a quick attempt by me, trying not to overdo it so that it doesn’t become too blotchy.

And here are what the layers looked like. I added a blend to the layer mask on a bit of an angle and then painted on the layer mask with black over the rubbish bag.

Ian

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Funny thing is, now that I think about it, I was trying last night to do something similar to what you describe, except that I didn’t know you could work on the opacity of the blend as you’ve now described.

I was duplicating the background layer and on each duplicate I was blending from a different direction, trying to continue lightening my DIL without too much impact on other parts of the screen.

Onward now with YOUR instructions to see what kind of “artist” skills I’ve got, or lack as the case may be…

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Funny thing is, now that I think about it, I was trying last night to do something similar to what you describe, except that I didn’t know you could work on the opacity of the blend as you’ve now described.

There are two points at which you can think about opacity. If you use a brush to paint onto the layer mask, the brush doesn’t have to be 100% opaque, so you get a more subtle effect. You can always go back over the same area later if the effect isn’t enough. And you can adjust the opacity of the upper layer if the overall effect is too much. (And if it isn’t enough, you can duplicate the upper layer once you’ve finished. If that is then too much, the opacity of the topmost layer can be shaded down a bit. So can effectively add say one and a half layers.)

But you do have to accept a compromise between pulling the brightness up a lot and the quality. There is not much information in the dark area, so it will be blotchy there if you pull up the brightness as much as you would ideally like to.

Ian

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There are two points at which you can think about opacity. If you use a brush to paint onto the layer mask, the brush doesn’t have to be 100% opaque, so you get a more subtle effect. You can always go back over the same area later if the effect isn’t enough. And you can adjust the opacity of the upper layer if the overall effect is too much. (And if it isn’t enough, you can duplicate the upper layer once you’ve finished. If that is then too much, the opacity of the topmost layer can be shaded down a bit. So can effectively add say one and a half layers.)

Wow, boy I’m gonna have to save and print this thread to add to my other tutorial! I’ve learned so much from you, Ian, and I hope the value of having it here in The Lounge will help others as well.

I can’t thank you enough. This business of photo editing could become a full-time passion if one’s not careful…

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This business of photo editing could become a full-time passion if one’s not careful…

Indeed!

Ian

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