I was just looking at a thread in Gen Discussion about halos. I have occassionaly run into a problem that, for lack of a better term, I call a 'reverse halo'
Here's the scenario: I have an image with a sky and a darker area beneath it, and I want to select the darker area so that I can adjust its tone curve.
If I select any of the sky and then adjust the tone curve, I will wind up a light-toned halo. If I miss selecting any part of the dark area and then adjust the curve for a brighter appearance, I will have a lighter adjusted area, a dark band, and then the sky. The dark band is what I am calling a 'reverse halo'.
What is the best way to select the dark area so as to prevent the dark band ('reverse halo')?
Many thanks,
--P
Posted by Mark Stahlke on September 6, 2010 at 2:02 PM
I think this is an area where Tony Kuyper's luminosity masks really shine. In your scenario you might create a dark-darks mask and then do your tonal adjustments through it. If the adjustments effect other parts of the image you can paint out the adjustments on the mask.
Posted by Carol Hyman on September 6, 2010 at 4:46 PM
Mark, you're absolutely right. Preston's "halos" most likely would benefit from the Luminosity masks.
However, I have a question for you. What do you mean when you say, "If the adjustments effect other parts of the image you can paint out the adjustments on the mask." ?
Do you mean de-select the areas on the image selected by the mask? It's been my experience that if I use a square or a round marquee to deselect, I'm left with yet another problem and that's a square or elliptical area that matches nothing. If I use the magic wand tool, carefully selecting small areas, I don't have quite the problem. So the real question here is how do you "paint" out the mask adjustments.
Thanks,
Carol - use the paint brush, or eraser. Set the flow to 5-15%, set the hardness to zero, and the size to whatever is appropriate for the task.
Posted by Richard Ditch on September 6, 2010 at 5:09 PM
"paint out the adjustments on the mask" means exactly what it says:
1. select the mask for a layer by clicking on the tiny icon of the mask in the layers palette. You should see some black lines around the mask to show it is selected.
2. Set default Black/White foreground and background colors.
3. select the brush tool and pick a soft edge.
4. set the opacity of the brush to 10-20%
5. select white or black as needed for the brush and paint on the image where you want to increase or decrease the effect of that layer.
6. switch between black/white to fix mistakes
Posted by Carol Hyman on September 6, 2010 at 5:39 PM
Thanks Floris and Richard, You've solved a problem for me.
Carol
Posted by John Williams on September 12, 2010 at 11:22 AM
Boy, that opens a complicated can of worms Preston. Unfortunately, it depends a lot on what you are working with in your image. What works well for one may not for another. Tony's mask are a great place to start and a great time saver; I highly recommend experimenting with them. (With that said, I rarely use luminosity masks and find I like the results better when my adjustments spill across different luminosities.)
In general, the two approaches to directly work with the masks you describe are to create a very "tight" mask (that exactly follows and feathers the edge so that your selection is placed exactly where your adjustment will seamlessly blend), or to broaden the edge of the mask so wide that the transition is not noticeable to the eye.
I used to mostly use the former, but found it so tedious and time consuming that I rarely use a tight mask these days. Instead, I almost always use a broad-edged mask and try to use adjustments that don't push the limits of the mask.
One example is to just select the sky, create the mask, and then Gaussian Blur the mask with a radius of 200 pixels.
A slightly more complicated method would be to select the sky, and then expand the selection (the amount will vary, but try 20 pixels to start). Create a mask from this selection, and then again blur the mask as above. Fade the mask to restrict the effect to the darker side of the edge (Edit:Fade Gaussian Blur) using Lighten Mode. (Note that you have to fade immediately after the blur, and that you use lighten if you selected the sky and darken if you selected the earth.) Next, blur the mask a second time with a smaller radius (try 10 to 30 pixels if you expanded the original selection by 20 pixels). This has the effect of creating a broad transition without a hard, noticeable dark line.
Keep your adjustments gentle, and if you need more effect use another layer with a slightly varied mask to keep the transition from "stacking up" into a noticeable halo.
If you really want to go hard core, read "Photoshop Masking & Compositing" by Katrin Eismann.
Posted by Lori Kincaid on September 12, 2010 at 8:06 PM
Preston,
Try making a loose selection of the dark area, always staying within its boundaries. Make your adjustment without regard to the dark area outside the selection and then apply a gaussian blur to the layer mask until the reverse halo is negated. For a large format scan the blur radius will probably need to be 80 pixels or more depending on how large the area and how loose your selection.
That's how Charles Cramer does it and he's a master.
Lori, the procedure you outlined appears to be the easiest, and will help keep the file size in check.
I should have noted in my inititial post that I am working on master files from scanned 4x5 film. Some of my files are 900MB, or larger; so, keeping file size manageable is a big deal for me.
Discussion
8 repliesHere's the scenario: I have an image with a sky and a darker area beneath it, and I want to select the darker area so that I can adjust its tone curve.
If I select any of the sky and then adjust the tone curve, I will wind up a light-toned halo. If I miss selecting any part of the dark area and then adjust the curve for a brighter appearance, I will have a lighter adjusted area, a dark band, and then the sky. The dark band is what I am calling a 'reverse halo'.
What is the best way to select the dark area so as to prevent the dark band ('reverse halo')?
Many thanks,
--P
However, I have a question for you. What do you mean when you say, "If the adjustments effect other parts of the image you can paint out the adjustments on the mask." ?
Do you mean de-select the areas on the image selected by the mask? It's been my experience that if I use a square or a round marquee to deselect, I'm left with yet another problem and that's a square or elliptical area that matches nothing. If I use the magic wand tool, carefully selecting small areas, I don't have quite the problem. So the real question here is how do you "paint" out the mask adjustments.
Thanks,
Carol
1. select the mask for a layer by clicking on the tiny icon of the mask in the layers palette. You should see some black lines around the mask to show it is selected.
2. Set default Black/White foreground and background colors.
3. select the brush tool and pick a soft edge.
4. set the opacity of the brush to 10-20%
5. select white or black as needed for the brush and paint on the image where you want to increase or decrease the effect of that layer.
6. switch between black/white to fix mistakes
Carol
In general, the two approaches to directly work with the masks you describe are to create a very "tight" mask (that exactly follows and feathers the edge so that your selection is placed exactly where your adjustment will seamlessly blend), or to broaden the edge of the mask so wide that the transition is not noticeable to the eye.
I used to mostly use the former, but found it so tedious and time consuming that I rarely use a tight mask these days. Instead, I almost always use a broad-edged mask and try to use adjustments that don't push the limits of the mask.
One example is to just select the sky, create the mask, and then Gaussian Blur the mask with a radius of 200 pixels.
A slightly more complicated method would be to select the sky, and then expand the selection (the amount will vary, but try 20 pixels to start). Create a mask from this selection, and then again blur the mask as above. Fade the mask to restrict the effect to the darker side of the edge (Edit:Fade Gaussian Blur) using Lighten Mode. (Note that you have to fade immediately after the blur, and that you use lighten if you selected the sky and darken if you selected the earth.) Next, blur the mask a second time with a smaller radius (try 10 to 30 pixels if you expanded the original selection by 20 pixels). This has the effect of creating a broad transition without a hard, noticeable dark line.
Keep your adjustments gentle, and if you need more effect use another layer with a slightly varied mask to keep the transition from "stacking up" into a noticeable halo.
If you really want to go hard core, read "Photoshop Masking & Compositing" by Katrin Eismann.
Try making a loose selection of the dark area, always staying within its boundaries. Make your adjustment without regard to the dark area outside the selection and then apply a gaussian blur to the layer mask until the reverse halo is negated. For a large format scan the blur radius will probably need to be 80 pixels or more depending on how large the area and how loose your selection.
That's how Charles Cramer does it and he's a master.
Lori
Lori, the procedure you outlined appears to be the easiest, and will help keep the file size in check.
I should have noted in my inititial post that I am working on master files from scanned 4x5 film. Some of my files are 900MB, or larger; so, keeping file size manageable is a big deal for me.
Thanks again, all!
--P