applying a mask up to the horizon line?

[vinny]

I'm attempting to change the density (using curves) of this underexposed piece of film. (8bit,500+mb file, in cs4) I'd like to make adjustments to the top and bottom portions of the image independently. If I use the box tool with a feather of 15-25 pixels, I get some evidence of the correction (lighter sky) when adjusting the bottom half. Also, the horizon isn't perfectly flat due to lens distortion (i guess) and some tiny distant islands on the right so there's that to deal with. What's the easiest way to go about it? All that said, I'm pretty much a 3rd grade* level photoshop user so please keep any suggestions as simple as possible.






*third graders are probably more knowledgeable than myself, actually.

[retnull]

Learning to make arbitrary selections in PS is a very useful skill to have. The magic wand tool could be used here....here's the first tutorial that popped up on Google: http://www.youtube.com/watch?v=K9zJts240Vk

Once your selection is made, you can do levels or curves on just that region. Then you can invert your selection to work on everything else.

[Lenny Eiger]

There are a number of ways to make masks. Selecting with a tool like the lasso, for example, is the least effective. The issue is the smoothness of the transition between the masked area and the area that is being curved, or adjusted in some other way. Feathering can help, but it isn't great....

The essential tool for this is the Wacom tablet. This allows you to paint the selection, and is controllable in ways you can't imagine until you have one.

There are three main ways to do this:

1) Start with a lasso, or box tool selection (I think its actually called a marquis). Paint over every edge to smooth it out. If you are dealing with buildings they are straight, but horizons rarely are.

2) Select by Color Range. Choose the background layer, then choose select by color range and click on the color (or tone, if in b&w) you want to highlight. Move the slider until you get closest to what you want... then get the rest of the way with the pen tool.

3) Channel masking. You can copy any channel you want and turn it in to a mask. This is very useful when you have an area that is best outlined by the computer, where a brush would take 10 hours to select and you want it to be accurate. (Color Range does this as well.) You can look individually in the R, G and B channels, or even flip into other color modes and select the Y channel if you want, and see which one best outlines what you are looking for. Then finish off with the brush.

The luminosity masks that get talked about often are simply done by selecting the whole thing RGB e.g., and making it into a mask. You can use the curves to adjust it to cover only the shadows or highlights, etc. just by making it darker, lighter, etc. It's too easy.


Masks are made by selecting some portion of the image, then adding a new adjustment layer. The selection has three modes, the marching ants, the quick mask and what I call the black and white mode. In both the quick mask and the black and white mode, you can paint right on to the mask you have made. Painting on it selects more it it, or deletes the selection. The Quick mask is usually set to be translucent so that you can paint over it while you are looking at the image.

(One difference that throws some folks is that the black and white applies your change directly, while in the Quick mask, you have choose the adjustment layer and save the selection over itself to replace it. )


With a table, painting the detailed part becomes artful. One often starts with a small brush, then one backs off the edge and goes to a larger brush and sprays a subtle amount to smooth it...

The real fun comes when you add and subtract masks from each other. It's always best to control parts of an image with one layer, rather than having one layer that makes it lighter, then another one darker, etc. I often start out with a main curve with no masking, and then I drop a portion of it out if I want to control it separately. In your case, I would select the sky, then invert it and make a new layer so that the top and bottom were controlled on different layers. That way, as I make micro adjustments, I can do it only in one place, rather than having to correct multiple layers to change one thing. With a mountain in the background that isn't sharply focussed, the partial selections can be a quite difficult...

I didn't have much sleep last night, daughter went on a trip to airport very early, so I hope this makes some sense....

Lenny

[Henry Ambrose]

Use the lasso tool at 100 or 200% view to refine your selection as shown, save the selection, then copy it to another layer. Go back to the base layer and use your saved selection to select the same area again, then inverse that to select the balance of the image and save that to a new layer. You now have 3 layers; base, ground, sky. Do a save as so you can come back here if you mess up. Work on them independently as you wish then do a manual feathering to the areas of intersection with the eraser tool turned down low. Experiment with opacity of the layers to get a blend that looks just right. That's the brute force method.

[adam satushek]

I think Lenny is right on about the Wacom tablet. I didn't really understand thier benefits until I started masking.

I guess I use masking in a pretty reudimentary way compared to what Lenny describes, but it is still very powerful.

Basically, I usually start by creating a new Curves adjustment layer, and use this for global contrast and color adjustment. Often times there is an area that is too light, like a sky. I will then select the mask layer that is automatically created next to the original adjustment layer and use the brush tool with black foreground selected to paint out the area you don't want affected by that curve layer. The X hotkey is nice as it allows you change between painting white/black very easily. The key to this is big soft brushes and the presure sensitivity of a Wacom. It take some practice to know how large or soft of a brush will give you the feathering you need, but I find this much easier than feathering lasso selections. If I need to darken/lighten the area more I just make another Curve adjustment layer mask off the portion I dont want to affect and make the adjustment.

It takes some getting used to but I am able to use the brush tool in combination with curves to do pretty much everything I need to do in Photoshop.

[Peter De Smidt]

I would use the pen tool. It takes a bit to learn, but it is very useful. You can then refine the selection, if feathering (or similar) is needed. I usually only feather a few pixels at most. 15-25 is a huge amount.

I don't like using Wacom tablets. (I've had a 6x9" Intuous3 for years.)

[Lenny Eiger]

I would use the pen tool. It takes a bit to learn, but it is very useful. You can then refine the selection, if feathering (or similar) is needed. I usually only feather a few pixels at most. 15-25 is a huge amount.
I don't like using Wacom tablets. (I've had a 6x9" Intuous3 for years.)

Peter,
Come on over, I'll give you the advanced lesson in how to use that thing. I think you'd be amazed at how it improves the workflow..

I have a 6x11 one. I was initially quite skeptical about them, I even asked someone at a MacWorld Expo, at the Wacom booth how to use one (for something other than retouching) and they couldn't tell me. Ultimately, I found someone who was a real pro, worked for George Lucas at Industrial Light and Magic (where they take this stuff very seriously), and he showed me the ropes. It's a good thing because I had a hundred hours of removing backgrounds to do, I had already done it with the hard-edged tools and feathering the images all looked like paper cutouts.

I would say the pen tool is ok, but its the same as selecting with the lasso, the marquis, the magic wand or any other "hard edge" tool. When you talk to the pros, they can all use those tools where appropriate, but no one I have ever known would suggest them for completing a mask. There are all sorts of tricks, every damn book has something about "just do this" for one thing or another. These things are no substitute for the long way around.

Lenny

[Peter De Smidt]

Never mind. My future policy will be to not post in a thread that Lenny posts in. He always wants everything to be a contest, and I'm tired of it.

[vinny]

ok, before this goes any further (and I get more confused), I don't own a tablet and won't be purchasing one in the near future. I used one briefly and didn't like it that much. I'll try the suggestions that apply to me. thanks

[Lenny Eiger]

Except that with a pen tool you can make very intricate curves and the points on the path can be adjusted whenever you like. It's terrific for hard (or semi-hard) edges. Isn't that what we have here?

Honestly, I don't actually think so in this case. We aren't actually looking at the file, its true, so we can't really know. However, my thought is that there are certain types of edges where a pen tool is useful. Generally, they would be harder edges, like a building.... When I have worked on images from the natural world (its most of what I do), and looked closely, these kinds of lines tend to have a million little ups and downs in them. Enough feathering would simply straddle the line, and trying to paint the whole thing isn't useful either - it might take forever, up at 200-300%. I think a mask made with select by color range, or a channel mask could get most of it - or at least half of it. I would get one half with one selection, then get the other half, then combine the masks to get 80-90% of what I want. Then I would take out the brush and do my best on the rest.

Lenny