curves...

[oTTer]

Ok, I've tried using curves, I've looked it up online, and I am not understanding what difference the adjustment using curves is, compared to using the bright/contrast or color balance tools. I could see if it was affecting part of the picture, but I don't see that happening. Like the rose below, I could see the stem being brighter in the second one, but when you darken the whole shot, the only way to pull that back is the history brush (I think) and it might look odd having a bright stem with a dark flower (and really, who cars about the stem) but let's say I want the stem to stay lighter. Will curves darken part of the picture, or ? From what I gathered, it adjusts the overall picture. I know people have lightened or darkened part (top or bottom half, say) of a photo... I have a PS7 book, I'll see if I can find it, and see if it gives more detail than what I found online.

[bob_r]

You can put stop points on the curve so different areas can be curved differently. I played around with Ed's flower in curves to give you some idea.
The first shot is Ed's original shot. Notice the histogram. I did an "auto curves" on it and that extended the right side of the histogram to the end (see image). I saved that and then reopened curves again and did a little manual adjusting and saved that.

This is the original file showing the histogram.

curves_original.jpg (75.51 KiB) Viewed 1659 times

This is the auto curves adjustment.

Curves_auto.jpg (79.62 KiB) Viewed 1657 times

This is after the all the curves adjustments. I didn't use any editing tools other than curves.

Flower_after_curves.jpg (87.93 KiB) Viewed 1657 times

[bob_r]

Here is a pic of the curves chart showing different stop points set (this was just for demonstration - you wouldn't have this many).

Curves adjustment chart showing how stop points can be set.

curves_stop_points.jpg (40.61 KiB) Viewed 1653 times

[oTTer]

From your second demo, it looks like you adjusted your three colors, which is something I can do in the image: adjustments thing. So why use curves? I guess I see on the curves chart, there is a dark to light ratio along the side, but I don't understand how that corresponds to the image you're working with. I've moved the thing just a bit in some snow shots, and areas almost completely disappear so I must be eliminating something, but I can't tell what it is I am eliminating. I think the curves app is more complicated than what I've been using it for, and I just need to learn how to use it. But isn't there a gradiant tool that you can use, that you can adjust an image just at the top or bottom?

[bob_r]

From your second demo, it looks like you adjusted your three colors, which is something I can do in the image: adjustments thing. So why use curves? I guess I see on the curves chart, there is a dark to light ratio along the side, but I don't understand how that corresponds to the image you're working with. I've moved the thing just a bit in some snow shots, and areas almost completely disappear so I must be eliminating something, but I can't tell what it is I am eliminating. I think the curves app is more complicated than what I've been using it for, and I just need to learn how to use it. But isn't there a gradiant tool that you can use, that you can adjust an image just at the top or bottom?

The gradient tool is used to adjust colors whereas curves adjusts the brightness. I'm not sure what you mean by the "dark to light ratio along the side", but the histogram is displayed and as you make adjustmets to the curves, they are reflected in the histogram.

[oTTer]

"Curves adjust brightness."
Then why not just adjust the brightness with the brightness/contrast tool?
The curves thingy has the RGB and also the individual selection for each color... are you talking about adjusting the brightness of each color? If I move the line at the bottom left to the left, and I move the line at the top right to the left, what is being adjusted? I guess I don't understand why moving the line at the bottom one way or the other, how that correlates to the picture. ? Am I adjusting the brightness in the bottom left of the picture? Of course not... so what is the difference in what I am adjusting in the bottom left as opposed to the top right? I know sometimes it washes a color completely out, or blackens it... but I have no idea what I am doing, and what it is that I am doing is controlling. Kind of a hit and miss deal.

[bob_r]

Pam,

Here is a link to a tutorial that explains curves much better than I can.

http://www.cambridgeincolour.com/tutori ... curves.htm

Hope this helps.

Bob

[Edd]

Otter,

I think you may find that Curves is a little more selective than a brightness/contrast control.

Brightness and Contrast tend to change the whole image where as using curves you can just adjust certain things like shadows and highlights.

Hang on, I used curves today on a photo my wife took of one of our horses I'll just dig them out.

Back in a few minutes.

Ed

[Edd]

Well it appears that Bob may of beaten me off the mark. But here goes.

This is the original image but cropped to size.



This is the edited version. I did a slight adjustment on levels to make the rug look a little brighter, then after Bobs note yetserday I used curves to lighten the shadow on his face. My version of curves is no where near as complex as Bobs, I have just a bunch of presets (I used Lighten Shadows preset) the I did a very slight adjustment of the mid tone (I think) slider. Sharpened with USM.



Hope this helps.

Ed

[bob_r]

Very well done, Ed.

[Edd]

Cheers Bob

Ed

[oTTer]

I guess I would have to ask, What did you do to redden the blanket? Move the diagonal line up at the bottom? Down at the top? And did that automatically lighten the face, or did you have to do something else for that? I've tried different things, and have completely made a color turn a funky chalk color. I don't know why moving the line at the bottom one way does it and moving it at the top doesn't. I don't understand what along that line controls what. Is it hit and miss, or is there something somewhere I should know? For instance...

an original photo of the sun over the platte river

and then I moved the curves


So, I am not sure what improvement on the original there is to make, if the original photo sucks to begin with. I read somewhere that you don't want the fake halo look around the sun, so curves can get rid of that... I also noticed that if you move the line one way, say down, the entire picture lightens or darkens, so you have to move the curve the other way to keep it from being too much, or you can overdo that too. I can't tell if I move it up and down in an S fashion that I am not doing much of anything, and which part of the S being higher or lower did what where and how much. So, is it hit and miss? Or...?

[bob_r]

Pamela,

Curves isn't going to offer much improvement for this picture. The main advantage it holds over "brightness/contrast" is that it allows you to manipulate the different regions of an image. Your highlights may be perfect but detail may not be visible in the shadows (as in Ed's picture) and it allows you to draw them out. It also allows you to reduce the highlights to a more acceptable level (as I tried to do with Ed's flowers). There are no tools that will allow you to create details that are completely blown out (as in this picture). When you exceed the dynamic range of your sensor, those details are lost forever. Details in shadows have always seemed easier for me to recover than details in highlights so if I know I'm going to have problems covering the entire range of a scene (and don't have any GND filters available), I try to capture the highlights and hope I can pull some details out of the shadows during post processing.