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DPChallenge Forums >> Hardware and Software >> Let's learn photoshop - curves
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07/10/2012 08:54:35 AM · #1
Ok -- this will probably fall flat, but I thought it was worth a try.

It seems like there's so much you can do in photoshop, yet I'm in my little rut of doing the same things over and over again without learning something new. So I thought about picking a topic and seeing if we can teach each other what we know.

So I thought I'd start with curves:

I have a tendency to use the presets -- linear contrast, medium contrast, and then play with the little dots (adding and subtracting them). Every once in awhile I remember the eye droppers on the left. And I've never touched the individual red, green, blue channels.

Do you use curves? Is there anything you can teach us? Wonderful tips and tricks? How do you approach it? Or does everyone just tweak the presets?


07/10/2012 09:02:54 AM · #2
Originally posted by vawendy:

Ok -- this will probably fall flat, but I thought it was worth a try.

It seems like there's so much you can do in photoshop, yet I'm in my little rut of doing the same things over and over again without learning something new. So I thought about picking a topic and seeing if we can teach each other what we know.

So I thought I'd start with curves:

I have a tendency to use the presets -- linear contrast, medium contrast, and then play with the little dots (adding and subtracting them). Every once in awhile I remember the eye droppers on the left. And I've never touched the individual red, green, blue channels.

Do you use curves? Is there anything you can teach us? Wonderful tips and tricks? How do you approach it? Or does everyone just tweak the presets?


I usually use curves for contrast in basic editing, when you can't use layer blending. I prefer to adjust contrast by duplicating a layer, setting to overlay or some other blending mode, and adjusting the opacity; i think this effect feels much more natural. I still use curves for tweaks, just by adjusting the curve manually; never use presets. One of the most useful things curves does for me is the ability to adjust the colour channels separately. I use this feature a lot, usually to tone my images, especially the shadow detail (i like to add a nice subtle blue tone to the shadows of my colour images).
07/10/2012 09:05:13 AM · #3
Originally posted by LanndonKane:

Originally posted by vawendy:

Ok -- this will probably fall flat, but I thought it was worth a try.

It seems like there's so much you can do in photoshop, yet I'm in my little rut of doing the same things over and over again without learning something new. So I thought about picking a topic and seeing if we can teach each other what we know.

So I thought I'd start with curves:

I have a tendency to use the presets -- linear contrast, medium contrast, and then play with the little dots (adding and subtracting them). Every once in awhile I remember the eye droppers on the left. And I've never touched the individual red, green, blue channels.

Do you use curves? Is there anything you can teach us? Wonderful tips and tricks? How do you approach it? Or does everyone just tweak the presets?


I usually use curves for contrast in basic editing, when you can't use layer blending. I prefer to adjust contrast by duplicating a layer, setting to overlay or some other blending mode, and adjusting the opacity; i think this effect feels much more natural. I still use curves for tweaks, just by adjusting the curve manually; never use presets. One of the most useful things curves does for me is the ability to adjust the colour channels separately. I use this feature a lot, usually to tone my images, especially the shadow detail (i like to add a nice subtle blue tone to the shadows of my colour images).


Interesting... I've done the layer blending, but it seems to be such a significant change. Curves seems to be more subtle. What layer blends do you use most?

07/10/2012 09:06:00 AM · #4
here's another trick i just remembered; adjusting saturation with hue/saturation kind of sucks. colours can look awful. if my image needs a saturation bump, i will play with the colour channels in curve while masking out each image area i want to adjust (for example, if a blue sky needs a stronger, deeper blue, i'll play with the red channel while masking out everything in the image except for the sky.)
07/10/2012 09:06:38 AM · #5
I am starting to understand the power of curves. Using it more and more to correct the skin tones and overall tonality of the pictures.

Easiest tip I have come across so far - if you know a grey area in your picture, sample it. Look at the info panel for RGB values and using the hand tool in individual curves box move the RGB values to neutral.

07/10/2012 09:07:31 AM · #6
Oh, I forgot -- two things about curves:

1. Don't forget that one way of doing minor adjustments on curves is to just adjust the opacity of the curve layer.
2. Also, curves might change the saturation in a way that you don't like -- you can keep the contrast but lose the saturation changes by changing the blend mode to luminosity.

(I may be using wrong terminology here -- feel to correct me at any time. :)
07/10/2012 09:07:32 AM · #7
Originally posted by vawendy:

Originally posted by LanndonKane:

Originally posted by vawendy:

Ok -- this will probably fall flat, but I thought it was worth a try.

It seems like there's so much you can do in photoshop, yet I'm in my little rut of doing the same things over and over again without learning something new. So I thought about picking a topic and seeing if we can teach each other what we know.

So I thought I'd start with curves:

I have a tendency to use the presets -- linear contrast, medium contrast, and then play with the little dots (adding and subtracting them). Every once in awhile I remember the eye droppers on the left. And I've never touched the individual red, green, blue channels.

Do you use curves? Is there anything you can teach us? Wonderful tips and tricks? How do you approach it? Or does everyone just tweak the presets?


I usually use curves for contrast in basic editing, when you can't use layer blending. I prefer to adjust contrast by duplicating a layer, setting to overlay or some other blending mode, and adjusting the opacity; i think this effect feels much more natural. I still use curves for tweaks, just by adjusting the curve manually; never use presets. One of the most useful things curves does for me is the ability to adjust the colour channels separately. I use this feature a lot, usually to tone my images, especially the shadow detail (i like to add a nice subtle blue tone to the shadows of my colour images).


Interesting... I've done the layer blending, but it seems to be such a significant change. Curves seems to be more subtle. What layer blends do you use most?


My favourite layer blend mode is multiply. you can never really use these blend modes at full opacity, the effects are too strong. multiply suits my kind of photography- i prefer dark, bold images. I like duplicating a layer, setting to multiply, and then desaturating the top layer while adjusting the opacity.
07/10/2012 09:09:49 AM · #8
Originally posted by vikas:

I am starting to understand the power of curves. Using it more and more to correct the skin tones and overall tonality of the pictures.

Easiest tip I have come across so far - if you know a grey area in your picture, sample it. Look at the info panel for RGB values and using the hand tool in individual curves box move the RGB values to neutral.


Can you be more specific on this? You've lost me with the info panel and moving the hand tool to move RGB to neutral. Sounds really useful...
07/10/2012 09:11:04 AM · #9
I will try to post some pictures explaining this - hard to explain it in words, it is super useful.

Originally posted by vawendy:

Originally posted by vikas:

I am starting to understand the power of curves. Using it more and more to correct the skin tones and overall tonality of the pictures.

Easiest tip I have come across so far - if you know a grey area in your picture, sample it. Look at the info panel for RGB values and using the hand tool in individual curves box move the RGB values to neutral.


Can you be more specific on this? You've lost me with the info panel and moving the hand tool to move RGB to neutral. Sounds really useful...
07/10/2012 09:11:29 AM · #10
Originally posted by LanndonKane:

Originally posted by vawendy:

Originally posted by LanndonKane:

Originally posted by vawendy:

Ok -- this will probably fall flat, but I thought it was worth a try.

It seems like there's so much you can do in photoshop, yet I'm in my little rut of doing the same things over and over again without learning something new. So I thought about picking a topic and seeing if we can teach each other what we know.

So I thought I'd start with curves:

I have a tendency to use the presets -- linear contrast, medium contrast, and then play with the little dots (adding and subtracting them). Every once in awhile I remember the eye droppers on the left. And I've never touched the individual red, green, blue channels.

Do you use curves? Is there anything you can teach us? Wonderful tips and tricks? How do you approach it? Or does everyone just tweak the presets?


I usually use curves for contrast in basic editing, when you can't use layer blending. I prefer to adjust contrast by duplicating a layer, setting to overlay or some other blending mode, and adjusting the opacity; i think this effect feels much more natural. I still use curves for tweaks, just by adjusting the curve manually; never use presets. One of the most useful things curves does for me is the ability to adjust the colour channels separately. I use this feature a lot, usually to tone my images, especially the shadow detail (i like to add a nice subtle blue tone to the shadows of my colour images).


Interesting... I've done the layer blending, but it seems to be such a significant change. Curves seems to be more subtle. What layer blends do you use most?


My favourite layer blend mode is multiply. you can never really use these blend modes at full opacity, the effects are too strong. multiply suits my kind of photography- i prefer dark, bold images. I like duplicating a layer, setting to multiply, and then desaturating the top layer while adjusting the opacity.


I hadn't played with multiply -- I've usually tried soft light. In playing with it just now, I can see doing multiply and soft light on separate layers for some interesting effects! Cool!
07/10/2012 09:12:15 AM · #11
Originally posted by vikas:

I will try to post some pictures explaining this - hard to explain it in words, it is super useful.

Originally posted by vawendy:

Originally posted by vikas:

I am starting to understand the power of curves. Using it more and more to correct the skin tones and overall tonality of the pictures.

Easiest tip I have come across so far - if you know a grey area in your picture, sample it. Look at the info panel for RGB values and using the hand tool in individual curves box move the RGB values to neutral.


Can you be more specific on this? You've lost me with the info panel and moving the hand tool to move RGB to neutral. Sounds really useful...


I would greatly appreciate it -- it sounds great. Skin tones and overall tonality has been a problem for me, so I'm looking forward to this. Thanks!
07/10/2012 09:12:17 AM · #12
Originally posted by vawendy:

Oh, I forgot -- two things about curves:

1. Don't forget that one way of doing minor adjustments on curves is to just adjust the opacity of the curve layer.
2. Also, curves might change the saturation in a way that you don't like -- you can keep the contrast but lose the saturation changes by changing the blend mode to luminosity.

(I may be using wrong terminology here -- feel to correct me at any time. :)


wow, just tried this luminosity thing. it is great. always wondered how to get around those colour shifts. I like doding and burning, but hate dodging and burning in colour because it messes up the colours. will this luminosity thing get around that?
07/10/2012 09:15:11 AM · #13
Originally posted by LanndonKane:

Originally posted by vawendy:

Oh, I forgot -- two things about curves:

1. Don't forget that one way of doing minor adjustments on curves is to just adjust the opacity of the curve layer.
2. Also, curves might change the saturation in a way that you don't like -- you can keep the contrast but lose the saturation changes by changing the blend mode to luminosity.

(I may be using wrong terminology here -- feel to correct me at any time. :)


wow, just tried this luminosity thing. it is great. always wondered how to get around those colour shifts. I like doding and burning, but hate dodging and burning in colour because it messes up the colours. will this luminosity thing get around that?


That's a good question -- I avoid dodging and burning because I suck at it. But if you're doing it on a separate layer, I would think it would work... ?
07/10/2012 09:15:40 AM · #14
yeah just tried it, it definitely works better this way.
07/10/2012 09:22:42 AM · #15
Forgot one other thing -- you can select the lighter tones by doing CTL ALT 2 and do curves just on the lighter tones. Invert the selection to do curves on the shadows.
07/10/2012 09:26:04 AM · #16
Cool -- using the blue channel for adding a bit of blue to the shadows is pretty cool! (at least on the photo with which I was just playing. :)
07/10/2012 09:38:39 AM · #17
I like this thread. I don't have time to go play with anything now, but have 'watched' this so I can go play later.

Keep that advice coming guys!
07/10/2012 09:42:37 AM · #18
here's an example of how i use curves and layers. don't have the original shot unfortunately, had to grab this one from facebook. the muted colours are from duplicating the layer, multiplying and desaturating, while adjusting the opacity. i used curves to give the shadows an extremely subtle blue tone, most noticeable in the hair,

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07/10/2012 10:57:31 AM · #19
I don't duplicate the image layer, instead I use the Layers menu, from that I pick Adjustment, Curves. I don't know if that's what everyone else is doing or not. I like it because of the many choices it gives me. If you leave the layer blend on Normal, then it's OK for Basic editing rules, & I can always go back to the file & change it to something else later.

Long ago, I read an article that did a comparison between auto-adjustments and non-auto adjustments which demonstrated that for most images, most of the time, auto-adjustments are faster & give the same result. Ever since then I have always tried auto-adjusting color, contrast, & tone first, just to see what happens. It works very well on everything except flowers, where the results are not pleasing to my eye.

If I am working for a client, for publication, color/contrast/tone would be someone else's choice, not mine. But as long as I am working to please my own eye, then I wonder if the result may please only me & only on my monitor. That is the other reason I try auto-adjusting first.
07/10/2012 01:06:05 PM · #20
Curves are one of the most powerful tools for modifying tone,contrast and color. Especially used in conjunction with masks you can do some pretty incredible adjustments. I have some examples in the River Bend How-To article which include screenshots showing the Curves and associated masks.

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Another old example:

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One of the other uses is to color or tint images by using the Channel Mixer in Monochrome mode and then putting a Curves layer above it affecting one or more individual color channels.

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Except for Minimal Editing challenges I always use Adjustment Layers -- this makes it possible to change the settings, stack effects, and easily toggle effects on and off to compare.

I think the most important thing to remember about using Curves is that the steep part of the Curve will bring out detail, while parts of the graph which are more horizontal will tend to flatten out. I find out the range of tones in the part of the picture with the most detail, and then adjust that part of the curve to be more vertical.

Basic Curve Tutorial. There are also several in-house tutorials on using Layer Masks and on using Curves to achieve special effects -- check 'em out ...

Note that the Curves graph in Photoshop can be "reversed" from the default setting to have the darkest tones at the top-right and white at the lower-left; click on the gray scale below the graph to change the orientation.

Message edited by author 2012-07-10 13:13:51.
07/10/2012 02:09:32 PM · #21
So once you have set your B&W points, what curve do you find yourself using most often?
We think we are adjusting each image as it needs, but in totality we tends to develop a style and apply it to all our work, we just don't see it.
I used to use the compound bow curve but these days I find I seem to favor a soft S curve. Less gross color shifting more individual color tuning.
07/10/2012 02:13:42 PM · #22
Originally posted by BrennanOB:

So once you have set your B&W points, what curve do you find yourself using most often?
We think we are adjusting each image as it needs, but in totality we tends to develop a style and apply it to all our work, we just don't see it.
I used to use the compound bow curve but these days I find I seem to favor a soft S curve. Less gross color shifting more individual color tuning.


I favor a soft a soft S curve.

i have a style setup in lightroom where i apply that curve to all my images and then adjust more or less depending on how the image takes it.
07/10/2012 02:59:45 PM · #23
The really basic thing to remember about curves is that the curves dialog is a simple graphical representation of the "mapping" from a range of input values to a range of output values. The input values are on the X (bottom) axis and the output values are on the Y (left) axis. Imagine a vertical line from an input value up to the curve, then horizontally to the left to the output value.

So:
- If the curve is a straight diagonal line from lower left to upper right corner, there will be no change from input to output.
- Where the curve is adjusted to be below this diagonal line, the output values will be lower than the input
- Where the curve is adjusted to be above this line, the output values will be higher than the input

Now, it gets a little more complicated, but:
- Where the slope of the adjusted curve is less than the slope of the diagonal, contrast is reduced, and apparent saturation is reduced
- Where the slope of the adjusted curve is greater than the slope of the diagonal, contrast is increased, and apparent saturation is increased

Further:
- Moving the top-right endpoint to the left is the same thing as bringing in the white point
- Moving the bottom-left endpoint to the right is the same thing as bringing in the black point
- Moving the bottom-left up to the top-left corner and the top-right endpoint to the bottom-right corner is the same as inverting the image

And we haven't even discussed using the individual color channels! There are a lot more things that can be done with curves. As Paul stated, it is still one of the most powerful tools available. Prior to the popularity of RAW and the availability of post-hoc WB adjustment, curves is how we tweaked WB, and it works really well for that.
07/10/2012 04:34:28 PM · #24
Originally posted by kirbic:

The really basic thing to remember about curves is that the curves dialog is a simple graphical representation of the "mapping" from a range of input values to a range of output values.


If I ever create a signature for myself, this might be it! lol
07/13/2012 02:02:39 PM · #25
Has anyone ever played with tbe pencil tool in curves? I just went and made a series of horizontal lines, and it looked pretty funky.
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