Learning to Use Photoshop Curves

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Doug
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Learning to Use Photoshop Curves

Post by Doug » Thu Jan 29, 2009 8:30 pm

I wrote this tutorial because I found "curves" to be one of the hardest things to learn.
==================================================================
Learning to Use Photoshop Curves.
==================================================================

If you are like me when I started using Photoshop curves it was a nightmare!

I looked at the curves screen, started clicking, pulling, stretching and very soon the image look like crap!

I will attempt to write a tutorial on what I have learned about curves to help other astroimagers.

Quick Start:
1. Open Levels, and find black/white points.
2. Use the eyedropper to anchor black/white points.
3. Find the brightest nebulosity you have in your dark image, click and anchor to curves. Use up/down arrow keys to desired levels.
4. Repeat steps on a fainter nebulosity.
5. Use repetitive curves, don’t try to stretch in a single bound!

Let’s get started with the Step By Step.

FIRST STEP.
If you don’t have your mouse wheel button set to ZOOM in and out…do this first! It makes the zooming function so much easier, and you will need to ZOOM in and out for curves.
Go to EDIT-->PREFERENCES-->GENERAL
Click the BOX next to “ZOOM WITH SCROLL WHEEL”

Step 2.
Make a new layer copy of your original image in Photoshop. If you don’t see this screen press F7 to toggle it on/off.
Image
Click, Hold, Drag and Drop on top of “Create New Layer Icon”.

Now we have a “Background Copy” we can play around with, and keep the original image as “Background” on the layers.
ps_curves_newly_created_layer.jpg
Image

Step 3.
Finding the black and white points on your image. This is a very important step for curves. The Black and White points serve as “anchor” points on the curve scale. To find black, and white points you must use LEVELS.
Click on IMAGE-->ADJUSTMENTS-->LEVELS.
You will see the levels box pop up like this:
Image
In Levels you will see a Histogram with three little sliders, black, gray, and white. We will move the BLACK, and WHITE sliders to find the darkest black on our image, and brightest white on our image.

Take the “Black Slider” and start moving it to the right. You will notice the image getting darker, and darker…pretty soon it will be completely black! Now Slide the “Black Slider” back to the left, and the VERY FIRST SPEC of LIGHT you see will be the brightest white point! Make a mental note where that first spec of light you found on the image.

CLICK CANCEL on the LEVELS screen. We don’t want to save the Levels now, all we were doing was finding the “BRIGHTEST WHITE” point on your image!

Next ZOOM IN where you saw the brightest white point on your image. Make it a DEEP ZOOM as far as you can go!
Image
Next, go back to LEVELS, and Slide the “Black Slider” again until you see the very first Spec of Light! Take your mouse over this “Spec of Light” and
HOLD the SHIFT KEY, and LEFT MOUSE CLICK. This will set the White anchor point.
Next CANCEL OUT OF LEVELS, don’t save any Levels now.
This will create a “new color sampler” or an Anchor for the “brightest white point” on your image! We will need to reference this white point later when we use CURVES.
Image

Next we need to get the “Darkest Black Point” on our image. You guessed correctly…repeat the same steps as described above, but instead of moving the Level’s “Black Slider” to the right, take the “White Slider” and move it to the left!

One thing you will need to do before you begin finding the dark point is to ZOOM OUT so you can view the entire image.

After you have successfully marked both Brightest, and Darkest point you should see something similar to the image below.
Image
Your image will have completely different white, and black points, however, most of the time it’s the brightest star, and darkest area in your image.

Now let’s get started with CURVES!
Here is NGC2264 before any curves have been applied:
Image

If you DON’T see the newly created Black, and White Points…Click the “Eye Dropper” tool.
Image

REPEAT MARKER:
Click IMAGE-->ADJUSTMENTS-->CURVES
You will see this Screen:
Image

Next ZOOM in using your SCROLL button on your mouse to the White Point. With the Eye Dropper Over the White Point “Hold the Ctrl Key” and “Left Mouse Click” the Whitest point. This will create a Black square on the Curve line.
Image

Next we need to make an Anchor point for the black point.
ZOOM OUT with the Curves Dialog box still open, and find your dark point, and ZOOM in on your dark point.
Image

After you have set your black and white points on the curve line you should see something like this:
Image
Setting your Black, and White points on the curve line PREVENTS you from pulling or stretching the image out of bounds.

With the Black and White Points Set, next take your Eye Dropper Tool, and find the brightest nebula (or faint star dust) you can see. Once you find a part of the image that is BETWEEN the BLACK, and WHITE points Hold “CTRL” and “Left Click” the mouse. Then use the UP ARROW KEY to bring up the details.
Image

Here is an example of using the UP arrow key to pull the curve up:
Image

Original Image:
Image

After 1st Curve:
Image
You will not see much of a difference from the first iteration of curves. But you will start to see some details appearing.
Now, go back to the REPEAT MARKER: above, and Open up the Curves window, anchor your Black, and White Points on the Curve Line…then Find an area on your image to Pull UP with the Arrow keys.

Second iteration of curves:
Image

Third Iteration of Curves:
Image

Fourth Iteration of Curves:
Image

We started with this:
Image
And after 4 iterations of Curves we ended up with this:
Image

Final processed image with MORE than 4 iterations of curves!
Image

Other Helpful Notes About Curves:
When in the “CURVES” window you can move to each “Black Square” on the “Curve Line” by Pressing “CTRL + TAB”. This will cycle through each “Black Square”.

AVOID USING THE MOUSE ON THE CURVE LINE!
Start using the mouse on the “Curve Line” and your image will get wildly out of control. USE THE ARROW KEYS! MOSTLY USE UP AND DOWN ARROW KEYS, but you can use left and right arrow keys too. This tutorial only used the UP arrow key.

If you don’t like the Curve settings you made while you are still in the “Curves Window” Hold the “ALT” key, and the “CANCEL” button turns into a “RESET” button! Huge help!

SMALL Incremental Steps with Curves! You will need Multiple iterations of curves!

NEVER CLIP YOUR CURVE DATA LIKE THIS:
Image

I hope this tutorial was helpful, and if anyone knows a better way…please share!

Thanks,

Doug
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Re: Learning to Use Photoshop Curves

Post by rray6 » Sat Feb 07, 2009 8:43 am

Doug,
I'll admit that PS Curves are 'hit and miss' with me. Have you finished the step-by-step yet? Looking forward to it.

Robert
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Re: Learning to Use Photoshop Curves

Post by MikeM » Sat Feb 07, 2009 9:05 am

Great idea! I too kinda wing it with Curves without really knowing what I'm doing.
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Re: Learning to Use Photoshop Curves

Post by Doug » Sat Feb 07, 2009 9:10 am

My photoshop curves tutorial is about 50% done right now. I am writing it in Word, and I have many examples of images during the tutorial to help make things clear. Once I complete the tutorial in Word, I'll copy and paste the entire tutorial here.

I am glad I wasn't the only one who thought curves were difficult to learn!

Doug
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Re: Learning to Use Photoshop Curves

Post by rray6 » Sun Feb 08, 2009 9:05 am

Can't wait! Your other tutorials (RGB for instance) have been great. Thanks.

Robert
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Re: Learning to Use Photoshop Curves

Post by Doug » Wed Feb 25, 2009 11:34 pm

rray6 wrote:Can't wait! Your other tutorials (RGB for instance) have been great. Thanks.

Robert
Ok, I drafted the first round and place it up here! Please let me know if you think this tutorial was helpful.

Doug
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Re: Learning to Use Photoshop Curves

Post by toddbenko » Thu Apr 16, 2009 8:22 pm

Doug wrote:
rray6 wrote:Can't wait! Your other tutorials (RGB for instance) have been great. Thanks.

Robert
Ok, I drafted the first round and place it up here! Please let me know if you think this tutorial was helpful.

Doug
Doug

I wondering where you posted it up here. I've looked all over the thread and up in other areas of the forum. I don't see the word version of the tutorial? :what: Am I missing something?

Todd

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Re: Learning to Use Photoshop Curves

Post by Doug » Thu Apr 16, 2009 9:02 pm

Hi Todd,

I drafted the tutorial in Word, and transformed it into a Forum format. If you want a version in Word PM me, and I'll email you a copy.

BTW, Welcome aboard! :thumbup:

Enter our monthly imaging contest!

Doug
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Re: Learning to Use Photoshop Curves

Post by Doug » Thu Apr 16, 2009 9:21 pm

Todd,

I looked up your email address on your account, and emailed you a Word copy...this was a draft, so it might be a bit different.

Let us know if you can't find something, and we'll find an answer. If it's not here, maybe we need a tutorial! Your welcomed to write any tutorial here.

Doug
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EJD

Re: Learning to Use Photoshop Curves

Post by EJD » Tue Apr 21, 2009 8:23 am

Quick question on finding the black point while in Levels. I understand the white point part (moving the black slider to the left until the first light appears) but when it comes to the other end as I'm moving the white slider back to the right what am I looking for?

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Re: Learning to Use Photoshop Curves

Post by Doug » Tue Apr 21, 2009 11:16 am

EJD wrote:Quick question on finding the black point while in Levels. I understand the white point part (moving the black slider to the left until the first light appears) but when it comes to the other end as I'm moving the white slider back to the right what am I looking for?
Hi EJD, and Welcome Aboard!

The slider bars to find the black point is moved until the screen is pure white, and then start sliding the knob until you see the first hint of any image starting to appear. When you start by sliding until you see a WHITE screen, then the very first hint of any image is the DARKEST point on your image.

I'll try to post some examples later tonight.

Doug
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Re: Learning to Use Photoshop Curves

Post by MikeM » Thu Apr 23, 2009 6:37 pm

I'm going to have to give this a try. Thanks.
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Re: Learning to Use Photoshop Curves

Post by Norm » Mon Apr 27, 2009 3:27 pm

Hello Doug,

This is a great tutorial. I find that Photoshop is very complicated and I really appreciate the way that you have simplified the "Curves" system.

Thanks for your efforts.
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Re: Learning to Use Photoshop Curves

Post by Doug » Mon Apr 27, 2009 3:41 pm

Hi Norm!

Welcome aboard! :clearsky:

I am glad you found the tutorial useful. We maybe a small group here, but lots of helpful people. Don't hesitate to ask questions, or if you would like to share some processing tricks post'em here!

Take a few photos, and enter our monthly imaging contest too!

Doug
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Re: Learning to Use Photoshop Curves

Post by Norm » Mon Apr 27, 2009 3:46 pm

Hi Doug,

Thanks for the welcome. As I am new to this forum, I do not know if my private message to you went through. I had asked that you please send me a copy of your PS Curves turorial in the "Word" format.

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Re: Learning to Use Photoshop Curves

Post by Doug » Mon Apr 27, 2009 4:21 pm

Hi Norm,

I'll email it to you later tonight. :thumbup:

Doug
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Re: Learning to Use Photoshop Curves

Post by Doug » Mon Dec 14, 2009 4:10 pm

I noticed this tutorial is being linked as a reference from other websites! I am happy other people are finding this useful.

The tutorial in this forum, while good, is outdated. I have received more suggestions from other people, and have added their suggestions here:
http://myastroimages.com/Astro_Imaging_ ... op_Curves/

Thanks!

Doug
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Re: Learning to Use Photoshop Curves

Post by MikeM » Mon Dec 14, 2009 8:08 pm

That's a great tutorial Doug. since you posted it I use it quite often. Thanks!
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Re: Learning to Use Photoshop Curves

Post by gregpoulsen » Tue Apr 16, 2019 9:47 am

Hi there
Many thanks to author. Good job.
By the way, I'd like to provide you fresh information about Adobe PS element.
This information must be so useful for sure.
http://fixthephoto.com/photoshop-elements-free.html
Cheers

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Re: Learning to Use Photoshop Curves

Post by Doug » Tue Apr 16, 2019 7:29 pm

Hi Greg,

Welcome to the forums. If I remember correctly, I don't think Elements will do curves. Does elements now support curves?

Doug
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