PS Curves questions...

Unbrok3n

So after reading the "making your photos pop" tutorial, I've been experimenting with curves. I dont have many "dull" iamges, but curves seems to help out a lot with everything! Now, I have really no idea what I'm doing. Just making s's and seeing what looks good.
Could someone lead me to somewhere (or quickly do it yourself) that could give me a rundown of curves?
What is the gray area in the background? Is the lower half contrast? Is there a way to just raise the contrast of a certain part without points?
And many more questions...
Sorry for only asking questions...and thanks so much for any help!

jsmiley

Unbrok3n wrote:

So after reading the "making your photos pop" tutorial, I've been experimenting with curves. I dont have many "dull" iamges, but curves seems to help out a lot with everything! Now, I have really no idea what I'm doing. Just making s's and seeing what looks good.
Could someone lead me to somewhere (or quickly do it yourself) that could give me a rundown of curves?
What is the gray area in the background? Is the lower half contrast? Is there a way to just raise the contrast of a certain part without points?
And many more questions...
Sorry for only asking questions...and thanks so much for any help!

Zack
Check this out.. http://dgrin.smugmug.com/gallery/1865354
and you can search photo shop for a tutorial

BinaryFx

Unbrok3n wrote:

Could someone lead me to somewhere (or quickly do it yourself) that could give me a rundown of curves?

http://members.ozemail.com.au/~binaryfx/links.html#C - Scroll down to curves!

Start here:

http://www.gurusnetwork.com/tutorial/curves/
http://www.ledet.com/margulis/Makeready/MA21-Defanging.pdf
http://www.biomedstudio.com/CorrectByNumbers.pdf (http://www.jkost.com)
http://www.eddietapp.com/PDFs/ccmethod_cs.pdf


Then graduate to:

http://www.ledet.com/margulis/PLC_Ch02.pdf (free full chapter)
http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf (free full chapter)


Hope this helps,

Stephen Marsh
http://members.ozemail.com.au/~binaryfx/

Unbrok3n

Thanks, I'll give it a try

I tried some very moderate curving with the "tanzania" galleries on my website. If somebody has some time could you tell me if they look decent or not? (they are also taken with an old p&s and not with my d80, but its the pp im worried about

thanksss!

Unbrok3n

The first link was really great! Is it OK that these tutorials are all for much older versions of photoshop? Is there anything for CS2 or CS3?
Thanks!

BinaryFx wrote:

http://members.ozemail.com.au/~binaryfx/links.html#C - Scroll down to curves!

Start here:

http://www.gurusnetwork.com/tutorial/curves/
http://www.ledet.com/margulis/Makeready/MA21-Defanging.pdf
http://www.biomedstudio.com/CorrectByNumbers.pdf (http://www.jkost.com)
http://www.eddietapp.com/PDFs/ccmethod_cs.pdf


Then graduate to:

http://www.ledet.com/margulis/PLC_Ch02.pdf (free full chapter)
http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf (free full chapter)


Hope this helps,

Stephen Marsh
http://members.ozemail.com.au/~binaryfx/

pathfinder

The basic techniques for using curves to adjust images has not really changed in CS, CS2 or CS3. The panel for CS3 looks a little different, but basically adjusts the image the same way.

BinaryFx

Unbrok3n wrote:

The first link was really great! Is it OK that these tutorials are all for much older versions of photoshop? Is there anything for CS2 or CS3?
Thanks!

I agree with Pathfinder.

Apart from cosmetic GUI touches, the basic underlying approach of remapping an input value to an output value has not changed - curves still basically generally work the same in later versions of Photoshop compared to earlier ones.


Stephen Marsh
http://members.ozemail.com.au/~binaryfx/

Unbrok3n

OK, good
Now I just have to get learning!

Unbrok3n

Im trying to get the basics of curves here.
So if I want to bring out a certain part of a picture, (im practicing with a pic I have of a red and black bug on a green leaf) I want to find the highs and lows of the "centerpiece" and curve between those 2 points? I ctrl clicked on the light and dark spots on the bug (the light point os made was in the middle of the curves line, and the dark was towards the bottom) then I made a slight s curve. It made it look a lot better, but just so I understand, was that focusing only on the bug since those were the points I created?
Sorry, I probably sound like an idiot.

Unbrok3n

The thing thats confusing, is in most of the tutorials, and what ive seen, after all is said and done, it looks like you could have gotten the same effect with using the contrast bar!

Unbrok3n

Here are 2 examples. Both originals are on my site (actually in my slideshow as well) and here is my attempts at curves with them. Please give me harsh c&c. I dont really know what im doing, so these were educated guesses mixed with what I thought looked good.
Once again, it mostly looks like just a contrast boost. What am I missing?

pathfinder

Steepening a curve will increase the contrast, in the area of increased steepness. Curves are a much more accurate and controlled tool than the Contrast slider which is one of the crudest tools in Photoshop, and most people recommend not using the Contrast sliders at all. If you change the curve in only one channel, you can alter the color balance as well, in selected areas of the image.

Unbrok3n

Ya, after some more reading I realized why the contrast slider is a no-no. haha

pathfinder wrote:

Steepening a curve will increase the contrast, in the area of increased steepness. Curves are a much more accurate and controlled tool than the Contrast slider which is one of the crudest tools in Photoshop, and most people recommend not using the Contrast sliders at all. If you change the curve in only one channel, you can alter the color balance as well, in selected areas of the image.

Unbrok3n

OK, I have a question (not sure anyone is still reading this thread)
But anyway,
Ive gone through a couple basic tutorials by now on curves and setting the shadows and highlights, and Im confused on which levels for RGB to use.
For example, on the "popping" tutor here on Dgrin the poster sugessts 7 7 7 for black and 247 247 247 for white(rgb) and in Scott Kelby's CS2 book for Digital Photographers he suggests 20 20 20 for black and 244 244 244 for white. I understand they are different shots ( a portrait and a colorful lights at a carnival) but how do you when to change the values? The pop articles says to default those settings. SHould you always use the same calues for black and white when setting your points?
I hope someone can explain this. Thanks

pathfinder

The amounts to set for your default setting for a black and a white point, relate to how ink is displayed on paper. It is very difficult to see much difference between 2,2,2 and 4, 4, 4 so most folks use 5,5,5 or a similar amount for a black point. Similarly, once the ink is light enough on the paper, you really can't see much difference so folks tend to use values of 248, 248, 248 or thereabouts. Different gurus may recommend different nunbers, but there is not really a right answer, but a set of right answers.

Personally, mine are set at 5,5,5 and 248,248,248. You could probably use higher numbers for a black point when printing on matter paper, rather than glossy, as matte paper prints to a lesser Dmax value, a less deep, dark black. Part of the nature of matte versus glossy paper.

Unbrok3n

So setting those points is only for printing?
I asked this question in another forum and someone said this:

It has long been argued that those settings are incorrect because they don't exploit the full gamut of the monitor. And unless you're specifically preparing photos for printing there's no need to modify the black and white clipping points as in your example.
See this thread; especially the contributions by Thomas Niemann: http://forums.dpreview.com/forums/read.asp?forum=1006&message=25629602
Or better yet, go to his site at http://www.epaperpress.com/psphoto/index.html and click on Color Correction > Black/White and see what he has to say.
If I'm not mistaken some of the more recent Photoshop book like Photoshop CS3 Studio Techniques by Ben Willmore omit this advice on remapping clipping points.



Now I'm just completely confused. Isnt the point of setting the black and white to get the full tonal range of the picture? Should I do it with every picture? Somebody help. Sorry, I just want to make sure im learning correctly.

pathfinder wrote:

The amounts to set for your default setting for a black and a white point, relate to how ink is displayed on paper. It is very difficult to see much difference between 2,2,2 and 4, 4, 4 so most folks use 5,5,5 or a similar amount for a black point. Similarly, once the ink is light enough on the paper, you really can't see much difference so folks tend to use values of 248, 248, 248 or thereabouts. Different gurus may recommend different nunbers, but there is not really a right answer, but a set of right answers.

Personally, mine are set at 5,5,5 and 248,248,248. You could probably use higher numbers for a black point when printing on matter paper, rather than glossy, as matte paper prints to a lesser Dmax value, a less deep, dark black. Part of the nature of matte versus glossy paper.

colourbox

Note that the Brightness and Contrast sliders are not as destructive in CS3 as they used to be. The default now is to not clip. In CS3 they work more like Brightness and Contrast in ACR/Lightroom. If you want them to clip like they used to, you turn on the Use Legacy checkbox in there.

The new behavior means it's much safer to yank the Brightness and Contrast sliders around without clipping the heck out of your image. It's still one of the cruder tools and we should all stick with Curves, but at least they will no longer mercilessly wreck the images of newbies who try them first.

BinaryFx

Unbrok3n wrote:

Now I'm just completely confused. Isnt the point of setting the black and white to get the full tonal range of the picture?

When one sets the black/white endpoints, one is usually setting range and altering colour balance in one step.

The original image may have a casted shadow of say 15r 12g 16b, setting the black point at an idealised neutral R=G=B value of say 10r 10g 10b will extend the tonal range as well as affect the original colour balance. Usually this is a good thing, however there will also be exceptions.

The white point is similar.

So, there are three general goals when adjusting the tonal range of an image. 1 - Change tone and colour balance with the one curve operation (usually to each individual channel, ignoring the master/composite curve). 2 - Change tone without affecting hue. 3 - Change hue/saturation without affecting tone.

Should I do it with every picture? Somebody help. Sorry, I just want to make sure im learning correctly.

Not every image will require endpoint adjustments, it would be crazy to force an image to the extremes if it did not benefit from the move. Some images may require adjustment of tonal range - but not colour balance (luminosity blend mode curves). Some may require adjustment of colour balance, but not range (color blend mode curves). Some may require separate luminosity and colour curves instead of a single normal blend mode curve.

It is not always so much about the extreme (or near to) darkest and lightest areas of the image - but more so the darkest and lightest areas of the image that contain detail or that are more critical to the observer than areas of lesser importance (targeting the curve moves to the content, rather than to the darkest/lightest areas).

The questions that you are now asking go beyond the basics, to more advanced. I would suggest my earlier link to these two resources:

http://www.ledet.com/margulis/Makeready/MA21-Defanging.pdf
http://www.ledet.com/margulis/PP7_Ch02_ByTheNumbers.pdf

The second link is an entire free chapter, the preceding first chapter in the book goes into your questions of the why/when of image editing.

P.S. When posting images for review of your edits, it would be helpful to see the original, as well as the edited image on the same page.


Sincerely,

Stephen Marsh
http://members.ozemail.com.au/~binaryfx/