Levels and Curves

[Brownbear]

I'm struggling to fully comprehend the uses and benefits of these tools, and the whens and the hows.

I have read the tutorials here, and a couple from Adobe, and I think I understand the very basics in that Curves effects the tones and the contrast, with the risk of posterization, and it also seems to degrade the photos colour/tonal range if one changes the curve drastically?

With respect to levels, I think I understand the basics that it affects brightness and contrast and the tonal range of a photo can be enhanced, but overuse is to the detriment of shadows and highlights. This tool also seems to effect the rich colours of a photo?

Can one offset the use of the above tools by increasing the vibrancy and saturation in a photo, and the highlights and the shadows?

I would like to ask if their is a simple way to think of levels and curves? And how others decide if the use of these tools will enhance their photo, versus just using the brightness, contrast, shadows and highlights tools?

Ie; is their a simpler way to look at these? And which to use on a photo, and why?

Thank you.

[Dave Humphries]

Hi Christina,

It's late here and I should be in bed, so just a limited, quick reply on one part of this complex question....

It may help to think of an image as being Black and White, with the colours 'on top' - easy to see if you just reduce the saturation to 0 in any image editor.

"vibrancy and saturation" affect only colours.

All the other things you mention affect the underlying Black and White image (and Clarity, which you didn't mention).

So the answer to "Can one offset the use of the above tools by increasing the vibrancy and saturation in a photo, and the highlights and the shadows?" is no for vibrancy and saturation, but highlights and shadows will affect the underlying Black and White.

To my simple mind, I don't need Levels and Curves, one or the other, until you/I get the hang of it - and I'm still (largely) just using Levels - plus LCE (Local Contrast Enhancement), since that helps landscape and wildlife images look sharper, but it is probably not the right tool for portrait or architectural shooters.

HTH,

[Brownbear]

Thank you Dave. Your explanation is perfect because of its simplicity. (for me)

[DanK]

Christina,

There are good explanations of the levels and curves tools on the tutorials page. I'd start with them--they will be more thorough than answers here. If there are things in the tutorials that aren't clear, folks here can try to explain them further.

Dan

[FootLoose]

Christina,
Ben Wilmore at kelby.com has the best tutorials on curves that I have seen. As he explains it, levels is a simpler form of curves. Once you master curves, you won't bother with levels.

You need to subscribe to kelby.com to view his presentations -- well worth it in my opinion -- but maybe he has something on youtube.

gr

[Manfred M]

Christina - I quite agree with Greg's thoughts on curves versus level adjustments. Its like having the levels and exposure / contrast adjustment in a single, powerful tool. I often adjust each colour channel separately; I don't think Lightroom has this feature, but Photoshop certainly does.

[pnodrog]

Christina,
Ben Wilmore at kelby.com has the best tutorials on curves that I have seen. As he explains it, levels is a simpler form of curves. Once you master curves, you won't bother with levels.

You need to subscribe to kelby.com to view his presentations -- well worth it in my opinion -- but maybe he has something on youtube.

gr

I agree in general and use curves most of the time but there are occasions when I need to make large changes on colour channels (strong colour caste etc) when I use levels to do the bulk of the changes and then use curves to refine.

[Wayland]

You can prevent the curves or levels adjustment affecting the colours by applying them as adjustment layers and setting the layer blend mode to luminosity.

In my opinion, layers and layer adjustments with their coresponding masks and blending modes are some of the most useful and powerful features of PhotoShop and similar programs. If you are not using them already you are missing out on a huge range of possibilities.

Curves is a more flexible tool than levels but you need to be very gentle with it. A little goes a long way. The "Grab" tool in the pallet was a very useful improvement and well worth learning to use.

Levels certainly seems more intuitive at first and still has it's uses for quick tweaks even after you have got to grips with curves.

[Shadowman]

Christina,

I may have steered you towards Levels adjustment for a shadow fix on one of your photos. Keep in mind that there are two sliders (input/output) levels. The input sliders makes shadows darker and highlights lighter and the output sliders does the opposite, there is also a gray point adjustment on the input slider. Whenever you make an adjustment you can see the change and correct the adjustment if you go too far.

As others have stated, Kelby is a good source for instruction on the use of these sliders, it's where I got the information, granted I normally use Elements. Very new to Lightroom and I have only seen a Curves adjustment in Lightroom.

Hope this helps!

[Steve S]

Hi christina. The curves tool and the levels tool, do the same thing. The only difference between the two, is the curves tool gives you the flexability of adjusting all points. The levels tool, will only adjust the : black, white, and midrange.

I personally like the curves tool the best. (much better control of the image )

To use the levels tool, you just drag the black and white points over to the edges of the histogram. Then adjust the midrange to your liking. How can you do this with the curves tool?..............The black point is the bottom left part of the line---slide it to the right untill it touches the histogram. The white point is the top right part of the line----slide it over untill it touches the histogram. The midrange is the very center of the line. Move the curser to the center of the line and click a point there. Now click and hold, and drag the point diagonally up or down (perpendicular to the line) to adjust the midrange. (Using the curves tool in this way, is the same as the levels tool)

Now a few things about the curves tool.


Moving the line up will brighten the image, and down will darken the image.

The slope of the line = contrast. Make the line steeper, and you increase contrast. Make it flatter, and you decrease contrast. So lets say you adjust an image as discribed above, with only the black/white/midrange. Lets say you drug the center point down a little bit to darken the midrange. What did you do to the image?.................Well, you made the line steeper by adjusting the black and white point, so this increased the overall contrast in the image. Dragging the center point down, you steepened the highlight section of the curve and flattened the shadow area of the curve. So you added more contrast to the highlights and reduced the contrast of the shadows. So by using the curves tool, it not only gives you more flexability in your adjustments, it also allows you to see where you are adding and subtracting contrast in your image.

If you want to adjust a specific point in an image, you can bring up the curves tool, then click on the point in the image, and you will see a line appear in the curves box, showing you where that point is on the line. Now all you have to do, is click a point on the line in that location and drag the line up or down to make your adjustments.


I personally use a reverse S curve. What that does ,is increases contrast in the highlights and shadows, and reduces the contrast in the midrange. (i have to use other methods to get the contrast back into the midrange)
It also darkens the highlights and brightens the shadows.



Spend some time and learn how to use the curves tool. You'll be glad you did.

[Brownbear]

Thank you to all for your very helpful and informative replies. I do keep returning to the tutorials on curves and levels on this site (the best I've seen) but I'm trying to tie all the theoretical information together in order to allow me to understand exactly what I'm doing when I'm using the curves or level tools. None of the books I have seem to cover the topic very well.

All of you seem to be able to just look at a photo and somehow know that it needs a curve or levels adjustment, and I'd like to be able to do that, too. For example if one has a photo that needs lightening, I just noticed that using the curves tool did a better job (with respect to the final look of the image) than using just the shadows, exposure and contrast tools. I expect that this has something to do with the curves tool accounting for the tones affecting contrast in the photo but I'm not sure... And with respect to levels how does one know what tones need to be brighter or not? ie; the brightness slider affects all tones but using levels affects just the tones you select, so you need to know which tones to work on before editing.

I will subscribe to Kelby.com to learn more. I have yet to learn layers and masks, but plan to do so. Thank you.

Reading all of your replies has been very helpful and have given me with a better understanding by addressing one point at a time. Sort of like mini tutorials!

Steve, thank you. your reply is lesson in itself and wonderful!

[Mike Buckley]

I would like to reiterate that Steve's post is a mini-treatise on the subject. Moreover, when you review his images and the help he has given to others that improved their images including mine, all of that is proof of the validity of everything in his post.

Wayland mentioned that using the Levels or Curves tool will affect the color if not used within an adjustment layer. For those who are using Nikon Capture NX2, which does not make use of layers, it's Level & Curves tool will also affect color. However, if you use the tool that has the same capabilities that is built into the LCH Editor (I think it is called the Master Lightness channel but don't have the software with me at the time), the color will not be affected.

Christina: You mentioned that you would like to be able to view an image and know that Levels or Curves adjustments would be helpful. When I first began post-processing images, it took me 20 minutes per image. That's because I had not developed an eye or aesthetic for the details that I wanted to produce. Once I developed my eye for all of that, post-processing became much easier and quicker. Having said that, when I recently began making images captured in my makeshift studio that were very different from any images I had made in the past, I had to develop an eye all over again for how I wanted those images to appear.

The moral to the story is that when it comes to developing your own eye, experience is everything. If you continue pursuing this stuff so doggedly, take comfort that your eye will certainly improve over time.

[Mike Buckley]

One more thought, Christina: Keep in mind that every time you release the shutter, a curve is automatically applied by the camera. In the case of your camera, the curve was decided by the engineers who designed the camera. In the case of later model cameras, custom curves determined by the photographer can be uploaded into the camera.

So, it's important to remember that when recording light, which is what a camera does, the curve must be decided upon. It's up to you to determine whether the curve applied by the camera needs to be adjusted to improve the image. Hopefully understanding the curve in this context is helpful.

[Brownbear]

Hi Mike,

Thank you so much. Yes, I think that so far I have just been focusing on capture wildlife in action and/or the personality of the critter without a vision as to what the style of my photography is or what I would like it to be, and I think that is why I'm struggling with editing so much. Until I joined Cambridge it has basically been as my camera and settings have determined.

Seeing all the photos here,trying to learn to edit and improve my photography skills, and learn a style has been a bit overwhelming... But I have learned a ton since joining Cambridge and my birds in action are improving.

I have printed Steve's mini-treatise for reference.

I have to take a step back for a while to find the time to learn more about editing, practice my photography and clean up 1000's of bad photos (that I know are not worth editing) so no more questions, except one for a while.. Simply because once a question forms in my mind I can't rest and the replies I receive here are far more informative and educational than the ones an internet search and/or books supply...

So my last (hopefully) question for a while has to do with your mention of setting the tone curve in your camera... I can in fact do this with my Nikon D80 and at one point I was trying a low contrast curve in order to achieve a soft natural look in my nature photos... But I stopped doing this because I was not sure if I liked the low contrast effect but also because someone, somewhere, at some time advised me not to play with the tone curves in my camera. ie; they can be changed by editing... But now I am thinking that maybe a better approach is to determine the style and tone curve (in camera) that I prefer because if I manage to perfect this I will not need to edit in the photo, ie; preserving the quality of the photo because any edits needed would be minimal.

Do you (and others) set the tone curves in your camera to your preference? And if yes, why? If no, why not?

Thank you.

[DanK]

If you are shooting raw, there is no reason to try to adjust contrast in the camera. It won't affect the raw image anyway, although it will affect the jpeg thumbnail on the lcd and may (depending on the software) affect how your software first renders the raw image.

Along with many others, I deliberately choose a neutral, low contrast picture style, not to affect the image (since I am shooting raw anyway), but to get the most accurate histogram. Check out this: http://www.luminous-landscape.com/tu...ht-hista.shtml.

[Brownbear]

Thank you Dan... I shoot raw and jpeg, so great to know.. Thank you for the link. It's great information and I will try this.

[Wayland]

Like Dan, I shoot RAW and aim for a file that has all the information in it, even if it might appear uninspiring as it comes out of the camera.

The image of Morte Hoe that I posted up and "Anatomised" is a case in point.

[Brownbear]

Thank you for sharing.. The image of Morte Hoe was a wonderful learning tool. Thank you for sharing.

Like Dan, I shoot RAW and aim for a file that has all the information in it, even if it might appear uninspiring as it comes out of the camera.

The image of Morte Hoe that I posted up and "Anatomised" is a case in point.

[Alandb]

As to what your "style" might be as a photographer, you might want to consider some sort of design/photo/art book/class that deals with composition. Take a look at Michael Freeman's "The Photographer's Eye: Composition and Design for Better Digital Photos". It helps to know why you are framing the picture the way you are. How are you leading the eye? Is what is happening at the edges distracting from the main elements of the picture? Do the elements within photo have a balance? You should have some idea of these issues while you are looking through the viewfinder/screen. These are then refined as you crop the image. After that, all the tonal refinements should reinforce that initial visual idea. I don't mean to preach as I am sure that there are others ways of producing good photos. You can't produce a good photo by accident. There has to be a vision that guides the creative act.

[Brownbear]

Thank you Alan, Not preachy at all. Great advice. Thank you, I will check out the book.