Question for Tom-curves/levels

[Linda G]

Tom, or anyone else who can answer or give an opinion,

Curves and levels have very similar functions. How do you choose which one to use on any given image?

Thanks for the answers! I feel the room swelling with them!
:rockon:

[Igor]

Linda,
I'm more used to the PicturePublisher, which has similar fuunctions.
Both levels and curves are pretty much the same, except for curves give you endless possibilities for "super fine tuning" of your image balance. You can add lots of points to the curve and move them to adjust .
The levels are simplier, but that's what you need for everyday fast fixing of the images.

HTH.

[ianmcc]

the metaphor I like is Levels is like driving automatic, Curves is like driving stick shift,... the Curves will give you just a bit more control in the fine tune adjustments. A bit tricky to get the hang of but when you do you won't go back to Levels.

[timatwork]

I prefer using curves as they seem to have that extra depth of control over Levels.
Curves have a little more control in the shadow areas.

Tim

[KeithM]

I tend to use both...

I know I could use curves to do-it-all but my normal approach is to use levels to adjust black/white points and maybe a bit of gamma adjustment to suit ( by eye ) - then I'll use curves to fine adjust a particular tonal range as required.

I like, where possible, to have 'one layer = one adjustment' if only to keep me sane :)

Keith.

[crabby]

It's funny, I used to always use curves and almost never use levels. Now that I've gone digital it's the other way around. I use curves to make fine adjustments primarily in colors. But now with great gray balancing that is hardly ever needed. I like to use levels to adjust the black/white points because it shows where the pixels are located on the scale. Auto Levels and Auto Curves do exactly the same thing.

[Tom V]

Originally posted by KeithM
I tend to use both...

I know I could use curves to do-it-all but my normal approach is to use levels to adjust black/white points and maybe a bit of gamma adjustment to suit ( by eye ) - then I'll use curves to fine adjust a particular tonal range as required.

.... Keith.

Keith comes closest to my way of thinking. I look at LEVELS, and make adjustments if required, then goof with CURVES if I think I can improve anything.

Levels and Curves can do much of what the other does, but they do them in such different ways, that each has its advantages over the other. Levels is best for fixing an images range of tonal values. With the middle slider, you have only a very basic way of adjusting the midtones relative to the highlights and shadows. The Levels' histogram lets you see the range of values in a chart or sorts, which I find very informative. Curves, on the other hand is best for adjusting an image's tonal relationships. You can increase contrast in just certain ranges, be it just the highlights, shadows, or midtones. In curves you can adjust the tonal range like you do in Levels, but it is far less interactive, and in my opinion, far more cumbersome to do as accurately.

Sometimes, just looking at the image on a monitor can tell you if you need to make some sort of adjustment.

I first look at LEVELS to see the distribution of pixels in the histogram. If the pixel mounds go from end to end, I know that the image has pure blacks and pure whites (assuming there is at least a half-way decent color balance), I probably wont make any Levels adjustment. If however, the mound of pixels does not extend to both ends, or if there is a broad expanse of a low amount of pixels, or if their is a huge spike of pixels, I know that the exposure can be tuned up, or that some contrast can be enhanced. Sometimes I will move the middle LEVELS slider to brighten or darken the midtones. The only times I use the bottom output sliders is when the highlights are totally blown out, and I want some fake tone, or if I am manually adjusting for dot gain when the image is going to be printed on newspaper stock.

After I've gotten Levels the way I want them, I move to Curves. Curves gives you far more control over fine tuning contrast, brightness, compared to Levels. I would love to do all my exposure adjustments in Curves, but it doesn't have a histogram.

The Curves palette shows you a chart. Along the bottom axis is the input value, and the vertical axis is the output level. The default straight line (still considered a "curve") shows that, for example, any 43% gray value will output at 43% gray. Move the line up, and the pixels worth 43% value might print out at 62%, effectively darkening the whole image. By grabbing the 43% point on the line and bending the line upward, all the midtones will get darker to some extent. The curve will be steeper at the bottom dark tones, and will be flatter near the top light tones. A steeper line means more contrast, and a flatter line means lower contrast. So by moving 43% up to 62%, you would increase shadow contrast (bringing out detail), brightening the midtones by up to 19%, and all at the expence of the highlights, which are going to loose detail.

See http://theswampbbs.com/forums/showthread.php?s=&threadid=4436 for a recent example of an image that looked dull. I looked at the histogram in Levels, and was able to quickly fix the range of tones. It needed a curve adjustment to lighten the midtones, and add contrast to the reds.

I never sharpen before using levels. Sharpening can increase the range of values (assuming you don't already have a 100% range), making adjustments to the "original" image a bit more iffy.

The absolute worst way to adjust an image is with the Brightness/Contrast sliders in the adjustments menu. You would have to be lucky, and have the right kind of lousy picture for those totally dumb adjustments to work.

I should write a tutorial, but I really should get to work now.

:beerchug:

[dartz]

for me level is brightness-gamma adjusting.
curve are colour and tone playing
:D

here i attached some example, a potraits,
in the left, images are curved to add more grey tonal to the pic.

[dartz]

Originally posted by dartz
for me level is brightness-gamma adjusting.
curve are colour and tone playing
:D

here i attached some example, a potraits,
in the left, images are curved to add more grey tonal to the pic.

correction, the right image is curved, to add more grey tonal :)