Levels VS Curves!

[BluegrassImages]

Don,
Get a hold of me, I might be able to show you something. I had to take on-line tutorials from Lynda.com for a class. If you want to learn PS and many other programs, I highly recommend it. It is boring at times, but it will show you actual usage of it right on your desktop. They are short quicktime movies you watch when you want and most are under 3 or 4 minutes at a time.

There is clearly a difference in levels and curves and reason to use each independtly, especially if you start adding contrast or color correcting.
Brent

[RoshGlamour]

I use both [img]/ubbthreads/images/graemlins/smile.gif[/img]

[shannon_fontaine]

open an image with a fair amount of skin in it, especially facial.

Open a curves level, click on the white eyedropper

click on a hotspot on the model's face, usually the point of a cheekbone or the tip of the nose

by hotspot I don't mean blown out, just the lightest dot of skin in that area

if there's any red or yellow cast to the shot it will disappear and the pic will go blue tinted or blue green

roll the opacity of that layer back to zero then start edging it up. Usually doesn't take much but watch what happens to skin

Warning: once you start doing it you'll use it a lot

Cool/weird fact: technique works easiest on white skin but works on black skin, too.

You can do it with levels or curves, but curves makes it easier to do eensy teensy tweaks in really specific sections of the picture later

hope it works/helps for someone

Shannon

[jimmyd]

i use both levels and curves but i'll admit i'm prone to using levels mostly cuz i'm lazy and cuz most of what i do ends up on the web and, IMO, the difference between the two at 72 DPI, w/web colors, is somewhat negligible.

okay, here's my trick. i dunno if it's officially sanctioned by PS afficionados, but it works for me.

select the ZOOM TOOL and press and hold down the CTRL key and SPACE BAR and hold down the LEFT-CLICK on your mouse and pull out an area around one of the subject's eyes so it's really zoomed in. now select the LEVELS TOOL and select the BLACK EYEDROPPER and find the blackest part of the eye and CLICK. This pretty much sets the BLACK LEVELS where they should be. now you can return the image to full size and adjust the WHITE LEVEL with the slider till you like what you see, or now use the trick (for setting the white levels) described by shannon fontaine in this thread. i also sometimes adjust the mid-tones to taste (which, btw, will modify color.)

[Driftwood]

After reading the latest tutorial from my favourite magazine Digital Photo Art (recommended!)

In a brief summary of levels and curves they offer the following advice:
"We recommend Levels for setting the tonal range and curves for fine tuning tones within that range."

I have tried this approach and it works for me.
First I use a levels adjustment layer and move the black and white markers close to the ends of my histogram, usually increasing contrast but ensuring I have a full range of tones from black to white in my image. I have now finished with the levels adjustment.
I used to use the mid-point slider to lighten or darken the image, but I no longer do this, having found an alternative technique which I prefer.

Now I use a new curves adjustment layer to fine tune the image contrast. (Adjustments in curves are now usually quite minor, and I can leave the end-points anchored, which seems to make it easier to me). Quoting from the magazine again "The advantage of Curves for changing contrast is that (a) you can select an anchor point at any tonal value - e.g. you could make just the very brightest tones (e.g.255-240) brighter, and all the other tones darker, and (b) you can vary the amount of adjustment for any input tonal value."

I tried out this approach, and I really like it. Personally I do the curves adjustment visually (i.e. without reference to the numbers). Haven't tried it on any glamour work yet, but I like the control I get on my landscapes and general photography.

[Gunfitr]

Create a new document in PS. Run a black to white gradient from left to right. Go to image-adjustments-posterize and set the levels at 20.

You will get an image that has 20 distinct bars that range from black to white.

Go to image adjustments levels and play with the three sliders.

Moving then back and forth sets your white point, black point (everything above and below becoming pegged at 0 or 255 respectively). The middle slider simply adjust the "breakpoint" or the 128 point.

Now cancel out of that and go to curves. Place your cursor in the middle of the curve and push it up or down.

Your end points don't vary, but you can selectively "brighten" or "darken" the midtones with a single point selection.

IF you set a couple of tick marks on the curve line and then push or pull it, you will only get major changes betweeen the tick marks.


Think of levels like the "fader" or a stereo, while curves is like an E.Q. section.

One is about balance, the other is about boosting certain frequencies.

If you hold down ALT and click inside the Curves box, but NOT on the line, it will change the "squares" to much smaller square, and to me it provides more guidance.

In real world use, I go to levels first, and adjust my end point. I then go to curves and push up the midle of the curve for a lightening of skin tones.

I then switch to the Red, Green and Blue Channels individually and use curves to make midtone color adjustments.

I rarely do multi point curve adjustments, and generally just push the middle of the curve around.

NOTE: open and image and place your cursor on the curve line.

Push it up and to the left (towards the upper left corner) and watch what it does. Undo that and re-grab the curve in the same spot and push it straight up towards the top.

The shape of the curve makes a difference, a middle hump, versus one that gradually curves up to the midpoint and then zooms over to the right makes a difference.

If you hold down ALT after making a curve adjustment and go to the "cancel" button, it turns it to "RESET" so you don't have to cancel out of the curve and re-open.

Mark

[isaiahbrink]

Generally, I use levels first after I convert the image into CYMK color and if I can't get it right there, then I'll hit the curves. I find that it is easier to color correct in CYMK color over RGB, especially after working in the electronic prepress dept. for the advertising company I work for. I've found that it gives much more accurate color representation for output, since that's what the presses use, and my home printer use as far as colors.

Isaiah Brink

[DanNV]

Thanks for the info. I tried your tip along with jimmyd's on this image, . Then added a second curves layer to play with over all contrast (anchored the ends and hte middle and pulled down the shadows a bit.) Your trick took a lot of the extra magenta out.

Dan

[RHWeiner]

[ QUOTE ]
select the ZOOM TOOL and press and hold down the CTRL key and SPACE BAR and hold down the LEFT-CLICK on your mouse

[/ QUOTE ]

JimmyD...I tried this and was wondering why go to that extent of finger gymnastics when all you have to do is zoom in first then pick the black?

[jimmyd]

that's kinda what i'm saying to do. but seems to me that simply zooming takes more more clicks than the way i just described which is holding two keys and the left click and making a small rectangle around the area you want to zoom in on. that does it all in one move.