PDA

View Full Version : Levels and Contrast and Curves, oh my!


Suspicious
06-06-2006, 02:43 PM
Recently I've gotten to experimenting with modifying the levels on my pictures before posting them to correct for all the lighting and underexposures and such, but I find that I tend to overcontrast a lot of them. I also haven't figured out how to use color balancing yet, so closeups come out a sort of sickly yellow in the end. Right now I have the temporary solution of running everything through Auto-color, but how do the rest of you run through this process?

bob1968m
06-06-2006, 03:07 PM
If I"m shooting flash as my primary light source I set the camera's whitebalance to flash. usually works when i'm outdoors as well using fillflash.

If i'm shooting under less controlled lighting I typically use my set of whibal cards and correct the white balance in post. Works best when shooting RAW, but there is a jpg workflow using Levels as well.

contrast is more an art as you set it till you like it. sometimes I under/overcorrect and then look at it day or hours later and think I didn't do it right and fix it.

Suspicious
06-06-2006, 03:13 PM
Unfortunately, I'm still a bit of an amateur with my mini-SLR, and I just shut off my flash all the time in favor of ambient light until I learn how to properly use it. I wonder if there's any tutorials out there about things like that.

bob1968m
06-06-2006, 03:33 PM
your other alternative is to buy a graycard and do a custom whitebalance before you start shooting. if the light changes you have to set it again under the new conditions. before i got my whibal cards I used a translucent coffee lid with decent results.

try dpforums. lots of good info there.

http://www.dpreview.com/forums/

TomodachiFriend
06-06-2006, 07:24 PM
I make sure my shot is good enough to begin with. I don't really white balance in postprocessing. If a picture comes out with some color cast, it's because I wanted it that way.

Auto-color never gives me results I like. I play with curves instead. But I don't understand why you end up with pictures that are too contrasting for your taste when you're the one in control.

Ami Yuy
06-06-2006, 07:25 PM
If you're already using Curves, then I can say a couple of things here.

Levels is a good start - just make sure to not over-clip or over adjust here. I rarely touch anything other than the end points.
Then Curves.
Then if needed, I do a slight upping of Saturation.

I use Curves for my contrast (the main RGB area) by doing some form of an S-shape using only 2 points. (Curves: 1) Sometimes smaller, sometimes bigger, sometimes not even an S, but it's a good guideline to go by. It takes some getting used to to get it figured out, but the more you play with it, the easier it gets.

Then, if the color balance is off some, I go in to the little pull down menu where RGB is (Curves: 2) and choose a color, depending on which color I'm trying to get rid of.
Red = Up to the left- red & Down to the right- cyan (teal/blue/green)
Green = Up to the left- green & Down to the right- magenta
Blue = Up to the left- blue & Down to the right- yellow

A general little off-tint is easily dealt with by adjusting the channel that best fits by just a smidge (Curves: 3).

When I have an extremely yellow tinted picture I generally play with the Blue and Red channels, adding more blue and cyan and sometimes the Green to pull any extra red out of it. Just be sure to keep it true to the actual skintones or colors of the object you were taking photos of.
DSCN7814-sidebyside.jpg shows an original and a fixed (I only did RGB curves to it)
DSCN7814-curves.jpg shows the curves adjustments I did.
That picture is an extreme case, but I figure it gets the point across well.

Suspicious
06-06-2006, 08:07 PM
Thanks Ami Yuy, that helped a lot. Right now I'm just eyeballing it when adjusting levels, so that's my main problem. I haven't really learned how to read or adjust curves, so I guess that's the next step I need to devel in.

deleriumx
06-06-2006, 11:14 PM
when using levels, hold down the Alt key while adjusting them to see it in threshold mode. this will show you what you are clipping. it will help you not to over clip ;) i use it every time!

gmontem
06-07-2006, 03:30 AM
Just keep in mind these adjustments are all subjective. Some will prefer lots of shadow detail while others love to put lots of contrast in their photos. Go with what you like.

Ollie
06-07-2006, 08:17 AM
There's a lot of tutorials online for this sort of thing. Read a number of them and see how they are similar, and how they are different. That should give you an idea of what you should be doing.

I have a somewhat laborious way of fixing colors, but it will stretch the histogram the right way (so I don't even have to bother with levels most of the time), and also rotates the color space towards something more neutral. Here's how I do it (which was taught to me by another photographer). It uses the Curves panel, which is a very useful tool.

With the Curves panel open, click on the black eyedropper and then click on the most black point in your image. Do the same with the white eyedropper for the whitest point, and then finally use the grey eyedropper to click on the most grey part of the image.

You'll redefine your white, black, and grey points, and the adjustment will rotate the colors into your newly defined points. It's non-unitary, so you'll loose information. Hence, it's probably best to do this on images which have not had any white-balancing, contrasting, or other adjustments applied automatically. In photoshop, this means importing RAWs (if that's what you shoot in) "As Shot" and with contrast set to "Linear."

But as said, this is all subjective as to how you like it. Photoshop has a number of filters specifically to give you an "incorrect" white balance to make a picture appear warmer or cooler. In fact, before digital came around, a lot of photographers intentionally skewed their development process to give different tints and so forth to their pictures by using different chemicals. Experiment, and it's right once you're happy with it.