Curves

Bonus blog post...

Basically, we haven't discussed it much yet but the Curves adjustment tool is a great way to adjust tone and color (and therefore exposure) ranges throughout a photo all in one convenient place. Very useful. See Photoshop menu Image --> Adjustments --> Curves or for similar processes in GIMP try menu Colors --> Curves.

There's an extremely clear and understandable tutorial about how to use Curves over at Tutorial9.net

Curves can be overdone with great ease... but they can also be a convenient way to tweak a lot of color and value settings all at once. And if you want very subtle control using layers options like 'lighten' or 'darken' or 'luminosity' or 'hue' with some transparencies too, try using Curves in a new Layer, or Adjustment Layer. (actually the same is true with any of the processing controls we've tried throughout this class).

Visual example of the differences... using curves to fix the tonal range in the shadows and midtones...

Understanding Color: Part 2, Light Sources and White Balance

We photographers depend on the presence and absence of light to create our images.

But all light is not the same.Every light source has an average color range. Moonlight is a different color than sunlight. Incandescent light bulbs are warmer than most fluorescent light bulbs. Light from a candle is significantly yellower than light from most LED flashlights, which are often kind of bluish.

You can respond to and control your relationship with the light by adjusting the White Balance of your camera. Selecting a correct White Balance will leave the neutrals neutral. In other words, the photo will look a lot like what you see with your own two eyes. This is usually our goal: match the white balance settings of our cameras to the color temperature that we really see in the world. To say that what you’ve photographed looks like what you see with your eyes, that the white balance is matched, is to say that the photo is ‘color accurate’ or 'color correct.'

If you haven’t set your White Balance controls for the lighting you’re using for your photo, then you may end up with neutral areas of a photo appearing too vivid or unusually colorful. This is often an accident, but you could adjust the White Balance for artistic effects… if the colors are more vivid than what you can see, then you must be being an expressive artist – same if they are highly desaturated, or mainly grayscale (which isn’t like what we see in the world but can be very beautiful). Selecting the right White Balance for your artistic needs is the first step towards being more artistic with your use of Light, and being able to select the kind of artistry that you’d like to be rather than making images by default of whatever automatic settings are used by your camera.

How light is defined: Light is defined by it’s Color Temperature. For example, bright daylight is defined as 5500k, whereas the flash of your camera may have a temperature of 5400k, an incandescent light bulb 3,000k, a Fluorescent light bulb at 4200k, a cloudy day might be 6,000k and in shade, perhaps 7,000k or even 8,000k if it’s foggy. The ‘k’ stands for the Kelvin Temperature Range (if you want to read all about using the Kelvin to measure color temperatures, black-body radiators, etc., then click here: http://en.wikipedia.org/wiki/Color_temperature). It used to be that you had to select a particular kind of film to match the color temperature, for example, using a Tungsten film if you had hot halogen lighting in the studio, or Fujichrome film if you wanted vivid outdoor action photos. Instead of having to swap out the film to match the lighting, today’s digital cameras have a button. The button alters a series of settings that you can use to match your White Balance with the lighting in the world around you.

In a Nikon digital SLR, there’s just a little button on the top of the camera, marked WB, and you can scroll through some settings easily.With many non-SLR cameras, you may find a menu screen full of 'scenes' such as Snow, Candle, Sunlight, Landscape, Portrait, Cloudy, etc. Each of these is likely changing the white balance to compensate for the typical color temperatures found in each kind of scene.

So here’s your mini-assignment: take a set of pictures of the same object or person, but using different white balance settings. It's easiest to see the differences if you use an object that is light in value. Then cut and paste the pictures to make a composition like this one:

Use the text tool so that to label what kind of light source you’re using, and then label each image for how you changed the white balance in your camera. As a result you now have a composite Reference Photo that you can rely on to compare and contrast with while you make images – do you need to make an image feel warmer, when using an indoors fluorescent light source? Then shift the white balance to Daylight or Flash. Do you need it cooler and more mysterious? Then shift the wb to Incandescent... and so on.

Label and submit your composite image to our shared Picasa album. 

Understanding Color: Part 1 Basic Terms and Concepts

Color terms: Hue Saturation Value

Hue: the name of the color (or in digital photo, the numbers) Red, Orange, Yellow, Green, Blue, Indigo, Violet

Saturation: the brightness or chroma of the color, how much grey versus how much pure hue. Especially vivid colors tend to be highly saturated.

Value: the lightness and darkness of the hue. A black-and-white photo uses no hue, and only relies on value.

Warm vs. Cool Colors: a Warm Color is in the red-orange-yellow range, such as fire. a Cool Color is in the blue-green-black range. For example, the right block is said to be cooler than the left warm gray:

RGB and CMYK. Cameras and printers rely mainly on RGB (Red Green Blue) systems to describe color, and sometimes on CMYK (Cyan, Magenta, Yellow, and Black). RGB refers to what happens when you mix Red, Green, and Blue lights together. If you look closely at the pixels on your computer monitor, you’ll see that they are tiny groups of red green and blue dots. CMYK is mainly used as a color model for printing colors, and is increasingly uncommon.   

RGB Color and How to Number the Colors. Each range of Hue in this model is assigned a number, usually from 0-255. So, zero Red and zero Green and zero Blue combined – no color at all – equals black, where 255 Red and 255 Green and 255 Blue is white. All the other colors are a range between these extremes. Check out the numbers within this menu box, which is the 'Color Picker' (the little eyedropper tool), from Photoshop:

               

You can of course move the slider arrows up and down, and see how the numbers move along with you through the spectrum. If you click on 'only web colors' then you'd see a chunky chart showing a more limited range of colors. In GIMP these controls are similar.[if you'd like to learn a lot more about RGB color, then click here: http://en.wikipedia.org/wiki/RGB_color_model ]

Here is probably the easiest way to change all of the colors in your photo at one time: the Hue/Saturation control (under Photoshop menu Image -> Adjustments -> Hue/Saturation)

The image unchanged, from a photo of a sun dog:

The image altered severely with the H/S controls, same photo:

This is now extremely saturated, the Hue was shifted down, and the image was darkened. For almost all photos, I find that I rarely alter the Hue, and tend to use the LEVELS controls for lightness/darkness. Thus this control is used mainly for saturation, about which I find that increasing the saturation above the number 18 is just way too much for naturalism, and becomes expressionistic instead.

Another basic color control is the Color Balance menu. (in Photoshop it's under Image --> Adjustments --> Color Balance). It looks like this:

Here I simply slid the balance far more into the red, making the entire image a lot pinker. If you're curious, here is the photo I was toying with to show you these color controls. I hope you'll agree that it's a pretty picture:

Watch for sun dogs like this in the Berkshires... they happen here all the time thanks to the mountains, the moisture in the air, and the angle of the sun at sunrise and sunset.

As far as thinking about color goes, I think it's good to keep in mind the variables involved. Some basic Color Design Questions can be

-          (Value) Should this image, or part of it, be Lighter or Darker?

-          (Hue) Should this image or part of it be Warmer or Cooler?

-          (Saturation) Should this image or part of it be More Vivid or More Grey?

Some Simple Ways to Alter Color Relationships:

-          Levels (you already know about this... and maybe you also found the Color Histogram)

-          Hue/Saturation control (the best!!)

-       Color Balance control
-       Apply Color Photo Filter (easy)

-          Create a new Layer, Paint it with a color, and then set the Layer to mainly transparent (fun)