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Fall 2007 Archive
Photojournalism
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For those who have done film, you know that taking the shot is just step 1 in making a photo. While most people would drop their rolls of film off at a lab and pick up the prints, similar to how digital photographers simply take the image file that comes out of their camera and starts posting it to facebook, images from film or digital can be radically modified and made better by processing them yourself, either in the darkroom or with an image editing application.
We'll first focus on how to manipulate brightness with software. There are lots of ways to do this - most of you have probably seen a "brightness" slider in most basic image editing apps. One of the most versatile and powerful ways to adjust exposure is via a tool called "Curves". In Adobe Photoshop, which I'll be using for these examples, the tool can be found under Image->Adjustments->Curves. Here's the image we'll start out with:
When we open up the curves tool, we get a diagonal line - this is the "curve" that we will be manipulating. For those who have Adobe Photoshop CS3, you'll also see a graph behind it - this is the "histogram", which represents all of the pixels in the image and plots them according to their brightness (towards the right is the number of bright pixels, and towards the left is the number of dark).
We can make adjustments to this curve, which will change the brightness of the image. By lifting the entire curve up, for example, the whole image gets brighter, much like if we just moved the brightness slider up on any other program.
Mouse over the image to see the changes
If we wanted to make the image darker, we'd just pull the curve downwards. Now observe what happens when we lift the curve up, but only on the rightmost portion. You can set points by simply clicking along the curve, and dragging the points to a new position.
When we lift the curve up, the image gets brighter, but only for those pixels that are in the region where the curve was lifted. Since our curve was raised mostly on the rightmost portion, the bright pixels became much brighter, but the pixels that were dark remained about the same. The same thing happens if we lift the curve up for only the leftmost portion (dark pixels):
This selective processing of images is where the power of curves come in. With a regular brightness slider, we only get two options: make the image darker, or make the image brighter. With curves however, we can adjust brightness levels individually for different portions of the image (based on original pixel brightness). Thus instead of results like this (everything brightened the same):
We can achieve images like this (only the dark pixels brightened):
Another powerful use of curves is enhancing contrast - making dark things darker and bright things brighter. We can achieve this by lifting the curve up on the right side (making bright pixels brighter), but pushing the curve down on the left side (making the dark pixels darker). This achieves a result like this:
Take care not to overdo this and change the curve too drastically, however, because this will clip the brights to pure white and the darks to pure black, destroying detail. You can tell if the curve is doing this by making sure the curve is not "flatlining" towards the right and left, like it's doing here:
This week's assignment is to take one of your photos (from a previous assignment, or shoot a new one), and use curves to adjust the brightness and the contrast. Post the before and after results, and if possible, see if you can take a screenshot of how your curve looks like.
Curves are found in Adobe Photoshop, Adobe Lightroom, and other more advanced image editing applications (not sure about Elements or Aperture). For those of you who don't have an advanced image editing program, I'd recommend you try downloading GIMP (GNU Image Manipulation Program), a free open-source image editing program that is much more powerful than your average Picasa or iPhoto and has many of the same tools as Photoshop, although in my opinion it's not as intuitive and a bit harder to use. You can download GIMP here:
Windows download: http://gimp-win.sourceforge.net/stable.html
Mac download: http://darwingimp.sourceforge.net/download.html