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By Janet Matthews

19 Sep 2009

Photography is a process of recording images using the action of light on a light sensitive surface. At one time, this light receptive surface was paper, or a glass or metal plate, and later film, coated with a light-sensitive chemical emulsion. In today's world, the term photography also includes images made through the action of light on a matrix of photo-receptors, as in a digital camera. Or...a flatbed scanner.

I have been using my flatbed scanner as an alternative method of capturing images. Using a scanner as a camera is one way to approach photography in a more playful manner, as there are no "rules" to break. I have worked out some methods, which I would like to share as suggestions, not rules, to try with your scanner. Feel free to use or adapt these suggestions so that they fit your personal working style.

Flatbed scanners have a limited range of focus, so they will produce images with very shallow depth of field. The quality of light in a scanner image is quite distinctive. It will be frontal in direction with a limited range. Portions of the object(s) that lie directly on the glass will be well lit, but there is a rapid fall-off of light for portions that are above the glass. Digital post-processing can be used to make tonal adjustments, if desired.

When choosing subject matter, you will want to keep the focus and lighting issues in mind. I would not recommend placing anything that may cause scratches or anything wet on the scanner glass. You may wish to use acetate or other transparent materials to protect the glass. Some materials may cause the glass to become dirty. Flowers tend to drop a lot of pollen, for example. I keep a container of glass cleaner wipes nearby, for keeping the glass clean. You can scan with the lid up in a dark room for a black background, or add a background cover. Remember, the light falls off quickly, so even white backgrounds will darken.

If you have only used your scanner software in "Basic" mode, you will need to switch to "Advanced" or "Professional" mode. This will allow you to override the software's default settings.

- Place your subject matter on the scanner glass and make a preview scan

- Set your image type to "Color Photo (48-bit)" or "Black and White Photo (16-bit)". The names may be slightly different, depending on your scanner, but be sure to choose an image type that uses 16-bit color per channel. This will allow you to make tonal adjustments with minimal image degradation.

- Select the area that you want to scan from the preview scan.

- Set your scanning resolution so that the image will be approximately 300 ppi at the final print size. For example, if you select an area for your scan that is 1" square and you want a print that is 4" square, set the resolution to 1200 (4 x 300 = 1200).

- Set your white and black points. You will need to override your scanner's default contrast settings to do this. Your scanner's Help menu or documentation should direct you to the contrast settings menu for your scanner. Set your white point to "255" and your black point to "0" for both input and output. Your preview scan will probably look very low in contrast. The histogram will likely show most of the data bunched up near the center. That's okay. This will give you latitude to adjust the contrast later without clipping any data.

- Now you are ready to scan.

I work with Photoshop to make tonal adjustments after scanning, so the following instructions are geared to that particular software. I first make a global contrast adjustment with an adjustment layer, which I follow with a series of local adjustments, again using adjustment layers (I prefer to use adjustment layers, but there are also a variety of other methods for making global and local contrast adjustments in Photoshop):

- Add a "Levels" adjustment layer. Set the black point by clicking the black eyedropper, and then clicking on the tone that you want to be black. I usually choose the lightest tone in the "black" background. Or you could simply move the slider on the left side of the histogram to the beginning of the shadow data. Then I move the slider on the right under the histogram to the point where highlight data starts. Because this is an adjustment layer, you are not discarding any data, and can change the settings later if needed.

- Next, I look for areas that need to be lightened or darkened, or need more contrast. I add a "Curves" adjustment layer and adjust the curve for the area I am concerned about. Don't worry about how this affects the rest of the image. After clicking "OK" in the dialog box, notice that this layer has a white box linked to it in the Layers Palette. This is a layer mask. Using the Paint Bucket tool, fill this mask with black. Activate the mask by clicking on it (it will have a border around it when active) and then click in the image window with the Paint Bucket tool. The contrast adjustment will disappear from the image. Now you can use a soft, very low opacity brush to paint white into the mask over the area of concern. This will allow the adjustment layer to show only in the lightened areas of the mask. The amount of white you add to the mask determines how much of the adjustment layer will show. Continue making local adjustments in the same manner, using "Curves" adjustment layers.

I usually work in monochrome (using a "Channel Mixer" adjustment layer to change to grayscale, rather than letting the scanner determine the way that the colors convert), so color issues are not a concern for me. If you prefer to work in color, you will need to be prepared to make color corrections as well.

I encourage you to try using your scanner as a camera. You may find that this process can be another tool to use in creating images. And it can be a starting point for further experimentation. Use your scanner with an open mind and have fun.

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