Digital Imaging

by PhotoMann

Today's technology does however provide powerful tools for imaging with computers. It has allowed me to merge my favorite hobby (photography) and my profession (computer engineering). My principal goals are to have a digital reference/database of my images and to produce video slide shows (VSS) to share my images with friends. As long as my "spare" time permits the production of this newsletter is relatively easy given the tools/toys at my disposal. All of my original images are still on traditional film (mostly slides). Utilizing a Nikon Coolscan (current street price $1400) I can scan 35mm slides or negatives at resolutions up to 2700 dots per inch (dpi) which is roughly the same as a photo-CD. 2700 dpi produces enough data to produce an adequate 8x10 print. It would be nice in theory to scan all images at maximum resolution but practicality dictates otherwise. A scan at maximum resolution with the Coolscan can take 10-13 minutes and produces a 25 megabyte Windows bitmap file. My patience and disk space would vanish quickly doing this. For my current requirements I generally scan at 300-600dpi depending on the cropping of the original image. The files are typically 400-700k bytes.

Producing VSSs is my primary activity since scanning all my images to produce a comprehensive reference is a pipe dream. The first step in creating a VSS is just as hard as creating a traditional slide show. You have to edit your images down to the select few you want to show the world. Once this is done then the scanning process can start. This is by far the most time consuming part. I limit my scans to 300-600dpi due to the limitations of my final output medium (video). Using the Nikon Coolscan the prescan, exposure adjustment, cropping and final scan can take roughly 5-7 minutes per slide once you have mastered the process. I have my eye on a Polaroid Sprint Scan which will considerably reduce the time required but it will put a big hole in my pocket. I'll have to sell my Coolscan before I can justify buying the Sprint Scan.

The Nikon Scanner Control window seen on the first page shows the interface used to acquire the digital images. Once the slide is put in the scanner the preview button is pushed to get a low resolution image to work with. The preview is used to adjust the scanner controls until you see the results desired in the final scan. Numerical factors for brightness and contrast as well as for red, green and blue can be specified but I primarily use the gamma curve control. It's the button with a curve on it. Gamma is the measure of contrast in photographic images. The curve shown is adjusted for the most accurate control of red, green and blue exposures. I generally use the master curve which is a combination of red, green and blue. If color correction is required it's easier to do it later in Adobe Photoshop. Adjusting the gamma curve to obtain optimal scans can be frustrating until you gain experience with it. It's almost like black magic at first. Cropping for the desired final image is the last step prior to scanning.

The next step in producing a VSS is to touch up the images using Adobe Photoshop. Photoshop is the most comprehensive tool for working on digital images. It's basically an electronic darkroom plus much, much more. The scanner controls allowed me to produce an acceptable image but Photoshop is the tool for refining it for final presentation. I typically do minor exposure adjustments and sharpen the images slightly.