Congratulations on having your legacy family photo collection duplicated to digital with the finest precision known to man! The art of duplication is so much more than duplicating from the photonic domain into the digital. The first thing that comes to mind regarding duplication to digital of slides and photos is the image quality—and that with good reason. Below I shall discuss some of the important issues in that regard but let us not forget that there is the human perspective of optimizing the viewing experience as well.
THE BIG PICTURE:
Our scanning process is much more than meets the eye. We do not scan the slide once. Each slide is scanned THREE times. The first scan is simply an image scan. The second scan is an infrared scan that maps any microscopic debris. The third and final scan is taken at a brightness different from the first. The first and third images are then blended together with a net effect of increasing the dynamic range (discussed below). And lastly, the image file created by the scanner is a 64-bit image. 48 of the bits is image information. The remaining bits are machine information holding relating only to the capture, not the image itself. When the scanning of your entire library of slides has been completed we begin the second phase. We use a computer application to individually view each slide and make decisions on how the machine information is to be used in arriving at a final, extremely high quality, image.
But what goes into the making of an extremely high quality image? A slightly technical discussion below highlights the major considerations.
DYNAMIC RANGE:
1940 vintage Kodachrome film was incredible with its dynamic range. That is, the ability to capture both dimly lit and brightly lit objects within the same image. For example, suppose the scene was an ocean beach on a bright sunny day. The sands of the beach would be very brightly lit, so much so that were you there you probably would enjoy wearing sun glasses. But let us suppose that within that same scene there were bushes and trees on the periphery of the beach. Let us also suppose that people were within the shade of those trees enjoying respite from the intense sunlight. With insufficient dynamic range the photographer would have to choose what to optimize the film exposure for: the people in the shade or the people on the beach. However, with a wide dynamic range both can be captured. Kodachrome to the rescue: Kodachrome film had a very wide dynamic range, much more than today’s digital imaging is capable of. To compensate, and increase the dynamic range, a second scan is made at a different intensity. The two images are then combined under computer control with a net effect of increased dynamic range. The images in the shade appear more vividly while the images in the bright sunlight retain their full beauty.
DUST AND DEBRIS REDUCTION:
While we go to great lengths to brush off dust and debris from each slide, it is impossible to remove it all. There will always be microscopic dust and debris on any given slide. So, what is a person to do? What we do is make a second scan using infrared technology creating a map of any microscopic dust and debris. This enables computer controlled correction with a net effect of radically reducing them. But what does this mean in consumer perceived terms? Without an infrared scan most slides would still look fine except that under careful examination you would see little annoying speckles. But with the infrared correction the image quality is noticeably improved.
ADAPTIVE CONTRAST TO IMPROVE DIMLY LET AREAS:
Dynamic range has already been discussed above but in many cases there are ranges of light that even Kodachrome could not reach. Adaptive contrast helps to bring out the detail in dark imaging. But too much makes the image look milky. Computer control of adaptive contrast is not viable without an actual human eye judgment. Because the scanner machine information was saved we are able to make those decisions in phase two, that is, AFTER the scanning is done. In software we simply select the level of adaptive contrast that looks the best.
COLOR CORRECTION:
Color correction is especially important when the slides were originally shot using Ektachrome film because Ektachrome dyes fade unevenly with time with the net effect of creating a reddish hue. Computer controlled correction in these cases is very good without human interaction. However, there are other cases where a human eye is needed to adjust any one or all of three imaging “levels.”
Leave a Reply