In this digital age, we naturally think that everything about digital photography surpasses the standby of ages past—Kodachrome. You are in for a surprise. The dynamic range of Kodachrome film decidedly outclasses digital scanning technology. But there are other considerations with regard to digital imaging.
WHAT IS DYNAMIC RANGE
But first, what is dynamic range? This is the range an image is able to produce of low to bright segments. A photograph at a sunny sandy beach may have shadowy areas in it. The higher the dynamic range, the more detail will be visible in the shadowy areas.
THE SCANNING EQUIPMENT ITSELF
Image scanners come in different quality sizes and are rated by the specifications of Dmax and Dmin. Therefore, a top-rated scanner will do better in delivering increased dynamic range relative to other models. But even the very best and most expensive scanners and digital cameras cannot compare with vintage 1940s Kodachrome film. But there are tricks that imaging specialists pull to at least gain some ground on Kodachrome film.
WHAT IS THE TRICK
The biggest trick digital specialists have to pull out of their hat is a double exposure. A digital camera will take two photos of the same scene but in a fast enough succession that it might as well be one frame. But one of the exposures will be at a lighter density than the other. The camera then blends them together into one frame with the result that the shadowy regions are lighter.
But you might be wondering about what happens to the brighter regions. These are relatively unaffected since the brighter areas have a high natural transparency.
EXAMPLES
In the example, note that there are shadowy areas in the lower center of the historical plaque which are shown better in the HDR version. In this example, part of the sign base is slightly hidden by the shadow the rest of the sign casts. The second scan at the higher exposure rate brings out this detail at the expense of the nicely exposed region. But when we say “at the expense of,” this is not to mean that the other areas suffer in practice. As can be seen in the example, there is little effect on the properly exposed area. This is because the “super exposed” region’s now over exposed regions have a more transparent effect and therefore are not so much affected. This improvement is not a radical improvement but the increased dynamic range is obvious even to the untrained eye.
Another example is provided of an area of the photo which was not in need of additional dynamic range. That is the area of the historical sign itself. While in this case the adjudication is subjective, at least in this writer’s opinion, the HDR version is an improvement.
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