This First Part is mostly Historical in Content
Freezing Splashing Milk in a Bowl
I have quite a library of vintage photographic books. Some were my dad's and some I acquired as an avid reader from the time of was able to read forward. I can't readily name the book, but I recall the page very clearly. Everything was black and white, but there was a picture of a close-up view of milk splashing into a bowl. The image was frozen just after a drop had impacted and caused a splash. It was fascinating to me. This is the kind of thing you can't really see with the naked eye. Our eyes and brains are designed to see the continuum of the whole process. They do not see "fast enough" to dissect the process into these minute slices of movement. Maybe people could even be trained to see this way.
I have a great old lens from a training device used to train troops to quickly identify both enemy and friendly aircraft during WWII. It uses a shutter to project an image at shorter and shorter intervals. It works. It has been said, although I don't recall by by whom, that the Evelyn Woods Speed Reading Courses that many we baby-boomers were exposed to during our childhoods was inspired by the success of this device. But I don't think we could ever learn to see the frozen image of milk splashing that I recall from that old photography book.
When I first saw the splashing milk image, I was still constrained to the use of flashbulbs for photographic image illumination--those or constant flood-light illumination. Flashbulbs were/are relatively slow compared to today's modern electronic flash units that are taken so much for granted today. Some of the bulbs illuminated even slower than many camera shutter-speeds. For this reason it was necessary to make sure your bulbs matched your shutter speeds so that the shutter did not close before the flashbulb had reached its peak illumination. This was called synchronization.
Anyone who ever used an old film camera without an "X" synchronization feature while using an electronic flash, can tell you of the disappointment of finding blank or only partially exposed-frames when they developed their film. In those instances, the electronic flash had actually fired in entirety before the mechanical shutter could even open. So the images were actually never exposed at all--or if they were, it was with only the much weaker available-light illumination and were blurred or very faint ghost images.
Newer cameras have an option of one or more bulb settings as well as the necessary crucial electronic flash settings; still newer cameras are simply wired for electronic flash only. They won't even work with bulbs. Such is the nature of technology. So it was in the early days that Ifound such fascination in the high-speed photograph taken up close of the milk drop splashing. But I had to wait to be able to duplicate this speed-light effect. I had to wait until electronic flash units became available to average consumers--and were affordable.
Even then, the first professional consumer models of electronic flash units that were such a boon to news, sports, and wedding photographers yielded relatively slow-speed flash output. It was not until the advent of electonic speed-lights that offered an automatic-exposure feature--that truly high-speed photographs capable of stopping such rapid motion as the milk splash could be done by the average professional photographer.
Although these automatic electronic speed-lights were very expensive, they were one of the most significant advances in photographic capabilities of the century. Prior to this time, photographs taken with the aid of manual-exposure electronic speed-lights had to be calculated with a formula to allow for the distance. If your distance-estimating was not accurate, your image was either over or under exposed--by a lot. although I won't here go into the use of guide numbers to aid in these calculations, but I will tell you that it is a tribute to the remarkable abilities of ones brain to adapt to make these calculations on the fly--without really thinking much about it. But it did take experience. It was one of those skills that set a true craftsman or good news photographerher from those without such skills. And there were still benefits to having this skill long after the arrival ofautomatic speed-lights.
An unintended feature that came about as a result of how these new automatic-exposure speed-lights were able able to achieve their automatics. It was really a very simple, though ingenious concept. An electronic photosensitive sensor was installed facing outward on the front bottom of the speed-light's face. These were often referred to as an "electronic eye". The sensor was designed to pick up the reflection of the flash illumination from the subject; the farther away the subject was, the longer it took for the reflection to return to the sensor. The flash would "stay on" until the sensor shut if off.
Light travels at 186,000 miles per second--which is, for most practical purposes, instantaneous. But when measured by the sensor and the automatic switching circuits of the electronic flash, the difference is enough to make a difference in the amount of light that is allowed to reach the subject. So the closer the flash source is to the subject, the shorter the time it stays on, thus decreasing the amount of light "dumped" onto the subject by the time it shuts off. Conversely, the farther the flash is from the subject, the more light is allowed to reach the subject.
Although it was the long way around to get to this point of my speed-light explanation, this brings us to the unintended, or side benefit of the electronic flash. The operation of the electronic flash at close distances, caused the flash to shut off very quickly while still providing sufficient light for proper subject illumination. This placed truly high-speed exposure capabilities into the hands of anyone willing to spend the moderate amount required to own an electronic flash.
The speeds at close ranges were 50,000th of a second or higher. This is pretty quick by any standards. But it was very quick back in the day. The next post will tell you how to use the electronics of any inexpensive medium-grade consumer compact digital camera to do high-speed photography.