The Varieties of Flash

“Now that car doesn’t belong.”

Although I had only known Bennie for a short time, it was obvious that he was in possession of an opinionated nature.

It was a clear sky through which the sun ever so richly washed upon us on that late afternoon in May. Chuck had locked the front door of his shop, in which resided a massive collection of used and rare books for the curious and academic. It was upon this exit we found Bennie sitting upon the entrance to his shop of second hand miscellanea.

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Bennie had secured his shop with such enthusiasm as to have even locked away the key; inside the shop no less. Although the thought of leaving Bennie by himself momentarily entertained us, we decided to join him in his wait for the locksmith.

The shops which line that section of North Lime enjoy the company of an upscale steakhouse. As it was late afternoon, the attendance of the steakhouse had already filled the available parking on the street. This had not escaped Bennie’s attention as he began to make his notice of the individual vehicles known.

Bennie had pointed out the Cadillacs, Lincolns, a Mercedes, among the cars that were present. His attention then focused upon one car as he stated, “ Now that car doesn’t belong.”, as he pointed at a 67 Chevy II station wagon, which had seen better days. He rather wondered about Chuck and myself finding humor in his statement as I responded to his quip, “That’s my car Bennie.”

I had previously purchased an old Anscoflex 620 camera from Bennie. It was in great shape, despite its limitations as a camera. I frequently referred to it as the ‘garage door’ camera, as the front lens cover of this simple TLR was silver in appearance and resembled a garage door that you slid up to form the focusing hood. It had also come with a flash unit which used two ‘C’ batteries and used bulbs.

As I was not pleased with the expense of flashbulbs for this camera, and the experimenter in me had to play as well, I had devised a way to use an electronic flash on this camera. I had a folding flash bracket to which I had attached a Vivitar 1900 flash unit. In order to trigger the flash, I had removed the PC connecter from the flash cord, and attached the two wires to the contacts, to which the original flash unit would normally be attached. I was pleased as I tripped the shutter and the flash fired.

This was many years ago and I did not know of the difference in synching electronic and bulb flash. As such, my conversion may have looked neat to me, at the time, but it would not have worked.

I will cover the reason why this is so, and also introduce the varieties of flash and terms you may encounter.

M and X Sync

“There’s something wrong with my camera.”

I have heard this statement from a photographer after viewing a set of dark prints. They had used an electronic flash for their shots, but, alas, all the shots appeared as though no flash had been used. The problem was that they had an older manual focus camera with an M and X sync switch, and they had the switch set to M.

M sync is used for bulb flash, while X sync is used for electronic flash. While electronic flash is instantaneous and fires when the shutter is fully open, bulb flash actually requires a delay to reach peak intensity or else the result will be underexposed. Hence, M sync, and older bulb flash cameras, actually triggers the flash before the shutter opens, so that when the shutter is fully open, the flash is at peak intensity.

If an electronic flash is used on M sync, or an older bulb flash camera, the flash actually fires before the shutter is opened, thus giving no flash illumination. If a bulb flash is used on X sync, the result will be underexposed.

Focal Plane Shutters

“Half the dang picture is black.”

A good number of us have made this mistake. We get the pictures back from the photofinisher, or after developing them ourselves, and part of the picture is properly exposed while the other part is mostly or completely dark, as though no flash had been used. The problem is in the operation that is inherent to a focal plane shutter which is common to SLRs.

A focal plane shutter consists of two curtains which provide the opening through which the film is exposed. Upon tripping the shutter, the first curtain traverses the film plane until it completely clears the frame, then triggers the flash while the frame is completely exposed. The second curtain then traverses the film plane thus closing the opening. This works fine up to a certain shutter speed which is called the flash sync speed, the maximum speed at which the focal plane can remain fully open.

Beyond this speed the focal plane has to operate in a different manner. The second curtain begins to traverse the film plane before the first curtain has completed its movement, thus forming a smaller opening which travels the film plane in a sequential manner. As the shutter speed gets faster, the opening becomes smaller. If a flash is triggered above the sync speed, only part of the film is exposed to the flash, the portion where the opening was in the focal plane when the flash fired.

Your camera manual will provide your camera’s maximum flash sync speed. If you do not have a manual for your camera, most cameras have the flash sync speed highlighted in a different color on your shutter speed dial. If you have no such designation, then you can use a rule of thumb based on the focal plane shutter itself. If the curtains of the shutter travel in a horizontal plane, you have a maximum sync speed of 1/60 of a second. If the curtains travel in a vertical plane then you have one of three maximum sync speeds. If your speed dial has a setting for 1/90, that is your max; if it has a dial setting for 1/100, that is your max. If the speed dial has neither speed, then your max is 1/125. This is a rule of thumb and not an exact science.

There are some cameras, when used with a dedicated flash, which can provide flash sync with the first curtain or the second curtain. This feature is called Second Curtain Sync. Its primary function is for the use of a slow shutter speed with flash when used with a moving subject. Since the flash freezes the subject, but the slow shutter speed records an additional blurred image of the subject, this can give the appearance of movement in a photo. With first curtain sync, the blur of movement has a tendency to appear ahead of the subject. Second curtain sync allows the blur to appear behind the subject, in most cases.

Types of Portable Flash

“Put a head on that.”

Portable flash units come in two configurations; the hotshoe mount flash; and the handle mount flash, often referred to as a ‘hammerhead’ or ‘potato masher’ flash. There are variations on these themes as different units have bounce heads, allowing the head to be positioned straight up, forward, or somewhere in between; swivel heads, which allow the flash head to be moved left or right; zoom heads, which allow the angle of light output to be narrowed for use with a longer lens and can provide a greater working distance to compliment the longer lens; portable power pack, allowing longer use on battery power and often faster recycling of the flash; and bare bulb units, which come with a removable reflector allowing the light to be directed or used bare bulb allowing a wide coverage area. The handle mount flashes offer more power than their shoe mount counterparts.

Of note is that most flash heads use a lens which provides light coverage for a 35mm lens (55-60mm for medium format 645) which provides coverage for lenses 35mm or longer. If using a wider lens, there can be light falloff toward the edges and especially the corners of the frame. To prevent this, most flash units come with a wide angle diffuser which can be attached to the front of the flash. Barring this, other diffusers and bounce cards, which will be discussed later, can be used to provide a wider angle of coverage.

Manual Flash

“I didn’t know it had a first name.”

A manual flash unit, or an automatic flash in manual mode, offers the ability to maintain a set output. The flash is rated by a guide number which provides the basis for calculating your exposure. The guide number is divided by the distance in feet to give you the aperture at which you need to set your lens. If you have a flash with a guide number of 120 and are shooting at a distance of 15 feet, your aperture should be set at an F8. Conversely, if you were shooting at a distance of 10 feet, your aperture should be set at an F11. When in doubt, round down to the next closest full or half stop.

This guide number is based on ISO 100 film. If you are using 200 speed film, add half the guide number to itself. If you are using 400 speed film, double the guide number. This is a rough estimate which is easier to use than calculating exactly. Since all flash units usually include a scale, calculations are usually unnecessary.

On European equipment, the guide number is rated in meters rather than feet. You can either divide the guide number by meters or convert it to feet by multiplying it by a value of 3 1/3, or 3.28 if you want to be specific.

For those who may be using an ISO 160 film, rather than trying to calculate the guide number, just treat it as a 100 speed film. This will give a little overexposure which will give a slightly softer contrast. Conversely, for those who are interested, a slight underexposure will give a slight increase in contrast. And, of course, a lot of underexposure will give you a dark picture (I couldn’t resist).

Automatic Flash

“I like a flash that does it all for me.”

Well… not exactly. Automatic flash offers the ability to free up your decision making. An automatic flash unit has auto exposure modes which are controlled by a light sensor. These modes are represented on your flash unit by range and aperture. Like the guide number, your f-stop is higher at shorter ranges than at longer ranges. This, however, does give you the ability to set your flash and aperture to compliment each other so that any shot you take within the specified range will be properly exposed.

The automatic flash works by using a sensor to measure the amount of light reflected back to the flash unit. When the value of the light equals the desired output, the flash is automatically squelched, thus giving a proper exposure. Although this would seem failsafe, it is not as the sensor can be fooled just as a meter can. In a scene with a lot of white, the flash will most likely underexpose the shot because of the amount of light being reflected by the white causes the flash to shut down prematurely. You can counter this by opening your aperture by one stop while leaving the flash at its current setting. Conversely, a scene with a lot of very dark colors can cause the flash to overexpose the shot. You then need to close the aperture by one stop to counter this.

Continue on to The Varieties of Flash: Part II