Strobe: technically, stroboscopic light is a repeating light, such as an automotive timing light or a disco strobe. In general usage, the phrase is used interchangeably with electronic flash.
PC Cord: A connecting cord for the flash. Named for the Prontor-Compur shutterworks in Germany which developed the shape of the tip.
Hot shoe: a flash mounting slot that has a central terminal so no cord is needed.
Synchronization: the timing of a flashgun and a camera so that the flash is making the most light while the shutter is open.
M Sync: a delay of .026 seconds between the flash starting to fire and the shutter opening. This allows old flash bulbs to reach their peak output.
X Sync: a xero (zero) delay. When the shutter is fully open, the flash is triggered. This is what is needed for electronic flash. Most cameras with focal plane shutters, such as SLRs, have X sync at speeds up to 1/60th of a second. If you take a flash picture with the shutter speed set higher than the X sync speed, you get a picture that is partially blacked out. Some premium cameras offer the feature of a high shutter speed for X sync. This minimizes the chance of a "ghost exposure," one which is made not by the flash but by the existing light.
Automatic Flash: an electronic flash that measures the amount of light which has gone to the subject and bounced back to the flash. It turns the flash off when enough light has been returned for a proper exposure. It can do this in as short a period of time as 1/50,000th of a second.
With an automatic flash, the photographer sets the lens opening once, according to a calulator built into the flash gun. For example, the flash may show that with ISO 200 film, the lens should be set to f8. At all distances up to the maximum range of the flash, the flash will measure light returning from the subject and turn itself off when just enough light has been returned for a proper exposure at f8. The concept is similar to that of a toilet mechanism, which fills itself to a present level and then stops the flow.Early and lower-cost automatic flash guns used a simple switching mechanism. Initially power from the capacitor goes to the flash tube. When the "brain" of the flash decides there's been enough light generated, the remaining power from the capacitor is diverted to a dump tube, which wastes it.
- Fresh batteries (or rechargeables)
- Close distance
- Large lens opening
- Old 35mm rangefinder cameras with cloth shutter curtains (Leica screw mount, Exacta, etc) 1/25th or 1/30th second
- More modern 35mm with cloth or horizontal metal curtains (Leica M-series, Canon VI, Nikon F, Pentax Spotmatic, Minolta SRT-series) 1/50th or 1/60th
- 35mm SLR with metal shutter which moves vertically (Nikkormat, Konica T series, etc) : 1/125th second
- Leaf shutter cameras (the shutter is in the middle of the lens) such as Rolleiflex TLR, Kodak Retina: any speed up to 1/500th
Thyristor: a special type of switching mechanism on an automatic flash which saves the energy not required during a short flash. It simply stops the flow of power from the capacitor to the flash tube, instead of wasting it by "dumping" it. This means that a thyristorized flash gun will recycle more quickly and give more flashes on a set of batteries before they run down.
Recycle Time: how long you must wait after one flash before the flash is ready again. With a thyristorized flash the following choices make the flash recycle faster:
A TTL flash system uses a sensor in the camera to measure the flash Thru The Lens, which is more accurate when taking extreme closeups or using a long lens.
Dedicated flashguns are designed to work with a specific late model camera or family of cameras. They have additional connectors to carry information back and forth between the camera's brain (CPU or Central Processing Unit) and the flash. All dedicated flashguns set the camera to the one and only proper shutter speed for flash sync. Some also set the lens opening, on cameras which have automatic lens opening exposure systems. Most activate a flash readilight in the camera's viewfinder. Older cameras with mechanically timed shutters don't need, and can't take advantage of a dedicated flash.
Multi-dedicated flashguns by companies such asVivitar, Sunpak, Rokunar, Achiever, etc, can be adjusted to provide minimal dedication with several different brand cameras. In general, they will set the proper shutter speed, activate the readilight in the viewfinder, but will not set the lens opening.
Some flashguns, such as the Minolta 280PX, do not have a built-in exposure sensor. They can only be used on specific cameras that have a built-in sensor for TTL flash. For example, the Minolta 280PX can only be used on the X-570 and X-700 cameras.
Autofocus cameras usually have full dedication and also a built-in near-infrared light source that makes it easier for the camera to focus in low light levels. Failure to use a fully-dedicated flash wipes out many of the benefits of buying such a good camera.
What shutter speed can I use?
If the light from a flash picture is to get to all of the film, then all the negative area must be uncovered when the flash goes off. With a focal plane shutter, at high shutter speeds only a portion of the negative is uncovered at any instant - a slit exposes each segment sequentially. That's the reason you'll sometimes see a photo properly exposed at one end and very dark at the other.
Some top-end cameras can be used with special flashguns at really high shutter speeds such as 1/4000th of a second. The special flash actually lasts long enough for the shutter curtain to complete its passage across the full length of the film.
Most cameras require that you use a slower shutter speed. On some, the highest shutter speed that is usuable with electronic flash will be painted a different color on the shutter speed dial, or marked with an "X."
Here's a rough guide to camera types and the highest shutter speed for flash sync (a slower speed is always safer)
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