Fiber Optic or Electrical... which is best?
| Created |
2007-01-26 |
| Modified |
2007-02-06 |
| Views |
5851 |
| Author |
Richard Perry
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Many strobes today come with dual connectivity options, that is they can be fired via fiber optic cable, or via an electrical sync cord. These strobes offer the best of both worlds because they will work with the transparent compact housing that you own today, and they will move up with you should you migrate to a SLR housing in the future. (Never say never.)
For most camera/housing combinations, the there is no choice. Your housing will work with only one type of connection. Some housings however will work with either sync option, leaving the owner to question, 'Which is best?' Both options have strengths and weaknesses, so let's take a look.
Fiber Optic Connections
First, a little background to help understand how these strobes work. Strobes, including camera flashes do not vary in power or intensity to control exposure. The only variable is in the duration of the flash. It's also important to remember that the entire flash process occurs in microseconds.
In flash mode, most modern cameras fire a 'pre-flash', a small short duration flash used to determine the proper white balance for the scene, and how much light is required for the exposure. Based on what the camera 'sees' in the pre-flash, it calculates the duration of flash to apply to the exposure.
Strobes fired via fiber optic cables generally follow a simple concept, they accurately reproduce the camera flash. Fiber optic cables transmit light from the camera flash to the external strobe. The external strobe simply watches for the camera flash to fire, and follows suit. It then watches for the camera flash to quench, and again follows suit. Remember that light travels at 186,000 miles/sec., so all of this watching, firing and quenching happens very, very quickly.
Most modern strobes reproduce both the pre-flash and the main exposure flash, so in effect your camera is controlling the external strobe without every actually knowing about the existence of it.
This pre-flash mimic has another benefit for the camera and housing. The camera 'sees' the bright light from the pre-flash of the external strobe, and calculates (correctly) that less camera flash is required to properly illuminate the scene. The shortened camera flash means less drain on the camera battery, and less internal heat buildup (which can lead to condensation and fogging) within the housing.
Advantages:
- Reliable
- Inexpensive
- Light weight
- No penetration of the housing is required
- Not affected by water
- Easily repaired if damaged - The most common damage to a fiber optic cable is a kink. In this instance the kinked portion can be simply cut off and the remaining end pressed into service again.
Disadvantages:
- Only works with a housing that allows the camera flash to be visible outside of the housing. If the housing is not transparent, or if the camera has a pop-up flash which cannot be deployed in the housing, then a fiber optic connection will not work.
Electrical Sync Connections
An electrical sync connection is just what the name implies. A multi-strand (3-6) wire cable connecting the housing and the external strobe. The camera is aware of and in direct communication with and control of the external strobe.
Advantages:
- Reliable
- Rugged
- Precise strobe control, not limited by the camera flash
- Works with non-transparent housings and housings where the camera flash cannot be deployed
- Some cables incorporate TTL translation circuitry which negates the need to install such circuitry inside the housing.
Disadvantages:
- Generally more expensive
- Requires a camera with a hotshoe
- Requires a breach of the camera housing known as a bulkhead, which is a potential source of leakage
- Can be disabled by moisture in the connectors
So, there you have it. There is no perfect solution, but thankfully there are affordable, viable solutions for almost every camera and housing combination. If you are lucky enough to have a housing that offers you a choice, consider yourself doubly blessed. You can use the electrical option, and carry a light weight fiber cable as a backup!
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