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Choosing The Right Strobe Connection - Fiber Optics Vs. Wired Sync Cords
 August 17, 2010 @ 10:37 PM (EST)
Words By Matt Weiss.
Images By Jacalyn Pelloni
There have been a number of new developments in housings recently, one of which is that  fiber optics have become the standard on DSLR housings.  This has caused many DSLR users to debate which strobe connection is right for them, so we have come up with a list of the benifits and issues with each type of connection.

Keep in mind this is  meant for SLR users, but there is a lot useful general information on both hard wired and fiber optic sync cords as well.
A Sea & Sea fiber optic cord

The Short Version

There are two main ways to connect your strobes to your camera: hard-wired sync cords and fiber optic cords. The first, hard-wired sync cords are electronically connected to your camera by connecting the cord to a bulkhead on your housing, which is wired to your camera’s hot shoe. The electronic connection means that you do not need to use your cameras internal flash, which has a slow recycle speed and drains battery life.  However, these cords are very expensive, fragile and require o-rings to create seals, meaning that they have the potential to flood.

The second, fiber optics cords transmit light from your camera’s flash to trigger your strobe.  They connect to the outside of the housing, so there is no potential for leaks and they eliminate the hassle of maintaining extra o-rings.  However, relying on the camera’s internal flash has its flaws, including slow recycle times and draining the camera’s battery.

Pros of Hard-Wired Sync Cords
  • Do not rely on camera’s internal strobe, which are slow to recycle and drain battery power
  • Cons of Hard-Wired Sync Cords
  • Create points for potential floods
  • Require extra maintenance of the cord’s multiple o-rings
  • Are expensive, but also very fragile
Cons of Hard-Wired Sync Cords

  • Create points for potential floods
  • Require extra maintenance of the cord’s multiple o-rings
  • Are expensive

Pros of Fiber Optics

  • Connects to the outside of the strobe and housing, eliminating extra points for potential floods.
  • Requires no o-ring maintenance
  • Cheaper than hard-wired sync cords
  • No additional TTL converter necessary for TTL photography.

Cons of Fiber Optics

  • Relies on internal flash, which is slow to recycle and drains the camera’s battery power
  • They are very fragile

Strobe Connections – What Are They?

Strobe connectivity refers to the way you decide to connect your strobe to your camera.  For SLR users, there are two ways for your camera to talk to your strobe – fiber optics or wired sync cords.  While the method of connectivity will not necessarily affect the outcome of your images, and  the type of connection does not affect the light that comes from the strobe, one method may be better suited for your needs.
Hard Wired Sync Cords

A dual sync cord
Hard-wired sync cords have long been the standard method for SLR users to connect their strobes to their camera underwater.   The wired sync cord connects your strobe to a bulkhead on your housing. The bulkhead is connected to your camera through wires inside your housing that can attach to your camera’s hot shoe.  Obviously, the sync cord must connect to both your housing’s bulkhead and your strobe so make sure you check what type of bulkhead your housing uses.  This is especially important if you are using either an Ikelite strobe or housing because they use their own type of connection, while most of the major manufacturers support the more standard Nikonos 5 pin bulkhead.
Different types of hard wired sync cord connection

Some housings have two bulkheads, while others only have one. If there is only one bulkhead and you want to use two strobes, you will need to get a dual sync cord or Y-sync cord that has one connection to the camera’s bulkhead on one end, and is split on the other end, so it can connect to two strobes.

The wired sync cords have o-rings at each connection point to make watertight seals.  This is one of the main downsides of using hard-wired sync cords -- they can leak and are in fact among the most common types of leaks.  Additionally, you have at least three extra o-rings that require maintenance, which is time consuming.

Hard-wired sync cords are also quite expensive and, unfortunately, very fragile.  They can easily break, and extras are always recommended

The advantages of using hard-wired sync cords are that they don’t rely on the cameras internal flash, which every other method relies on.  A camera’s internal flash takes a lot of time to recycle and drains the cameras batteries, making hard wired sync cords the fastest way to fire strobes and also the most power efficient.

A Sea & Sea hard wired bulkhead

Fiber Optics
Fiber optic connectivity was once only reserved for cameras that didn’t have hot shoes, mainly compact cameras. However, sometime at the end of 2009, housing manufacturers started to realize that this was an oversight, since using fiber optics can have many advantages.

Fiber optic cords allow light from the camera’s internal flash to trigger your strobe. One end of the cord attaches to the outside of the housings, right above where the cameras internal pop-up flash sits, and the other connects to your strobe.  A housing that supports fiber optics will have some sort of “bulkhead” that will allow you to securely attach a fiber optic cable to the housing and allow the light from the cameras internal flash to reach the cord.  When the camera fires, the light from the camera’s flash is transmitted through the fiber optics, which triggers the strobe to fire.
Nauticam housing with fiber optic bulkheads
There are some clear advantages of using fiber optics.  The most obvious is that all connections are external, and therefore they don’t create any potential places for leaks as hard-wired sync cords do.  Also, because all connections are external there is no need for o-rings, making fiber optic cords far easier to handle.

Another benefit is that fiber optic cords are relatively cheap and at around $100 per cord, they are about half the price of hard wired sync cords, and they take up about half as much room in your camera bag.  

Since fiber optics are transmitting light from your camera’s internal strobe, they can utilize optical TTL, also known as S-TTL. If you are using a strobe that supports optical TTL, this is another benefit of using fiber optics.   When using hard-wired sync cords, you will need an additional TTL converter to shoot in TTL (unless you are using Ikelite, which comes with a TTL converter installed).
Nauticam fiber optic cord

However, there are a number of major downsides to fiber optics.   The most serious issue with fiber optics is that it relies on the strobes internal flash, which takes a long time to recycle – up to almost 4 seconds at full discharge on some models.  That means, that while your strobes may be fully recycled and ready to fire, they can’t be triggered because the cameras internal flash is still recycling. This is enough for many photographers to swear off fiber optics completely, as it can be very frustrating to watch a scene unfold only to miss it because you can’t fire your strobes.
Sea & Sea housing with fiber optic bulkheads
Another problem with using the camera’s internal flash is that when the flash is active, your shutter speed is limited to the sync speed of the internal flash, which is usually slower than that of an external strobes.

Lastly, the camera’s internal flash drains the camera’s battery.  While your camera is certainly capable of lasting a dive or two, if you are doing a full day of multiple dives and firing off a lot of shots, you will need to change the battery far more often than if you were using hard-wired sync cords.

It’s also worth mentioning that fiber optic cords are quite fragile. A bend or kink in the cord can prevent the light from traveling through it, which will obviously result in your strobes not firing.  It should also go without saying that if you are using a top of the line, professional full frame camera without an internal flash, you will not be able to use fiber optics without some DIY modifications.

A Nauticam fiber optic cord that connects to a Sea & Sea strobe

So which strobe connectivity is right for you?

Which type of connectivity you use is only a question you can answer.  If you want to eliminate extra points of potential leaks, the hassle of extra o-rings and the cost of  hard-wired cords, consider fiber optics.  If your shooting requires that you fire off multiple frames at a time and can’t wait for the camera’s internal strobe to recycle, stick with hard-wired sync cords.  


marc Weinstock
Oct 14, 2010 12:03 PM
marc Weinstock wrote:
Here is an idea: for sttl, can the camera manufactures include a setting to lower the power of the internal strobe so it will use a less energy to control the external strobe, not the full power to light the subject. I think the problem with this is the internal strobe bulb only has 1 intensity setting and light output is controlled by the length of time it is on.

Another fix would be a LED light of the hot-shoe to control the external strobes which would use much less power.
Jason Heller
Oct 15, 2010 5:37 PM
Jason Heller wrote:
I think there are hotshoe LED lights for that purpose, but have had a hard time finding them to recommend. If you know of some, please let us know thanks!
Samuel Guilarte
Mar 15, 2011 5:45 PM
Samuel Guilarte wrote:
For my Canon T2i (550D) I can set the Flash exposure compensation up or down 2 stops (this affects only the brightness of the built in flash).
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