How to choose a suitable strobe for your camera system.
The following is a simplified outline to help you get started in selecting the strobe flash you need for underwater photography.
When you select a digital camera and underwater housing, you must consider the limitations of the underwater photographic world where there is little ambient light (available light) and color (water removes the red color spectrum), except for blue light. Also, the water is dense and particles that are suspended in the water column and improper placement of the camera’s strobe causes the light to reflect on the floating particles thereby generating “back scatter” and show up as white specks in your image, making it look like you took images in a snow storm.
An external strobe helps to reduce these effects if properly aimed, but both the camera and strobe must meet some conditions for good results. Using the camera’s own flash puts it too close to the lens and back scatter from the particles will result.
If you chose wisely, the strobe flash, the arm and connectors will be able to be used with almost any camera system. If you decide to change cameras and housings it is a very good possibility that your flash system will be able to be used with it, thereby saving you a lot of money. The rule here is, when you buy a flash system look ahead. You may have to spend a little more now but the savings the next time around can be well worth it.
Most digital cameras use a special flash (or even multiple pops) to determine correct exposure and color settings and adjust the auto focus of the lens. This so-called “pre-flash” is generated before the actual flash and exposure are made.
Most conventional slave strobes are not able to correct for the pre-flash and will be triggered by the pre-flash. They cannot recycle quick enough to fire again on the actual flash exposure which is about 200 milliseconds later. A special circuit is needed to ignore the pre-flash.
The newer digital strobes can ignore the pre-flash. Some models can even generate their own pre-flash for the camera to read when there is no on-board camera flash. Many DSLR flash units can do this as well as the smaller point and shoot flash units.
Digital flash types
The two types of flashes are used with digital cameras are:
Full-Flash: A camera that uses full-flash will always fire it’s strobe at full strength and the camera will adjust the CCD’s sensitivity to create the right exposure. The camera controls the exposure.
Metered-flash: Metered-flash cameras will stop the internal strobe once the right exposure has been obtained by”quenching”or cutting the flash power. The strobe out-put is controlled for the exposure.
TTL (through-the-lens) is a Metered flash in which the camera and strobe communicate to obtain the right exposure. The camera evaluates the light reflected from the subject and informs the external strobe about the required strength and duration need to get a proper exposure. TTL simplifies underwater flash photography, but it doesn’t work accurately and leaves a need for manual adjustments on the strobe. TTL exposures work well about 50% of the time and will give an acceptable exposure.
In order to use TTL functionality, both the camera and strobe must be directly connected with a cable called Sync cords. The housings will need special electrical connections to the camera called bulk-heads. What is new is fiber optical cables have been introduced and in some strobes they can work in the TTL mode and will read the camera’s flash.
TTL, E-TTL, i-TTL, etc.
Digital SLRs do not use the the older Nikonos TTL protocol left over from the 1980′s, but use their own proprietary version like E-TTL for Canon cameras and D-TTL and i-TTL for Nikon. These cameras can generate multiple pre-flashes as well as a pre-flash with an delayed duration. The older Standard TTL strobes are therefore not capable of working with these newer cameras and require additional special circuits. In order to work in the TTL mode, conversion circuits are required. The Sea&Sea YS strobe line has built-in Canon E-TTL support and Ikelite has a good working circuit for their DS-51 and DS-160 flash systems to support digital TTL requirements for both Nikon and Canon cameras. Inon has both fiber optic and direct connect for some of their models and can support most TTL requirements.
Besides the special underwater strobes, many manufacturers also provide housings that allow underwater use of popular surface flashes, such as the Nikon SB-800/400, Canon Speedlite 580EX and Olympus FL-20. Using a dedicated manufacturers strobe will give you both a strobe to use above water and well with your underwater housing.
When combined with a suitable camera (usually a digital SLR), camera housing and sync cord, all restrictions on digital protocols are matched and full TTL compatibility is achieved.
In Slave Mode, a strobe will detect the camera’s flash out-put with a light sensor. As the camera’s internal strobe fires, the light will trigger the external sensor and cause the external strobe to fire too.
A disadvantage of this method is that the camera is not “aware” of the presence of the external strobe and you will be using more of the camera’s battery power, shortening the life of the battery. The camera will not be able to adjust for a large amount of light out-put by the strobe. To prevent overexposure, the camera must be prepared for the additional light manually. The strength of the external strobe must in many cases also be decreased so it is necessary for the external flash to have power settings so you can reduce the out-put of light.
Ikelite has their DS35 strobe to work with metered-flash cameras and stop at the moment the internal strobe stops. This will further decrease the amount of light and improve exposure.
Some strobes, like the Sea&Sea YS-110a and the Inon D-2000 offer a special buit-in slave mode to automatically adjust the power output to the conditions. This method is based on setting the camera’s aperture on the strobe, and the strobe matching its output by measuring the ambient light with its own meter.
This mode may not always be usable given the fact that not all compact cameras show the aperture to the user. The position of the strobe to the camera and subject may cause it to measure an area with different brightness The camera will see something different and not produce the proper exposure.
Strobes such as the Sea&Sea YS-110a TTL and the Inon D-2000 offer these optical slave-TTL types. With S-TTL (Optical Syncro TTL) and DS-TTL (Digital Slave TTL) the external strobe not only watches the start of the camera’s internal flash, but also when it stops. When the camera has determined the proper amount of light for correct exposure has been received, it will cut off its flash out-put.
Open Connections (slaved)
No direct connection (as with TTL) is required for these types of strobes; an underwater camera housing that permits the use of the camera’s flash is sufficient. However, this also increases the chance of misfiring. Where there are no objects in range to reflect the light of the camera’s internal strobe, the external strobe’s sensor might not receive enough light to trigger it. This is where the introduction of Fiber Optical sync cables have come into use. They direct the camera’s flash directly to the strobe’s sensor. They also help prevent some one else’s flash from firing yours.
Slave strobes are used with Point and Shoot cameras that do not have hot shoe connections or SLR that have pop-up flash units. Many new SLR housings can take advantage of this as they are fitted with Optical sync ports.
1. Check if the strobe and camera can work together and that TTL-mode requires both a compatible housing and camera and connections, otherwise your choice is limited to slave strobes. Some strobe model can provide both slave or connected sync.
2. A good slave strobe will verify the camera’s flash so check to see if it can be used with the housing and that the pre-flash can be disabled or that the strobe can synchronize with the pre-flash.
3. Choose a model with a power matching your needs: a higher guide number is useful for wide angle photography or when shooting macro with very small apertures. But it may also increase the backscatter by reflection on dust particles. A variable power setting gives you more flexibility and many of the smaller point and shoot cameras do not stop down more than f8.0 and powerful strobes are useless for these cameras.
4. The angle of the flash coverage should match the camera’s widest lens setting. Diffusers may help to spread the strobe’s beam angle and reduce the power out-put.
5. A fast recycle time is important if you want to shoot series of photos in quick succession. DSLR’s can shoot up to 8 frames per second without the camera showing down to write to the storage card, here a fast recycle time is good. The smaller cameras can take up to 4 seconds before the next image can be taken and does not pose as much of a problem although some strobe at full power can take as much as 8-10 seconds to recharge. A long recycle time may cause you to miss the shot you really needed.
6. The number of flashes you get from a strobe depends on the quality of the battery you are using and power settings you are using. Temperature will affect the battery life.
7. Attaching the flash to your housing will require additional hardware such as a camera tray and flash arm with all the proper connections.
Here are the strobes we have used and tested that we can recommend. There are other strobe units but this selection has proven to be the most versatile and reliable.
SMALL STROBES FOR POINT AND SHOOT
|Sea & Sea YS-01||Sea & Sea YS-02||Sea & Sea YS17||Fantasea Remora||Inon s2000|
|Inon D-2000||Ikelite DS51||Ikelite AF35||Sea & Sea YS-D1|
STROBES FOR DIGITAL SLR HOUSED CAMERAS
|IKELITE DS161 WITH VIDEO||IKELITE D200||Sea & Sea YS-110a||Sea & Sea YS-250 Pro||Inon Z-240|
HOUSED MANUFACTURERS STROBE UNITS
|Subal Nikon D80 Flash Case||Nexus Nikon D400 Flash Case||10Bar Canon 220EX Case||
10Bar Canon 580EX
To see which flash unit will work for you. We will make sure you get the right one and one that will fit in your budget.
YS-D1 DS-TTLII STROBE, SS-03114 • Price:$750.00
Estimated availability February 2012. Preorder now to reserve your YS-D1 today.
The YS-D1 is the most advanced strobe SEA&SEA has produced in its 40 year history. Drawing on inspiration from the YS-110, YS-110 Alpha and YS-50Pro, the YS-D1 is robust in features, but compact in size. The YS-D1 includes revolutionary technology such as DS-TTLII with exposure compensation adjustment, an auto-sensing slave switch, built-in high intensity LED target light, and a variable guide number from 32 to 20. It’s 25% more powerful and 10% smaller than the YS-110 Alpha and is compatible with fiber optic cable and 5-pin N-type sync cords. The YS-D1 comes standard with 2 diffusers and 2 strobe mounts and is powered by 4xAA batteries.
Features/Specifications: -25% more powerful and 10% smaller than the YS-110Alpha?-
Variable Guide Number: GN 32 (80×80), GN 24 (100×100), GN 20 (120×120)
All new DS-TTL II with exposure compensation (EV): +/- 4 steps-3 TTL circuitries: DS-TTL II, Slave TTL,
Conventional Nikonos type-Manual GN control: 11 steps -Auto-sensing slave ON/OFF switch (automatic)-3 LED indication lights: l: Ready lamp: red, TTL confirmation: green, Slave TTL mode: blue-Built-in LED target light-Auto power OFF function-Pre-flash cancellation mode-Color temperature: 5600 degrees K (w/o diffuser), 5250 degrees K (w/diffuser)-Standard with two diffusers: Diffuser 120 and Diffuser 100-Standard with two strobe mounts: YS mount, 1″ Ball joint mount-Depth rating: 330ft/100m?-
Compatible cords: 5-pin Sync Cord/N and Fiber-optic Cable (L-type)?-
Power source: AA battery x 4-Recycle time: 1.9 sec. (with Ni-MH batteries)-Depth rating: 330ft/100m
*Specifications subject to change without notice.