Underwater Strobes & flashes

Features & comparison of strobes for compact & dSLR underwater cameras

            An external underwater strobe, also known as an underwater flash, is very important in underwater photography. It allows you to reduce backscatter, and enables you to try different lighting options. After a camera housing, it should be your first purchase. Inon, Ikelite and Sea & Sea are popular makers of underwater strobes.

            You can also learn about how to light underwater with strobes, and learn about various underwater strobe positions.

            Underwater strobes come at many different price points, from $75 to $3200. Here's their features, and what you should look for to get the best possible underwater strobe:

Underwater Strobe power:               

• More is better. Power of an underwater flash is usually given by a guide number. The higher the guide number, the stronger the strobe. The precise formula for guide number = distance * F-stop. For example, a strobe with a stated guide number of 20 (meters, above water) might have a guide number of 10 underwater. This means, if you are shooting at a subject 1 meter away at full strobe power, at ISO 100, F10 will give you the correct exposure. At 2 meters away, you will need a larger aperture, F5.6. At a half meter, you would use F20.
• Guide numbers are usually given in meters, at ISO 100, usually above water but sometimes below water. Check to see if this number is with a diffuser or not, since a diffuser will reduce the guide number. when you look at the power of a strobe, you must also look at the angle of coverage. For example, the Ike DS-51 is fairly strong, but has a smaller angle of coverage, so this strobe needs less power.
• Also keep in mind that strobe guide numbers sometime vary from real world results, as you see in this article. View the strobe choices below for more insight on strobe power.

Strobe Angle of coverage

• You will want a higher angle of coverage for wide-angle shots. Strobes like the Ike DS-51, with an angle of coverage less than 90 degrees, are sufficient for macro. Strobes meant for wide angle usually have an angle of coverage of 90-100 degrees or more in both directions. The number quoted can be with or without a diffuser, so check the specifications carefully.

Recycle rate of the underwater flash

• Faster is better. 1 second is considered very good, 3 seconds a little slow. This recycle time is only for a "full dump", which means the strobe fires for its maximum duration. Lower strobe powers will recycle faster. Remember, when comparing strobe recycle rates, you also have to compare them at the same power setting. If Strobe A and B have the same recycle time, but Strobe B is a stronger strobe than strobe A, Strobe B will recycle faster than strobe A when both are set to Strobe A's maximum power. 

Shots per full battery charge

• More is better; the normal range is 100-300 shots per battery charge, assuming a full dump (strobe is fired at maximum power). The best batteries for your strobe are usually 2700mAH or 2900mAH rechargables. Batteries often don't meet their specs, so get a high-quality battery like Maha powerex or Sanyo, and check out battery reviews. 

Underwater strobe Size and weight

• Less is better. Figures are usually given for above water, and under water.

Spotting light

• A spotting light, also know as an aiming light or a modeling light, is a light that comes out of the strobe, lighting up the subject to help with auto-focus. I find very few people use this feature, most of the times strobes are not aimed exactly at the subject. They are very useful as a backup light on night dives though, or as an emergency focus light if your focus light goes out or floods. They can also be used to help you know which exact direction your strobe is pointing.

TTL converter compatibility

• Not all strobes are compatible with each TTL converter available.

Color temp of a flash

• Color temp of most strobes will range from 4700 to 5600K. See the color temperature section for more info. A slightly lower (warmer) color temp, e.g. 4700K, can be beneficial for WA shots, because of the better blues it produces. Some of the highest end strobes, like SeaCam, even have adjustable color temp.

Bulb size

• some more expensive strobes have a tubular or curved bulb for better quality of light. The difference will be very subtle.

Recommended underwater strobes:

dSLR users:

Some of the popular underwater strobes or flashes for dSLR users are the following: S&S ys-90, S&S ys-110, IKE ds-125, INON Z220, INON z240. All are excellent choices, at different price points. Subtronics and SeaCam have a good reputation at a higher price point and are used by many professionals. Ikelite just came out with a stronger DS-160 strobe, which is also popular. S&S just came out with the YS-110a for serious amateurs, and the YS-250 for professionals. Some people may start choosing the Inon S2000 for a small macro setup - read my Inon S2000 review.

Compact camera users:

Inon S2000 (just released), Inon D2000, Sea & Sea Ys-27, Sea & Sea YS-110, and Ikelite DS-51s are all popular. There's also an article that covers several types of less expensve strobes for compact cameras here.

Underwater Strobe Chart

Special thanks to Bill Van Antwerp for helping me put together this underwater strobe chart.

Strobe choices - a quick overview

I'm going to give a quick overview of some of the most popular mid-level strobes. This does not cover some of the very inexpensive strobe makers like Fantasea or Epoque, or the more high-end strobes like SeaCam, Subtronic or Hartenberger.

Strobes are listed in order of increasing power.

Sea & Sea Strobes

Good quality strobes, often paired with a S&S camera or a S&S TTL converter.

• YS-17TTL - not considered a good strobe for the money
• YS-27dx - Popular choice for compact cameras with fiber optic cable
• YS-01 - New strobe, direct competitor to the Inon S2000, very similar specs.
• YS-02 - same as YS-01, but less expensive - no TTL or LED modeling light.
• YS-90 - Replaced by the YS-110
• Sea & Sea YS-110 - Replaced by the YS-110a, good choice for macro & wide angle. Three second refresh rate at a full dump. Read my YS-110 review, and the comparison of the YS-110 and the Inon Z240.
• Sea & Sea YS-110a - Faster refresh rate than the YS-110, 1.5 seconds on a full dump. Good choice for macro & wide angle. Has an optical TTL feature. The YS-90, Ys-110, Ys-110a are slighly weaker than the DS-125 or Inon Z240. They are used by compact and dSLR users. 
• YS-250 - Professional level, very strong, larger & heavier, made for wide-angle.

Ikelite Strobes

Excellent reputation for strobes, known for good color temp (Ikelite DS-125 & above) and fast refresh rate. Strobes are larger & heavier than S&S and Inon, and take a proprierary battery pack. People with Ikelite housings usually get Ikelite strobes so they can use the Ikelite TTL converter. A separate manual controller is needed to work with a fiber optic cable.

• Ikelite DS-50 - Replaced by the DS-51
• DS-51 - Used for compact cameras or dSLR macro photography.
• Ikelite DS-125 - Replaced by the DS-160, used for macro and wide-angle, one of the most popular strobes for dSLRs.
• Ikelite DS-160 - One of the top choices for dSLRs, fast, powerful, used for macro and wide angle.
• Ikelite DS-161 - Released in Dec 2009, same as DS-160 but includes a 500 lumen LED video light
• DS-200 - Professional level, made for wide-angle.

Inon Strobes

Excellent reputation for strobes, known for excelelnt build quality, small size, great S-TTL (optical TTL) feature which mimics a camera's preflash, and great power/size ratio. The Inon S2000 is their latest strobe.

• Inon S2000 - Brand new as of early 2009, could be the new top choice for compact cameras. Slightly smaller, cheaper, and almost as powerful as the D2000. Considered the "hot" new strobe for compact cameras. Takes 4 AA batteries. Guide # of 20. Retail price is around $450 USD. Read the Inon S2000 review
• Inon D2000 - This strobe has been a top choice for compact cameras over the last couple of years. It's fired by a fiber optic cable.
• Inon Z220 - Replaced by the Z240. great choice for dSLRs, fired by sync cord only.
• Inon Z240 - Outstanding strobe, small, powerful, great for compacts or dSLRs. See my Inon Z240 review.

Inon S-TTL

Inon S-TTL, also known as "optical" TTL, will allow you to shoot TTL without using a TTL converter, as long as the camera has it's internal flash firing, and the strobe can "see" the flash fire via a fiber optic cable. The strobe will mimic the camera's preflash. This type of TTL is becoming very popular in compact cameras, and is even spreading to dSLR's where the housing allows the internal flash to "pop up". Supposedly Sea & Sea has implemented something similar in it's YS-110a strobe, and YS-01 strobe, I'm still waiting to try one out.

Subtronic Strobes

Subtronic strobes are heavier and more expensive strobes, but some pro's swear by them for their soft light, power and even light coverage. If you have the money, and don't mind the extra weight, consider Subtronic strobes.

Saving money: Used & budget strobes

If you are on a budget, older YS-90s are good strobes with good strength and coverage, and can be bought fairly cheaply if you look hard enough. I’m guessing around $250. Ikelite DS-125's and Inon Z220's are also great, strong strobes that be bought used at good prices.

And if you are really on a budget, the Fantasea Nano strobe costs $105 new, and works well without a fiber optic cable, with most point and shoot cameras. I haven't tried the Intova ISS2000 ISTR Slave strobe, but I heard it's a good value for the money at $135, for macro shots. The Intova is also sold as the UltraMax Ultrapower UXDS-1 strobe.

You can also read about choosing the right arms and clamps.

Instructional Video tutorials on strobes

Video tutorial on using a strobe

Further Reading

White balance underwater

Color Temperature Underwater

Underwaer lighting with strobes - frontlighting,sidelighting,backlighting

Underwater Strobe position diagrams