By Michel Gilbert & Danielle Alary
When we first began taking pictures underwater there was nothing even close to automatic underwater flash photography. To this day, we swear by pool tests, exposure tables…and histograms! Is this about to change? With our ‘manual only’ attitude, we put the Ikelite TTL adapter to the test.
TTL – What’s In It?
The term TTL was coined long before it applied to flash photography. Literally, it means “through the lens”. TTL came about when camera manufacturers began installing built-in light meters in their cameras.
Strobe manufacturers started to equip their flashes with sensors to measure reflected artificial light and quench the strobe when proper exposure level was achieved. These were called ‘automatic’ strobes. Some even came with remote sensors that could be attached to a Nikonos or a camera housing instead of directly to the strobe itself.
In the mid-70s, Olympus developed TTL automatic flash exposure by moving the sensor behind the lens. Other manufacturers followed suit and TTL came to mean through the lens automatic flash measurement.
Measuring strobe illumination through the lens made more sense: it took into consideration the true amount of light falling on the film. This was decades before digital photography.
Fast forward to 2013: Digital TTL automatic flash exposure – a.k.a. TTL – is ubiquitous in the dSLR world. On land, TTL rules. Underwater, many people claimed great results, but we’ve been reluctant to adopt this approach.
So, recently we asked our friends at Ikelite to loan us one of their Nikon iTTL adapters. This nifty device connects the housing sync bulkhead to the strobe sync cable. It incorporates circuitry meant to interpret the ‘Nikonese’ spoken by the camera and translate it into ‘Ikelitish’, the idiomatic digital dialect of the DS strobe family.
From Skeptics to Believers
Mounting this setup on a Nexus housing would show us if it could deliver images rivaling our manual flash exposure pictures.
The adapter has two settings: iTTL or Manual. You toggle between them by turning a rotating switch that circles the adapter, an action easily done even with thick coldwater gloves.
The adapter only works with Ikelite DS strobes. It is connected using a Nikonos or Ikelite-type bulkhead sync port on the housing (specify bulkhead type with your order). The cable between the adapter and the strobe head must also be a 5-pin ‘digital’ type. A single adapter can be connected to two strobes using Ikelite’s ‘Y’ cable.
Our test strobes were the DS-125 and DS-51. During the dives, the camera’s LCD screen displayed nice images but the critical and only true test would come from the dreaded 30-inch monitor!
Back in the studio, within the first few images we went from skeptics to believers. Picture after picture the results were excellent, if not perfect. Even high-contrast subjects were well exposed and needed minimal post-processing.
All these test images were macrophotography or fish portraits, the perfect subjects for TTL flash photography.
How About Light Control?
We swear by manual strobe exposure for one main reason: control – full control – of each flash output. Using the iTTL adapter did present a challenge for us in this regard.
Although it is possible to perform flash compensation on Nikon dSLRs, this operation requires access to a button that is not present on our housing; however, it would be if we had an Ikelite housing! In our case, the easiest way to compensate was to put the camera in auto-bracketing mode, programming it to perform only aperture changes. This allowed compensation whenever the histogram showed an over or underexposure. It was by far the faster way of doing this.
If your housing does have a flash compensation button, be aware that compensation applies to both strobes together, and not on an individual strobe basis. To accomplish individual strobe compensation we varied the distance of one strobe until it underexposes by a slight margin.
Worth noting: if you buy an Ikelite housing, you already have a built-in Nikon or Canon TTL adapter. There is also a built-in compensation circuit activated directly on the housing. Compensation is possible in TTL or manual mode. This feature alone greatly increases the value of an Ikelite enclosure for your dSLR.
Are We Convinced Yet?
After more than 20 dives with the iTTL adapter we came to trust it. Danielle even made a decision: instead of sending the loaner back to Indianapolis she sent a cheque!
As expected, the iTTL adapter performs very well in macro and fish portraiture. For wide-angle, manual strobe exposure still remains our favourite method.
From now on, TTL flash exposure will be part of our underwater approach. It’s proven reliable and we see that it will be especially valuable when the need for speed arises. We’ve all come to expect the unexpected on a dive and this technology will help in these situations.
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