News
A Guide to Underwater Wildlife Video & Editing: Part 6
Read Part 5 here.
A part serialisation of a book by Jeff Goodman
PART 6: Lenses, Depth of Field, Angle of Coverage
I guess one could write a whole book on lenses, their applications and relationship with exposure i.e. shutter speeds and aperture (f stops) and depth of field, but for the sake of this guide I will just cover the basics. And I do mean the basics.
A rule of thumb with taking a lens underwater is that because of the different refractive index of water to air, the angle of coverage of the lens will decrease by 1/3rd as soon as it is submerged, as the diagram shows.
B
A
A 90 degree lens (A) on land is only going to cover 60 degrees (B) underwater. So what are the implications of this?
Because of the nature of filming underwater and the probability of there being some sort of debris affecting visibility, then it is generally preferable to get as close to the subject as possible to get a good crisp, clear picture. Hence the general use of wide angle lenses rather than standard or telephoto.
What has this to do with focus and depth of field? First of all what is depth of field? Looking at the diagram we see a telephoto lens focused on an object at a distance of say 3 metres. Taking an average exposure and thinking purely in generic terms, an object (A) placed say 3 metres away when focused upon will of course be sharp. The area marked in front and behind the object will also be sharp. So the depth of field is taken as the distance between points B and C. Everything outside of that area will be out of focus.
Telephoto lens
With a standard lens you can see that the depth of field, with all other factors being equal, will be far greater.
Standard Lens
Wide Angle lens
With a wide angle lens the depth of field is greater still and will probably be from the lens front to infinity. This does vary depending where the focal point A is in the first place and the f stop of the lens, but generally the wider the lens the greater the angle of coverage and the greater the depth of field.
So for underwater work a wide angle lens is greatly preferable to any other as it allows you the possibility of getting close to your subject and maintaining a good depth of field.
Please do look up ‘depth of field’ if you want more information on how this all works, but generally, depth of field is governed by the aperture (or f-stop) of the lens and this aperture is directly affected by the shutter speed, which in turn is affected by the gain. The slower the shutter speed the smaller the aperture of the lens can be and the smaller the aperture the greater the depth of field. But, if your shutter speed becomes too slow, say less than 1/50th of a second then your video images may start to take on a blurry look. Ideally a 1/50th to 1/60th is good. Auto exposure will balance these three items against each other to give you the best overall exposure.
Higher shutter speeds are good for capturing fast action with nice sharp results, but the penalty you pay is the overall loss of light through the lens. This means that the aperture will have to be larger to let in more light to give a good exposure and that in turn will reduce the depth of field.
Starting to get a little cross-eyed? Don’t worry about it unless you are going to take up videography in some professional way or you really want to know what is going on in your camera. Otherwise be content with simply adjusting the ‘exposure’ dial until the picture on the monitor looks good.
Next time we look at Flat and Dome Ports.
Whether you are a beginner or a professional diver – with the three new main regulators from DYNAMICNORD, everyone will find their favourite regulator. They all look super stylish.
Excellent performance with the TR-80
Quality and performance are the be-all and end-all for regulators. It is not for nothing that the TR stands for Tec Reg. The innovative design of the TR-80 guarantees absolute reliability – even in ice-cold waters.
Perfect breathing effort at 0.8 J/l / certified for diving in waters below 10 degrees / structural design made of solid brass for best cold protection / membrane-compensated design with dry seal of the first stage / reduced exhalation effort thanks to optimized exhalation membrane and bubble deflector / adjustable Venturi (dive/predive) and adjustment knob for individual inhalation comfort / innovative design of the front cover prevents free-flow in strong currents or when diving with scooters / design made of sandblasted brass, matt chrome finish / 2 HP and 4 LP outlets / mouthpiece made of high-quality, anti-allergic silicone for maximum comfort.
Amazing underwater adventures with the IR-50
The IR-50 is the top regulator for advanced and experienced divers. Natural breathing is the essence of this regulator.
Ideal breathing effort at 0.8 J/l /certified for diving in waters below 10 degrees / compensated membrane / adjustable venturi (dive/predive) and adjustment knob for individual inhalation comfort/ outlet valve and deflector for minimum exhalation effort and reduction of bubbles on the face / design made of sandblasted brass, matt chrome finish / 2 HP and 4 NP outlets / mouthpiece made of high-quality, anti-allergic silicone for maximum comfort.
The Workhorse – our CS-30
For diving centres and diving beginners – the workhorse stands for strong construction, reliability and robustness. Perfect for your training.
Optimal breathing effort at 0.8 J/l /recommended for diving in waters above 10 degrees / non-compensated piston / adjustable venturi (dive/predive) / outlet valve and deflector for minimum exhalation effort and reduction of bubbles on the face / design made of sandblasted brass, matt chrome finish / 1 HP and 3 NP outlets / mouthpiece made of high-quality, anti-allergic silicone for maximum comfort.
Octopus OP-30
The OP-30 is the ideal addition to all DYNAMICNORD regulators. It is identical in construction to the CS-30.
The TR-80, IR-50, CS-30 (DIN & INT) regulators and the Octopus OP-30 are available from DYNAMICNORD dealers and in the online store.
DYNAMICNORD – Your Outdoor Companion.
Renowned anti-whaling activist Paul Watson has been released from custody in Greenland after spending five months in detention. Denmark’s Justice Ministry rejected Japan’s request for his extradition, citing insufficient guarantees that his time already served in custody would be credited against any potential sentence.
The 74-year-old Canadian-American was arrested on July 21 in Nuuk, Greenland’s capital, when his ship docked to refuel. His arrest was based on a 2012 Japanese warrant related to a 2010 encounter in Antarctic waters. Japan alleged Watson obstructed operations and caused damage to a whaling research ship during efforts to disrupt illegal whaling. Watson has consistently denied these claims, maintaining his commitment to marine conservation.
Denmark, which oversees extradition matters for Greenland, concluded that while the legal conditions for extradition were met, the lack of assurances from Japan regarding time-served credit made extradition untenable.
In a video shared by his foundation, Watson expressed gratitude and relief, saying, “After five months, it’s good to be out… and good to know they’re not sending me to Japan.” He added that the most difficult part of his time in custody was being separated from his two young sons.
Watson is a pioneering figure in marine conservation, known for founding the Captain Paul Watson Foundation in 2022 after decades of activism with the Sea Shepherd Conservation Society. His bold efforts to defend marine life have earned him widespread support, including from celebrities and conservationists. His work has also been featured in the acclaimed reality TV series Whale Wars.
Watson’s lawyer, Jonas Christoffersen, praised the decision, stating, “We are happy and relieved that Paul Watson is now free.” He added that Watson is eager to reunite with his family and continue his vital work.
The arrest occurred while Watson’s vessel, the M/Y John Paul DeJoria, was en route to the North Pacific with a team of 26 volunteers to intercept a Japanese whaling ship. His foundation described the arrest as politically motivated and emphasized that Watson’s actions were focused on ending illegal whaling practices.
Japan resumed commercial whaling in 2019 after leaving the International Whaling Commission, asserting that whale meat is a cultural tradition. Conservationists, however, continue to challenge these practices, highlighting their impact on marine ecosystems.
Despite the challenges, Watson remains steadfast in his mission to protect marine life and bring attention to whaling practices. His dedication to ocean conservation has made him a globally respected advocate for the environment.
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