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Photo / Video News & Reviews

A Guide to Underwater Wildlife Video & Editing: Part 6

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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.

lenses

B

lenses

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.                     

lenses

Telephoto lens

                                                           

With a standard lens you can see that the depth of field, with all other factors being equal, will be far greater.

 

lenses

Standard Lens

lenses

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.

Jeff Goodman is the Conservation editor and also the Underwater Videography Editor for Scubaverse.com. Jeff is an award winning TV wildlife and underwater cameraman and film maker. With over 10,000 dives to his credit he has dived in many different environments around the world.

Marine Life & Conservation

Exhibition: Protecting UNESCO Marine World Heritage through scientific research

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From now until 30 October, the photo exhibition “Protecting UNESCO Marine World Heritage through scientific research” features 21 photographs at UNESCO Headquarters, Paris, as well as a digital edition.

Exceptional photographs highlight how innovative marine experts and scientists take the pulse of the ocean by exploring ecosystems, studying the movement of species, or revealing the hidden biodiversity of coral reefs. Scientific discoveries are more important than ever for the protection and sustainable conservation of our Marine World Heritage. This memorable exhibition comes ahead of the launch, in 2021, of the United Nations Decade of Ocean Science for Sustainable Development (“Ocean Decade”). The exhibition was jointly developed by UNESCO and the Principality of Monaco.

The 50 marine sites inscribed on the UNESCO World Heritage List, distributed across 37 countries, include a wide variety of habitats as well as rare marine life still largely unknown. Renowned for their unmatched beauty and emblematic biodiversity, these exceptional ecosystems play a leading role in the field of marine conservation. Through scientific field research and innovation, concrete actions to foster global preservation of the ocean are being implemented locally in these unique natural sites all over the world. They are true symbols of hope in a changing ocean.

Since 2017, the Principality of Monaco supports UNESCO to strengthen conservation and scientific understanding of the marine sites inscribed on the World Heritage List. This strategic partnership allows local management teams to benefit from the results obtained during the scientific missions of Monaco Explorations. The partnership also draws international attention to the conservation challenges facing the world’s most iconic ocean sites.

The exhibition invites viewers to take a passionate dive into the heart of the scientific missions led by Monaco Explorations in four marine World Heritage sites: Tubbataha Reefs Natural Park (Philippines), Malpelo Fauna and Flora Sanctuary (Colombia), Rock Islands Southern Lagoon (Palau), and the Lagoons of New Caledonia: Reef Diversity and Associated Ecosystems (France). It is also an opportunity to discover the work of a megafauna census; the study of the resilience of coral reefs and their adaptation in a changing climate; the exploration of the deep sea; and the monitoring of large marine predators through satellite data.

To visit the Digital Exhibition click here.

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Blue O Two announce the winners of DIVING LIFE Photography Competition

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Blue O Two has announced the winners of their first amateur photography competition.  Entitled, DIVING LIFE, it had two categories: Underwater Photograph and Divers Lifestyle Photograph.  An overall winner was chosen from the two category winners and received the title: Diving Life Photographer of the Year 2020.  A calendar of the winning photographs is being produced and will be released for sale in the coming weeks. 

The team at Blue O Two were blown away by the response they had to the competition.  Entries came in from all over the world.  When they launched the competition, it was in part to lift the mood, spreading some joy among the Covid gloom.  The idea was to remind divers of wonderful past experiences and to dream of those they will have again.  Given the engagement from the global diving world and the standard of entries, the competition will now be annual.

Ivan Donoghue: There’s always one!

From the hundreds of entries, there was an initial shortlist of 50 images.  Each category had 2nd and 3rd places, alongside several runners up.  The overall winner has a Liveaboard trip to Egypt to look forward to, the title of ‘Diving Life Photographer of the Year 2020’ and an assortment of Blue O Two goodies. Both category winners will receive a copy of their photograph printed on canvas, a copy of the Diving Life Calendar 2020 and a selection of branded goodies. The runners up will have their image printed in the calendar and will receive a free copy.

Dr Alex Mustard MBE, who judged the competition, said the following: “This collection of fabulous winning images reminds me why I love being underwater and going on diving adventures. It was a tough contest to judge because it was more than just an underwater picture competition, Diving Life was created for amateur photographers to share their love of diving, with pictures taken both above and below the surface. When judging I gave equal weighting to the feeling captured in the images and their photographic technique and quality. For me, all the winners capture the highs of dive trips: encounters with incredible creatures both big and small, amazing moments underwater, spending time with friends, visiting incredible places and having fun.

Overall Winner: Masayuki Agawa with Hammer River

Special congratulations to the overall winner Masayuki Agawa from the USA, whose white knuckle image Hammer River will immediately transport anyone who has dived with hammerheads in the East Pacific back on those dives. The hammerhead schools are regularly most spectacular when the currents are fierce and the advice from the National Park guides is to stay low and hold onto the rocks, as anyone floating up in the water will spook the sharks. The picture places me right in the moment of this unforgettable experience as the hammerhead school magically materialises from the blue.”

The winner, Masayuki Agawa, said: “I am truly honored. Thank you very much for the compliments! It was hard to contain my excitement when I saw the announcement.  Thank you again for such opportunity and motivation. I will continue to strive for better photos in the future!”

To see the winning images and learn more about the competition click here.

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