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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 Editor-at-Large for Scubaverse.com with responsibility for conservation and underwater videography. Jeff is an award-winning TV wildlife and underwater cameraman and film maker who lives in Cornwall, UK. With over 10,000 dives to his credit he has dived in many different environments around the world.

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Ocean Art 2020 Winners Announced!

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Ocean Art Contest Announces the Best Underwater Photos of the Year

The prestigious Ocean Art Underwater Photo Competition, organized by the Underwater Photography Guide, has announced the best underwater photos this year with its 2020 winners. Despite global travel restrictions and the challenges brought by the Covid-19 pandemic, the 9th annual competition attracted an extremely high caliber of photos from oceans around the world. Underwater explorers captured photos locally, in select destinations currently open to travel, or revisited their archives to bring us some eye-catching photography. This unique assortment of photos could not have been possible without the help of our generous sponsors who have all had to navigate a changing travel and dive industry. Many of these same sponsors helped the Ocean Art competition raise money earlier in this year to raise money to donate to the WHO and CDC in their fight against Covid-19. These photos showcase the perseverance of underwater artistry amidst the adversity of the times.

All the winning photos can be seen at the Underwater Photography Guide at https://www.uwphotographyguide.com/ocean-art-contest-winners-2020

The Best of Show is a once-in-a-lifetime moment of an octopus taking a selfie with the photographer and his curious family in the background. The photo was captured by photographer Gaetano Dario Gargiulo close to his home in the tide pools of Kamay Botany Bay National Park, New South Wales, Australia.  Other extraordinary winners include astonishing scenes of animal behavior, images that bring hope for the next generation of sea creatures, displays of ingenious photographic technique, and conservation scenes that reflect on not just the need to conserve our planet, but our species as well. The judges evaluated thousands of entries from 80 countries before selecting the final set of images as Ocean Art winners.

Ocean Art 2020 judges included prestigious underwater photographers Tony Wu, Mark Strickland, and Marty Snyderman.

Over $45,000 in prizes have be awarded, making the Ocean Art prize value among the highest in the world.

Ocean Art prizes are provided by some of the world’s top scuba diving resorts, liveaboard dive yachts, and underwater photo gear manufacturers. Grand prizes include a choice of 7 or 8 nights for two aboard the Coralia Liveaboard in Raja Ampat or Komodo, a 7 night liveaboard trip on the M.V. Bilikili in the Solomon Islands, a 7-night dive package with Villa Markisa, a 7 night dive package at Siladen Resort & Spa in Bunaken, a 12 night Passport to Paradise with Murex Dive Resorts and Lembeh Resort to three different Indonesian destinations, a 5-night dive vacation with AquaMarine Diving Bali & Ramayana Candidasa, a 7-night dive vacation at Atlantis Philippines Dive Resorts, and a variety of gift certificates from Bluewater Photo and Bluewater Travel. Premium travel prizes are provided by Volivoli Beach Resort (Fiji), Crystal Blue Dive Resort (Philippines), and Solitude Liveaboards & Resorts (Philippines and Indonesia). Premium gear prizes are provided by Sea & Sea and Ikelite. 12 different categories ensure a competitive contest for all levels and disciplines of underwater photography.

The photographic ingenuity from competitors is getting better every year – making judging very difficult and demonstrating that the winning images are some of the best in the world. Bluewater Photo and Bluewater Travel owner and Underwater Photography Guide publisher, Scott Gietler commented, “The Ocean Art team was thrilled to see that so many photographers were able to get out, dive, and immerse themselves in photography this year. The Best of Show was especially impressive. My only concern is that the octopus should get its share of the prize, as it did assist in taking the shot!” 

For more information, please visit http://www.uwphotographyguide.com 

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Gear Reviews

Gear Review: SeaLife SportDiver housing for iPhone (Watch Video)

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In a video shot exclusively for Scubaverse.com, Jeff Goodman reviews the SeaLife SportDiver housing for Apple’s iPhone, used with the Sea Dragon 2500 Light.

For more information about Sealife Underwater Cameras visit the website by clicking here

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