Sunday, 18 October 2009

Nikon D300 underwater photography

Nikon D300 underwater photography tests with sailfish
Sea & Sea released us an early version of their MDX-D300 underwater housing for the Nikon D300 just in time for my sailfish expedition on December 31, 2007. Personally, I was really hoping for their MDX-D3 housing for the NikonD3, but I was thrilled to have the opportunity to put the Nikon D300 and Sea & Sea MDX-D300 through a real world test.

Sailfish were a perfect test subject for the Nikon D300. These fish torpedoes require smooth camera pans and a shutter speeds of 1/250th to capture sharp frames. At such high shutter speeds, I was required to shoot at ISO 400 or greater to maintain apertures of f4 to F5.6. The new low noise CMOS sensor in the Nikon D300 was a perfect match. I brought my higher megapixel Nikon D2x as backup, but it never got wet. Our expedition was unlucky with weather, but the Nikon D300 and Sea & Sea MDX-D300 housing performed flawlessly.

ISO 400 settings very smooth
Blue light is the most challenging tone for all digital capture devices. Deep blue tones typically exhibit the most noise of any color channel. As with topside photographers that shoot at twilight, we underwater photographers are unfortunately pushing the limits of available digital technology. Based on my tests, D300 files shot at ISO 400 are as good or better than ISO 100 shots from the Nikon D200 and D2x. I was thrilled with the smooth gradients at ISO 400, but found noise creeping in at ISO 800. That being said, ISO 800 shots were on par with ISO 400 from previous Nikon cameras. My topside tests with the Nikon D3 have me confident that it will deliver even better high ISO performance. I can’t wait to get the D3 wet, but the D300 is clearly a significant leap forward for underwater photography in a low cost, compact Nikon SLR. I’m quite certain I’d never get film scans this clean at ISO 400.

Accuracy required with exposure settings
As with all digital cameras, you must shoot accurate exposures with the D300 to avoid the noise enhancing effects of brightening a dark image in post processing. Poor exposure at higher ISO settings is a significant penality. Use the RGB histogram to push your exposure setting as bright as possible without clipping highlight detail.

Avoid sharpening during Raw Conversions
Some people choose to apply a small amount (25%) of sharpening during raw conversion. I found that any amount of sharpening was detrimental to the smoothness of blue gradients during raw conversions and would highly recommend only selective (masked) sharpening on the final output file.

Saturday, 18 April 2009

Australia Destinations Diving

Australia offers a wealth of travel experiences, from the drama of the outback and the diving spectacle of the Great Barrier Reef to the cosmopolitan city of Sydney and arguably the best beaches in the world.
Australia is an enormous country, and visitors expecting to see an opera in Sydney one night and meet Crocodile Dundee the next, followed by whale shark excursions in Western Australia the next, will have to radically re-think their grasp of geography and perspective of distance.

For example, Sydney to Cairns is approximately 2700 km (1700 miles), the same distance as Boston to Miami, or London to Athens. East to West is even further with Sydney to Perth being a 4 hour flight, similar to Los Angeles to New York, or London to Cairo.

Australia is big and it is empty. Only 19 million people live in an area the same size as the United States or half as big again as Europe. Most of these people live in a handful of coastal cities.

It is this sheer vastness, and the friction between the ancient land steeped in Aboriginal lore and the New World culture being heaped upon it, which gives Australia much of its character.

Monday, 30 March 2009

MDX-D300 housing viewfinder options

MDX-D300 housing assembly, feel and finish
The Sea & Sea MDX-D300 has a very solid feel in the hand and its in water weight seems lighter than the Sea & Sea DX-D200 housing. Unlike the previous cast model, the MDX-D300 is milled from a solid block of aluminum and thus has a more rugged finish. It survived 2 weeks of very poor maintenance (fresh water rinses out of a gas can) and cleaned up easily with no signs of corrosion or fatigue. The quick lock camera tray makes camera installation easy, but when using a zoom lens, it's best to wiggle the zoom knob prior to locking down the tray to ensure a precise install.

MDX-D300 housing viewfinder options
Personally I find all stock viewfinders on underwater housings to be difficult if not impossible to use for accurate composition and focus verification. The stock viewfinder on the Sea & Sea MDX-D300 is no exception. I received the housing hours before departure and was unable to install the new Inon Straight (180) viewfinder and chose to use the Inon 45 viewfinder instead. The Inon 45 offers a bright crisp image with the largest angle of acceptance, but I found the 45 degree angle (head down) view to be difficult for the fast action of sailfish and dolphin. I brought the stock viewfinder along, but determined I'd rather have the large view of the Inon 45. I was able to adapt my technique over the period of a few days and would now like to travel with both the 45 and 180 viewfinders and swap based on my subjects.


MDX-D300 housing control ergonomics
The Sea & Sea DX-D300 housing features oversized knobs and buttons that are easily controlled with even gloved hands. Essential controls (shutter release, aperture, shutterspeed, and focus lock) are easily reached with a large hand, but small handed users will likely find essential controls more difficult with only one hand supporting the housing. The round and non-indexed knobs for MSC and AF-area Mode require practice to accurately adjust on the fly, but unlike myself, most users don't regularly access these controls. The unique barrel style control for the Sub Command Dial (aperture) is very convenient, but is half occluded by the Fisheye Dome Port when not using an extension ring. While I’m quite fond of the smoother controls and ergonomics of the Subal line of underwater housings, I was able to operate all controls on the MDX-D300 quickly within 15 minutes of the first dive. The last Sea & Sea housing I personally shot was their Nikon F5 underwater housing and it was a personal favorite. This new line of MDX housings is a great step back to their previous attention to detail. Hat’s off to the new design team at Sea & Sea!

Friday, 20 March 2009

Australia Dive Master Rescue

Cairns is one of the most popular places in the world where people learn to dive during their holiday. Dive schools in Cairns usually have regular open water classes with many students.

For those who want to become dive professionals, it is the ideal place to learn how to teach diving as there are so many students learning each day. Safety comes first. But also quality and efficiency are to be learned here. To assist an instructor in a large open water class prepares you well for "the real life" out there.

Taking a divemaster course in Cairns is a great way to gain experience. Also, it is a good base if you wish to continue to an instructor course. Most courses offered in Cairns are PADI courses. The course is at least 18 days long, but plan for 21 days, to be on the safe side. Part of the course is to assist an instructor in teaching 2 Open Water courses. When available you may also assist in Advanced and Rescue courses.

You get 2 live aboard dive trips (each 3 days/2 nights long) to the Great Barrier Reef. During these trips you will get up to 20 dives. Some are training dives and some just recreational dives.

During the course you get familiar with the diver training process and you will gain an awareness of typical student problems. Also you will learn how to supervise and control divers in general. You will learn to perform diving skills to demonstration level and, of course, you learn a lot of theory and take written exams. You need to be pretty fit too, as there are a few swimming tests.

Minimum requirements are:

  • You should be at least 18 years old
  • Have a PADI Rescue Diver certification
  • A valid diving medical to Australian standard
    more details on dive medicals
  • No less than 20 logged Scuba Dives when starting the Divemaster course, but to complete the PADI Divemaster certification you will need to have completed 60 logged Scuba Dives.
  • Price for the 18-day Divemaster Course costs up to AU$ 1995 (until 31 March 2009). Please e-mail us if you are interested in this course.

Wednesday, 4 February 2009

THE OCEAN FLOOR

The ocean floor is home to many unique communities of plants and animals. Most of these marine ecosystems are near the water surface, such as the Great Barrier Reef, a 2,000-km-long coral formation off the northeastern coast of Australia. Coral reefs, like nearly all complex living communities, depend on solar energy for growth (photosynthesis). The sun's energy, however, penetrates at most only about 300 m below the surface of the water. The relatively shallow penetration of solar energy and the sinking of cold, subpolar water combine to make most of the deep ocean floor a frigid environment with few life forms.In 1977, scientists discovered hot springs at a depth of 2.5 km, on the Galapagos Rift (spreading ridge) off the coast of Ecuador. This exciting discovery was not really a surprise. Since the early 1970s, scientists had predicted that hot springs (geothermal vents) should be found at the active spreading centers along the mid-oceanic ridges, where magma, at temperatures over 1,000 °C, presumably was being erupted to form new oceanic crust. More exciting, because it was totally unexpected, was the discovery of abundant and unusual sea life -- giant tube worms, huge clams, and mussels -- that thrived around the hot springs.


tube

Friday, 2 January 2009

Temperature, Heat Capacity and Heat Conductivity

Temperature, Heat Capacity and Heat Conductivity The heat capacity of seawater is 3134 times greater than that of air. Water has insignificant heat conductivity. That is why distribution of heat to greater depths is very slow and is mainly achieved through convection.
The highest temperature of water is registered to occur between 3 and 4 p.m., and the lowest – a couple of hours after sunrise. There are three temperature layers of seawater: surface layer (epilymnion), intermediate layer (metalymnion), and deepest layer (hypolymnion). The thickness of the former two layers varies with the weather, season, and currents. The temperature of the surface layer is almost constant, being between 19 and 25ºC in the summer. As the deepest layer begins, temperature drops by a few more degrees and it remains constant thereafter (7–9ºC). That is the temperature of sea depths and it does not depend on the season.
Water Motion Water motion constitutes sea currents and waves. The reason for the formation of currents might be the different density of water, constant winds, etc. Ocean currents are usually caused by constant winds, whereas local ones are mainly due to the character of coastlines. According to he direction of their flow, currents can be classified as vertical or horizontal. There are three main types of waves: wind waves, standing waves, and seismic waves.
Wind is the main reason for the formation of waves. The process of wave formation can be divide into different stages. When the speed of wind is less than 1m/s, air motion does not affect the surface of the water. If wind intensifies, these rows of waves become irregular and peaks appear, which are due to the different pressure at the front and at the back of the wave. At a greater speed of wind large waves are formed, running in parallel rows. Th largest waves reaching hundreds of meters continue even when the wind has ceased. They create the so-called dead drift.
Standing waves are formed when the level of the water rises at one coast and in the same time drops at the other. A sudden decrease of atmospheric pressure at one of the coasts, appearance of strong wind or heavy rain can all be the causes for standing waves. The fluctuation of the sea level may reach 80cm, which is dangerous for vessels at the harbors.
Seismic waves are formed because of underwater earthquakes. A vessel that is nest the site of the earthquake experiences a hydraulic blow which is why old maps frequently contain non-existent reefs. Seismic waves are often present in the Hawaii region where they have the special name zunami. Such waves are formed in the Pacific Ocean, the Mediterranean, the Caribbean Sea, and the Malaya Archipelago as well. Sometimes, these waves reach the height of 35m and are dangerous not only for the ships but also for the native population because of their destructive power.Waves change their form when they reach shallow regions. When the depth becomes equal to the height of the wave, the water particles no longer move in a circle: their orbit becomes elliptical. The length of the waves decreases and the height increases. The front slope of the wave becomes vertical, the top is inclined forward, then it falls and eventually destroys the wave. This phenomenon is called a surf. Its force may reach up to 38 tonnes/m2.
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