Showing posts with label Tips. Show all posts
Showing posts with label Tips. Show all posts

Thursday, 18 June 2009

What time of day is most suited for under water photography?

In contrast to film and photography on dry land, where the best light is generally found early in the morning, or late in the afternoon, noon offers the best light for under water footage.

The reason for this can be found in the light filter properties of water. After only 1 m (3 feet) the ray of light passing through water has already noticeably lost some of is red colour spectrum.

And please note: We're not talking about dive depth in this case! If the sun is at an angle, that ray passes threough the water at an angle. i.e. if the afternoon sun hits the water at an angle of aournd 36°, then 3 ft of dive depth adds up for 5 ft the ray has to pass through the water to reach the object your're taking a photo of. The light is then refelected from the object an has to travel another 3ft or so to get to your lens. That totals at 8 ft of water to filter out that nice, warm red light at only 3ft dive depth!

For that reason we tend to use that time of day for our footage in which the light has the shortest distance to travel through the water on its way to our lens.

That is the time, when the sun is directly above and generally speaking
between 11:00 a.m. and 1:00 p.m.
(and if possible, at low tide...)


 The effects of water on the light spectrum

Wednesday, 17 June 2009

Flexible housings: What's that ? And how does it realy work?

 flexible camera housings and how they work

The biggest safety feature of a flexible ewa-marine housing is the fact that the air pressure inside the housing is always the same as the water pressure outside. As a result, there is no undue stress on any seal and no risk of an implosion. We are also able to use a thinner front port then comparable hard housings, thus reducing the otherwise resulting quality losses in the pictures.

The relationship between volume and pressure is described by the law of physics according to Boyle-Mariotte:

pressure x volume = constant

We have designed the housings with this in mind and have left enough air around the camera in an inflated housing for you to reach the depth we tested ourselves. The foam padding and valves supplied with selected housings help to ensure that the maximum amount of air can be included in the housing while allowing access to all the relevant controls.

Nevertheless, the volume is also the factor that determines the buoyancy. For that reason it might be preferable to reduce the amount of air in the housing for snorkeling. Also please keep in mind, that the housing will be very buoyant at the surface, but as you descend and the volume decreases, it will even develop a negative buoyancy (start to sink) with some heavier cameras or camcorders.

When you have reach the tested depth, all the air will have been pressed inside the camera or camcorder itself. If you continue your descent, the pressure sensitive parts will be affected first and at a very small pressure difference (shutter release, power, etc.), thus causing a malfunction of your camera or camcorder. Stop the descent immediately, return to a safe depth, and all will return to normal.
PLEASE NOTE:
There is a groove at the rear of the closing rail. As you submerge the housing bubbles will escape from this grove. This should last for about 1/2 Minute and before coming to an end. This phenomena is normal and has nothing to do with whether the housing is waterproof or not.