Procedures for Macro Underwater Photography.

Macro photography is extreme close-up impression in which the image captured on film is the same size or larger than the subject being photographed. It can mean subjects Underwater are enlarged on the film by one-half to one-third the size of the subject.
In the case of a range finder camera like the Nikonus V system, the lens is usually extended with a tube. This changes the depth of focus between a half inch or smaller. By using a framer system, the viewing plain of the wire guides help judge what will be in focus. Next is the f-stop is set at the upper end to allow the greatest depth of field and the strobe is used to change the exposure by moving the flash forward or backwards. When selecting subjects and background keep the proportions of the area as two-thirds subject matter and one-third space of background. Creating flat images is simple and creating impressions that illustrate a perspective of depth and angles takes practice. Changing the angle of the strobe to the subject can create shadows to add contrast. In changing the ISO setting by half the exposure is increased to let more light in. If a subject is bright with a bright background the adjusting of the strobe further away or increasing the ISO will prevent overexposure.
A good practice session of the 35 millimeter lens and the 1:1 extension tube is to photograph a strawberry in sand out of water setting up a test series of angles to image, distance and angles of strobe, changing the ISO setting and changing the backgrounds to those seen Underwater. When using 1:2 extension tubes increase the subject to a orange or apple. Take a series of pictures changing only one thing. This will help create a guide in judging what technique to use with a subject and background combination when on a dive.
When using a housed SLR with a Telephoto lens which allows viewing of subject, the exposure will cause the greatest lost of images will be due to lighting by subject versus distance to strobe. Be sure to bracket a series of pictures by adjust the strobe backwards to decrease exposure. This type of system is hardest to use when trying to look through the viewfinder and follow a moving fish. Practice out of water with a flower and a butterfly combination. Trying to wait for the butterfly to land and spread the wings and get the shot before it decides to fly away is very time consuming. There will be many picture attempts trying to get the photo, this is the same as trying to capture a reef fish on the right sponge composition or color.

Selection of objective when using Macro Photography will prevent wasted time Underwater. Without practice out of water and learning what will happen with different settings, the odds of obtaining an awesome impression will be very rare.
Remember Underwater Photography starts as skill development, then composition followed by technique and finely artistic realization.