EXTRA
November 1999
HEAD to HEAD:
|
EXTRA
November 1999 HEAD to HEAD: |
  
|
The microchip has revolutionised photography. Now you can dive with a camera that allows you to look through the lens to compose the picture, deduces the correct exposure through multi-segment assessment and combines that with use of fill-in flash. Focus is automatic, and anyone can get good results. My percentage of usable shots per roll has increased three-fold since I swapped to a Nikon F90 in a housing. Through-the-lens composition is essential for macro photographers. Some wonderful images have been secured using the Nikonos V, extension tubes and some sort of image-framing device, but more active subjects don't allow such an intrusive approach and the SLR in a housing lets you work from a distance. You can also remove the housing and use it topside. However, camera and housing are bulky to transport and for wide-angle photography the choice of camera is less clear-cut, especially as the all-up price is similar. The Nikonos V wins on portability. Even with a large-diameter wide-angle lens, it's hardly bigger or heavier than a standard surface camera. But it has only a puny direct-vision viewfinder, which you must look through to adjust the semi-automatic exposure control, and then you have to switch to a separate top-mounted viewfinder matched to the wide-angle lens in use. You have to wind on the film manually, which means reframing between shots, and must estimate and set the focusing distance manually, too. If you use flash, the camera works at one fixed shutter-speed of 1/90sec (slower in manual mode), too slow to catch your average shark. There is no automatic way of getting the flash and daylight exposure right every time. So portability apart, why would anyone use a Nikonos V? Well, all but its 35mm lens are designed to work with the front element in contact with water, not air, and under water the lens quality is unsurpassed. Sea & Sea also makes high-quality prime lenses for the Nikonos, cheaper but with a smaller usable maximum aperture and reduced low-light capability. Estimating and setting the distance manually on the 15mm lens is not a problem because there is such a dramatic depth-of-field. At f/5.6 everything from 0.5m to infinity remains in focus, across the frame from edge to edge. That doesn't happen with a housed camera. Rarely is the front node of the SLR's lens positioned in such a way that the image is sharp from side to side, and a different set of rules for depth-of-field applies. However, if you're careful to position the cross in the reflex viewfinder over the relevant part of the subject when you first depress the shutter-release button, focusing is automatic. The 20mm Nikkor on the Nikon behind a dome port has an angle of view equivalent to the Nikonos V with the 15mm UW Nikkor or Sea & Sea lens in contact with water. Even fitted with a superior Nikon prime lens, the image sharpness of the housed camera will not be as good - and that's when it's positioned behind the largest possible diameter dome. Some small domes need a strong-dioptre close-up lens to the prime lens so that it can focus on the very near virtual image produced but this reduces quality. A large dome port puts the virtual image at a more agreeable distance so that at least you can use the lens without compromising it in this way. However, modern SLRs like the Nikon F90 can be used synchronised with flash at 1/250sec, which goes a long way towards solving the second reason for unsharp pictures - camera or subject movement. Conducting a dive with your eye glued to a reflex camera in a substantial housing has its advantages. I have coped with many hazardous situations with animals by watching them on the viewing screen - psychologically it puts a barrier between us. However, caught in the middle of a feeding frenzy of sharks or the acrobatics of a family of sealions, it takes around 1/25 sec for the Nikon SLR camera to get its reflex mirror out of the way and record an image. You can miss those moments you would have captured with the direct-vision viewfinder and instant response of the Nikonos V. The film leverwind of the Nikonos V can be distracting and you often lose count of the number of frames remaining. The powered film-transport of the modern Nikon SLR makes removing the camera from your eye unnecessary, and the viewfinder display tells you how much film is left. The multi-segment matrix metering of the Nikon SLR can also integrate the daylight exposure needed with that of the flash, to give very natural-looking flash-and-daylight pictures. With the Sea & Sea NX90Z housing you can even use two compatible flashguns to make the lighting subtler still. It's all down to microchips. The Nikonos V uses a rather old-fashioned method to meter available light, taking an integrated reading of the light falling in only the lower part of the image. This can lead to inaccuracies, especially when using wide-angle lenses which have their rear element close to the film plane. Many Nikonos V users persevere by estimating the exposure separately and setting it manually. They bracket the exposures half a lens stop either way, so getting only 12 out of 36 properly exposed pictures on a roll. What's really needed for wide-angle underwater photographs is a Nikonos V with its superior underwater optics and instant response combined with the sophisticated electronics of the Nikon SLR. This would give it the ability to get the exposure right even when combining daylight and flash, the faster shutter speeds possible with flash, and the powered film transport. The Nikonos V with 15mm Sea & Sea lens and viewfinder costs £1379. With 15mm UW Nikkor it costs £3122. The Nikon F90X with 20mm Nikkor in a Sea & Sea NX90Z or Aquatica 90 housing (with dome port that needs no CU dioptre accessory lenses) costs around £3000. Flashguns are extra. |
  
|
