Crisp action photos require sharp focus, adequate depth of field and a shutter speed fast enough to eliminate motion blurring.

Linda Gettmann
Camas, Wash.

Film is merely an acetate base that has been coated with a light-sensitive emulsion. When a picture is taken, light (hopefully focused light) falls on the film in an amount determined by the lens aperture and camera's shutter duration. The result is a latent image, and when the film is immersed in a developer, the finished image (either a positive or a negative) results.

The light-sensitive component of the emulsion is comprised of countless tiny particles of metallic silver that form the image. These silver grains are typically microscopic, but they can clump together in certain films or under certain development conditions. When they clump to the extent that they become visible, the picture appears grainy.

Faster films are usually the most grainy. The higher the film's speed number, the more light-sensitive it is. Typical film speeds range from ISO 25 (very slow) to ISO 3200 (very fast). (ISO stands for International Standard Organization and is the same as the older term ASA--American Standard Association.) The two films you mention, Fujichrome Velvia (ISO 50) and Fujichrome Provia (ISO 100), are both slow films. Velvia in particular is extremely sharp, and when processed properly exhibits very little discernible grain. In fact, Kodachrome 25 and Velvia are considered the two finest-grain transparency films on the market. So, why would your editor complain about grain in a Provia or Velvia photograph? Processing variables may be the culprit.

Overdevelopment promotes clumping in even fine-grain films, which is why pushed films (extended time in the first developer to increase the effective ISO) will always generate additional grain. But it's a relative matter. Some professional photographers, among them nature photographer Galen Rowell and I, are so fond of the color and contrast characteristics of Velvia that we will commonly push them one stop when light conditions require a 100 ISO film. Grain does increase somewhat, but no more than that found in most 100 ISO films anyway. So, unless you are deliberately underexposing or significantly overdeveloping your photos, it is quite unlikely that grain will be a problem in either Velvia or Provia. Offer to clean dirt off your editor's loupe.

Jim Sommers
White Plains, N.Y.

According to photo author Andreas Feininger, "Sharpness is a psychophysical phenomenon ... one should only speak of 'apparent sharpness' because sharpness is always relative ... sufficiently magnified, even the sharpest negative, transparency or print becomes unsharp." Feininger talks about three kinds of sharpness:

1. Sharpness of focus. This is a function of whether your lens is accurately focused on your primary subject.

2. Sharpness in depth. This refers to the depth of field. Even if your primary subject is in crisp focus, shallow depth of field from a wide aperture may give the psychological impression of an out-of-focus photo.

3. Sharpness of motion. Your shutter speed must be high enough to eliminate subject motion or camera movement (unless you're after intentional blur).

Ideally, your pictures will be accurately focused and free of accidental motion. I find that most sharpness improvement in student work can usually be made by increasing the depth of field. Wide-angle lenses offer significant depth of field, but with normal and macro lenses it may be necessary to go to smaller apertures to achieve good depth of field. Try getting closer to the subject to enhance strobe efficiency (and smaller f-stops). Faster films will allow smaller apertures and consequently enhanced depth of field, but of course that may be at the expense of more grain.

Skittish creatures like this barnacle blenny are most easily photographed with an SLR camera and underwater housing.

Emilio Grenet
Miami, Fla.

You are correct in assuming that the SLR is a powerful tool for underwater photography, but don't discount the ongoing efficiency of your Nikonos V. Equipped with the 15mm or 20mm lens, the Nikonos V is an outstanding tool for wide-angle photography, and if the creature will tolerate the intrusion of a framer, the Nikonos V with extension tube or close-up kit shoots great photos of the reef's minutiae. But without dispute, the SLR is a better stealth tool for certain marine life, and by definition the view through the ground-glass lens will render more accurate compositions than via a separate viewfinder. So, if you are committed to SLR imaging for underwater photography, what is the best tool for you?

These days I'd say the minimal requirements include auto-focus capability, a built-in power film advance, and a through-the-lens (TTL) auto-exposure system. Any of the mainstream camera manufacturers like Canon, Nikon, Minolta or Pentax (to name just a few) offer sophisticated cameras and excellent optics.

Probably the most popular SLR for use in an underwater housing today is the Nikon N90s. Nikon has a strong history in underwater photography and has created considerable brand loyalty. In the early years of manual focus cameras, photographers were most often housing the Nikon F, F2s, and more recently F3s. When auto-focus technology appeared, housing manufacturers and consumers both embraced the Nikon 8008. The N90s is considerably more advanced than the 8008, and features a rapid, accurate auto-focus and accurate TTL exposures with most submersible strobe systems.

Several underwater housing manufacturers offer systems for the N90s. Aquatica forged an alliance directly with Nikon Inc. and now its A90 housing is marketed in the United States by Nikon. Sea and Sea, Ikelite, Nexus, Subal and SeaCam likewise have excellent housings for the N90s. Price, service, reliability and ergonomics should determine which housing is right for you.

Farewell to the RS?
I've seen several Nikonos RS cameras for sale. Should I go for it?

D.M.
Memphis, Tenn.

Actually, I own two RS cameras and will keep using them as long as I can. I especially love the viewfinder, ergonomic controls and excellent optics. But the reality is that they are now out of production, and at some point they will be difficult to repair due to lack of available parts. Plus, as time marches on, there is more advanced technology than that found in the RS. The RS was based on the Nikon 6006, and the auto-focus occasionally had trouble with low-contrast subjects. More modern cameras like the N90s and F5 are significantly more efficient in the auto-focus category. Rather than buying a used or even a new Nikonos RS (if you can find one), I'd say it's time to invest in the newest technology available.

The Sunny-16 Rule for topside exposure can help you interpolate underwater exposure values.

Technique: The basic Sunny-16 concept assumes a bright, cloudless day with the sun reasonably high in the sky (between 10 a.m. and 2 p.m.) and a front-lit topside subject. Under these conditions with the camera set at f/16, the shutter speed that will give you the correct exposure is most probably the reciprocal of your film ISO. For example, ISO 100 film at f/16 should require a shutter speed of 1/100th (or the nearest applicable shutter speed). ISO 400 film should be properly exposed at 1/400th second at f/16.

To prove this to yourself, set your camera at f/16 on manual exposure control. Stand with the sun behind your back and take a picture of a friend. Use ISO 100 slide film (the exposure latitude on print film is too great for the test to be valid). Do a series of exposure brackets as follows: 1/15th, 1/30th, 1/60th, 1/125th, 1/250th and 1/500th second. The fourth shot in the series, 1/125th second shutter speed, should be the best exposure of the series. If not, figure out why:

1. The shutter speeds on the camera could be miscalibrated.

2. The aperture blades could be sticking. Modern cameras view at maximum aperture for the brightest possible image on the ground glass. When they must stop down to a small aperture like f/16 at the moment of exposure, overexposure may result if the diaphragm is sluggish and closes too slowly.

3. Film processing: Maybe the film had too much or too little time in the first developer, maybe the temperature in the chemistry was not accurate, or perhaps the chemicals were not fresh.

I often use the Sunny-16 guideline as a meter check as well. Let's say I'm shooting breaching whales but the combination of dark water and light sky is giving my meter erratic readings. There is no chance to bracket exposures. I know I want a shutter speed of at least 1/500th of a second to stop the action. My Sunny-16 value for a standard shutter speed with ISO 50 film is 1/60th at f/16. Which is the same as 1/125th at f/11, 1/250th at f/8, or 1/500th at f/5.6. If my meter is not showing approximately f/5.6 while set at 1/500th second, I may choose to expose by instinct rather than trust the meter.

"If you're traveling with film and a camera, keep them with you and don't check them in," advises Tom Dufficy of the Photographic and Imaging Manufacturers Association, which represents Fuji, Kodak and others.

The warning was issued following tests at an FAA research center on color film using one of the new generation of scanners. The scanner damaged all brands and all speeds of the film tested, causing it to lose color and appear grainy. The faster the film's speed, the greater the damage.