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Nikonos IV-A. enlarge
You can try to find this used at Adorama. It helps me keep adding to this site when you get yours from that link, too. This one was donated to me by Daniel in Sedona.
This is the classic Nikon underwater camera. It's built like a tank and needs no additional housing for depths to 160 feet (50m).
It has interchangeable lenses. The most popular lens is the 35mm f/2.5 which may be used on land, sea or air; in fact, this is a great camera for use in dirty, dusty and wet environments.
These are as I've measured or guessed.
Lenses: Interchangeable. The 35mm f/2.5 and 80mm f/4 lenses work in water and air. The 28mm f/3.5, 20mm f/2.8 and 15mm f/2.8 lenses only work under water.
Standard Lens: 35mm f/2.5 works on land, sea and air. 6-bladed manual diaphragm stops down to f/22. Focus from infinity to 2.75' (0.8m). Filter thread appears to be 58mm.
Filter Size (Standard 35mm lens): 58mm screw-in.
Focusing: Scale focus only. Guess or measure (tape) the distance and set it on the dial. There is no rangefinder. I'm unsure if the distances correspond to water or air.
Depth-of-Field Scale: Magic moving indicators move along the distance scale as you change the aperture.
Exposure Dial Settings: Aperture-preferred Auto (A), Mechanical 1/90 (M), Bulb (B) and (R) for rewind.
ASA/ISO Range: 25 - 1,600.
Shutter: 1/30 - 1/1,000 on Auto, I think. When tested it seems to be able to go for many seconds at night, an excellent plus. My Nikon FE of this same vintage could exposure perfectly for many minutes at night.
Flash Sync: Via a three-terminal connector under a screw-tight cover on the bottom plate.
Power: Thumb wind and rewind. Two S76 button cells for meter and shutter.
Power Switch: I can't see any. The finder LED goes out by itself.
Viewfinder Indications: One red LED explained under operation.
Weight: 34.125 oz. (967.5g), with film, batteries and strap lugs, no strap or case, measured.
HISTORY and NOMENCLATURE
The Nikonos (Calypso), Nikonos-II and Nikonos-III looked like traditional black rangefinder cameras and had slightly trapezoidal bodies. Their finders didn't pop out above the body as they do on the Nikonos IV-A and Nikonos V.
The -A of the Nikonos IV-A signifies new automatic exposure, and the large finder extends above the top plate of the camera.
The Nikonos V added TTL flash, orange or green outside rubber and shutter speeds indicated in the finder.
Lenses are interchangeable among the Nikonos, Nikonos II, Nikonos III, Nikonos IV-A and Nikonos V.
Nikon's only underwater SLR was the Nikonos RS of 1992 - 2001, which uses different lenses.
Easy: there are only four things to set: film speed, the shutter, focus and aperture.
Film speed is set on the left dial: lift and turn. Film loading is by flipping open the back and the pressure plate. Unlatch the back on the left by turning the O-C knob to O (Open).
The four shutter settings are around the wind lever on the right: A, M, B and R. Leave it on A, automatic. M is a mechanical 1/90 setting for when your batteries die or for flash. B is Bulb for long exposures (why?), and R is for rewinding the film.
To rewind, select R on the right dial, then lift and turn the rewind crank on the left side. Rewinding is clockwise as marked on the crank. Open the back, remove the film and then rotate the crank backwards (counter-clockwise) to push it back in.
Nikonos IV-A Focus and Diaphragm Controls
Set the focus distance by twisting the silver knob. Guess or use a tape measure. Depth-of-field is shown by the two red pointer which move as you set the aperture.
If you set the infinity mark to the red dot as shown above, you ought to have everything from the distance at the other red dot (6' or 1.8m in this example) in focus.
This distance scale is calibrated for air. If you use a tape underwater you'll need to correct it.
Set the aperture (diaphragm or f/stop) with the black knob.
Tap the shutter lightly and a red LED appears in the finder. If the red LED stays lit, exposure is correct and in the range of 1/1,000 to 1/30.
If the red LED blinks, exposure is over or under this range, so adjust the aperture until it becomes steady.
In dim light the exposure ought to be fine even if blinking, but the picture may be blurred from a long exposure. Hold steady or use a tripod.
I have no idea. I don't use this underwater. People who use underwater cameras love to brag about the expensive gear they flood. Get one tiny spec of grit on the O-ring and you're dead.
Thee is no bayonet lock to release, just a detent.
Twist the lens body 90 degrees until the silver knob is in front of the finder. Pull out the lens.
To replace a lens, put the silver knob in front of the finder and push in. Rotate 90 degrees until it's back as shown above.
I point the camera down so crud falls out, instead of into the focal plane shutter.
Underwater users pay close attention to the O-ring seals and grease. I don't know these procedures.
We'll see when I get the film back!
The shutter release is lovely: one smooth, long actuation releases the electronic shutter
This was a gift from Daniel in Sedona when he discovered that no one wanted this camera. Strange, but true. Today of course it only shoots film, but gosh, this is a sealed, waterproof, crap and crud-proof solid brick of a camera perfect for shooting anything that might shoot back or be messy. Try it in the surf!
Oddly the one I was given has some green corrosion on some of the chrome. What? This is an underwater camera - how on Earth does it corrode? It lives underwater! People tell me it corrodes when people forget to rinse it in fresh water after using it in salt water.
If you find this as helpful as a book you might have had to buy or a workshop you may have had to take, feel free to help me continue helping everyone.
Thanks for reading!
Caveat: The all the ads below come from third parties. I don't see them before they appear on your screen. See more at my Buying Advice page. Personally I get my goodies at Ritz (the store, not the hotel gift shop), Amazon and Adorama.