Nikon BC-7

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Nikon BC-7  flash for bulbs

 

One of the two original dedicated flash designed for the Nikon F (Another being the Nikon handle-mount Speedlight Unit). Compact and cordless flash unit which fits directly onto the Nikon F. A standard 15V battery is used. Synchronizing cord terminal is fitted to facilitate the use of an extension flash. The reflector is a collapsible fan type. Click-stop swivel head permits direct or bounced light. It is provided with a three-way socket permitting use of bayonet, miniature base or AG-1 flash bulbs. Test circuits incorporated allow check of the bulb, capacitor charge and synchronizing circuit. On the front of the flash, you can see the reflector, the three-way bulb socket in its center, and the F/F2-type foot. When the reflector is folded, you can see the test button. The left side has the two-socket (non-PC) sync connector, while the right side has a small white charge tester button. The silver button on top of the unit is the bulb ejector. On the back, from top to bottom, are the test lamp, exposure calculator-disc, and the rear-cover clip. The reflector may be rotated through an angle of 135 degrees, from directly pointed at the soon-to-be-blinded subject to nearly facing the wall behind you.   

The first step should be to insert the battery, which is a 15V dry cell, Mallory 504 or equivalent (Duracell 504, Radio Shack Unlimited #RSU10048510, or Varta V74PX, which is alkaline and not recommended). Slide the rear-cover clip down and remove the cover (which holds the exposure-disc); the positive terminal should be aligned towards the top of the unit. Then mount the unit on the camera.

Before loading any film, wind the advance lever and hold in the (front-mounted) test button for a few seconds. When you release the shutter, the test lamp should light up to indicate that everything is working properly.

 Now you can deploy the reflector by hooking it into one of the two slots. The "nearer" slot (shallow bowl) illuminates approximately a 35mm lens's field-of-view, while the "farther" slot (deeper bowl) illuminates about a 45mm lens's FOV. Of course, you can leave the reflector furled and use bare-bulb flash at a fraction of the cost of a new Sunpak 120J (on the other hand, the Sunpak offers 3 auto-apertures, manual power attenuation, and on one model, TTL flash control).

The three-way bulb socket will accept bulbs of the S.C. bayonet-base, minature base (M2, M3, etc.), and all-glass (AG-1) types. When you insert a bulb, the BC-7 begins to charge its capacitor; full charge is reached when the test lamp glows after pressing the white charge test button. Note that bulbs are either clear or blue-coated: clear bulbs are suitable for black and white film, because their light output is very warm, while blue-coated bulbs approximate the sun's light output temperature (appox. 5800K). Blue-coated bulbs are designated by a "B" at the end of their name. The flashbulbs recommended by J.D. Cooper in his Nikon-Nikkormat Handbook are the FP 6, FP 26, M3, and AG-1 (preferred in that order, because of their sync speeds).

Basically, appropriate sync speeds are determined by the type of bulb in use (different types have differing flash durations); in general, type FP bulbs should sync at all shutter speeds. I have a table that explains this more clearly on either the F Questions or the F2 Questions pages, depending on your camera.

Determining exposure is relatively simple. You line up the shutter speed in use with the ASA film speed in use (use the black scale for black-and-white film with clear bulbs, or the red scale with blue-coated bulbs) and determine your aperture based on the shooting distance. For shutter speeds slower than 1/30, you can use the guide-number to determine exposure.

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