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Thread: Building a universal flashbulb gun

  1. #1

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    Building a universal flashbulb gun

    Hi All,

    I've recently dug into flash bulbs. I'd like to begin experimenting in the studio. I have never done any kind of artificial lighting before aside from flashes built into cameras that go off when I don't want them to.

    I have a Tilt-A-Mite flash gun on the way, but I'm sure it will only hold the small bulbs.

    I also have an old HP D/C adjustable power supply.

    Is it possible to look up the trigger voltages for flashbulbs of various types, dial in my power supply, connect the red probe to the lower bulb contact, and the black probe to the screw contact, and pop away? Either by turning on the PSU, or using alligator clips to connect the positive wire to trigger the bulb?

    Could it be that easy? (If I don't want sync) All I'm doing is getting the ignition filament hot enough so it sets off the more intense light emitting filaments, right?

    If I DO want sync, could it be as easy as flaying open a PC cord, and connecting my alligator clips from my DC source to the right wires? If I understand correctly the leaves of the shutter are wired with contacts that briefly kiss during the exposure, completing the circuit and allowing electrons to flow, so I could leave the power supply on during the whole operation and get a synced exposure only when I trigger the shutter.

    I have a Fujinon 150 5.6 W that has a flash port but no mention of it's class. No "M", "X" or anything that I can see, aside from "B." Do unmarked flash sockets usually mean one or the other?

    I did do a search before posting, and found information on the forum here and here. There is some talk of using a solenoid and capacitors to build a sync flash gun of sorts, but is that really necessary?

    Thanks,

    Sylvester

  2. #2

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    Re: Building a universal flashbulb gun

    Your lens is X sync all it needs is a flash plugged into the PC socket on the lens. The batteries in the flash will fire the bulb. But since you have X sync the bulb will ignite immediatley. You need M sync for your shutter to fire properly timed flash bulbs.

  3. #3

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    Re: Building a universal flashbulb gun

    M synch pre-fires the bulb by about 20/1000 of a second because it takes a while for the stuff inside the bulb to get burning, so you need to start the bulb before the shutter opens. But you can use X at 1/25 second or so and below. Leaving the shutter open longer takes the shutter-open time into the full-ignition period of the bulb, which probably would work in most cases indoors.

    And, yes, your basic scenario would work, but easier is to buy an old Graflex flash handle that takes all sizes of bulbs with adapters, has fittings for cords, and a hole in the bottom for a light stand mount. The Tilt-a-mite will take #5/25 and M2/3 bulbs, though, which is probably all you need.

    There's no need for a power supply and being tied to the wall. Three D cells will fire any bulb, and last just about forever in this type of application. They also won't fry your shutter if you make a mistake.

  4. #4
    Jac@stafford.net's Avatar
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    Re: Building a universal flashbulb gun

    Michael Darton's information is right on. (Dunno about the 'mite using #5 bubs, but it's a minor point. Randy Moe is another flashbulb enthusiast and can probably tell us.)

    Flashbulbs require only 3 volts to fire, and the Graflex type (there are other brand equivalents) is excellent in every regard. It has good power capacity, can trigger almost every kind of bulb (except flash cubes which the improved 'mite did accommodate) and is expandable to fire external units via cords and via optical slave. The reason early flash units used 15 to 22 volt batteries (and a capacitor) was due to the poor durability of early dry batteries. Those days are over.

    The 'mite has an 'open' flash button to fire the flash directly - you open the shutter using B, press the 'open' button to flash, then close the shutter. However, as Michael noted 1/25th of a second or slower with a cord works just fine.

    Another point that has been established is that one can use a flash meter with bulbs if the meter has a cord/PC connection. Of course, that uses up the bulb for reading and the bulb must be replaced for the actual taking.

    Finally, if you really get into bulb flash there were batteryless units. Yes, no battery required because they used a built-in magneto, but that's getting off track here. (Flashcubes required no battery but they were puny and expensive.)

  5. #5

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    Re: Building a universal flashbulb gun

    The tilt-o-mite has an ingenious socket that automatically adapts to several different sized bulbs. I know it takes AG and #3s and I think it will take #5s too. It is about as close to universal as you're going to find. The capacitor is probably still good, I used a garage door opener battery to fire it, just a little bit of metal to fill in the gap and it works fine.

  6. #6

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    Re: Building a universal flashbulb gun

    Quote Originally Posted by mdarnton View Post
    And, yes, your basic scenario would work, but easier is to buy an old Graflex flash handle that takes all sizes of bulbs with adapters, has fittings for cords, and a hole in the bottom for a light stand mount. The Tilt-a-mite will take #5/25 and M2/3 bulbs, though, which is probably all you need.

    There's no need for a power supply and being tied to the wall. Three D cells will fire any bulb, and last just about forever in this type of application. They also won't fry your shutter if you make a mistake.
    Thank you for the replies, all.

    It seems that graflex holders are in short and expensive supply right now. I guess because you can use them to make lightsabers? (???)

    And I don't know, setting my power supply for 3.1 volts, and connecting the alligator clips to the two lead wires of the PC cord sounds pretty easy to me!

    Of course, I guess the shutter would only start to open after the bulb has ignited with my modern lens, so I would lose some lumens.

    There is a little screw next to the flash socket on my lens. I'm assuming this is just a service or replacement terminal, but any chance I can tune the synchronization of the mechanism via this screw?

    Click image for larger version. 

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    -S

  7. #7

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    Re: Building a universal flashbulb gun

    Quote Originally Posted by Sylvester Graham View Post
    Thank you for the replies, all.

    It seems that graflex holders are in short and expensive supply right now. I guess because you can use them to make lightsabers? (???)

    And I don't know, setting my power supply for 3.1 volts, and connecting the alligator clips to the two lead wires of the PC cord sounds pretty easy to me!

    Of course, I guess the shutter would only start to open after the bulb has ignited with my modern lens, so I would lose some lumens.

    There is a little screw next to the flash socket on my lens. I'm assuming this is just a service or replacement terminal, but any chance I can tune the synchronization of the mechanism via this screw?

    Click image for larger version. 

Name:	IMG_7957.jpg 
Views:	13 
Size:	51.3 KB 
ID:	144475

    -S
    Your shutter has no sync time adjustment. It fires the flash as soon as the blades are fully open. Why not just use an electronic flash? That way you will have proper sync at all shutter speeds and not have the expense of hard to find bulbs? You also will eliminate the old time photographers thrill of having bulbs go off accidentally in your pocket, your hands or just exploding and shattering? Plus, try to find press 5 or 25 or AG 1 bulbs on a Friday night before you need them.

  8. #8
    Jac@stafford.net's Avatar
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    Re: Building a universal flashbulb gun

    Quote Originally Posted by Sylvester Graham View Post
    It seems that graflex holders are in short and expensive supply right now. I guess because you can use them to make lightsabers? (???)
    If you think $60 is expensive, then shop for flashbulbs. You might just faint. (There are other flashes other than Graflex such as Heiland.)

    Of course, I guess the shutter would only start to open after the bulb has ignited with my modern lens, so I would lose some lumens.

    There is a little screw next to the flash socket on my lens. I'm assuming this is just a service or replacement terminal, but any chance I can tune the synchronization of the mechanism via this screw?
    That screw just holds a piece that covers some workings.

    No light lost. The X flash begins only when the shutter is fully open. A synchronized bulb flash shutter usually ignites the bulb 20ms before the shutter opens in order to let the flash begin its burn. Bulbs are slow.

    Some shutters had adjustable flash delays with delays of 23ms, 20ms, 5ms and 0. One such shutter is the No 3 Acme Synchro. Some others used a solenoid to trigger the shutter; the delay was set via the solenoid.

  9. #9
    Steve Smith's Avatar
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    Re: Building a universal flashbulb gun

    Most bulb flash units consisted of a battery, a resistor, a capacitor and the flash bulb all in series in a loop. Pushing in the flashbulb completed the circuit and started charging the capacitor. The resistor limits the current so the bulb does not fire immediately.
    The camera sync contacts are connected so that when they close, the capacitor discharges into the bulb and fires it.
    A capacitor is used because it has a lower internal resistance than a battery and will fire the bulb with more consistency than just the battery.


    Steve.

  10. #10

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    Re: Building a universal flashbulb gun

    Quote Originally Posted by Steve Smith View Post
    The resistor limits the current so the bulb does not fire immediately.
    Steve.
    I am no engineer, but... so we've got a circuit with a battery on one end. Somewhere between the batter and bulb in that circuit is a resistor followed by a capacitor?

    Is the resistor there to actually delay the current? Or does it smooth out the slope of the current peak so that the filament reaches ignition voltage gradually instead of suddenly?

    Quote Originally Posted by Steve Smith View Post
    A capacitor is used because it has a lower internal resistance than a battery and will fire the bulb with more consistency than just the battery.
    I'm figuring a scientific voltage source will be very consistent, better than those old dry cells anyways.

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