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Thread: Open Bulb Flash technique questions

  1. #21

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    Re: Open Bulb Flash technique questions

    Need a high speed camera...

    How about a slow camera and a fast measurement?

    Make a cardboard disk (black with a white radial stripe) and spin it in a variable-speed drill. Photograph with your 60 fps video while you fire the bulb. The width of the blur will give you the flash duration in fractions of a rotation period, and the video will tell you what that period is.

    Ignition delay may be more important than duration, but if you fire a strobe simultaneously with the bulb, you may be able to get a good estimate of that, too.

  2. #22
    Tin Can's Avatar
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    Re: Open Bulb Flash technique questions

    Quote Originally Posted by Harold_4074 View Post
    Need a high speed camera...

    How about a slow camera and a fast measurement?

    Make a cardboard disk (black with a white radial stripe) and spin it in a variable-speed drill. Photograph with your 60 fps video while you fire the bulb. The width of the blur will give you the flash duration in fractions of a rotation period, and the video will tell you what that period is.

    Ignition delay may be more important than duration, but if you fire a strobe simultaneously with the bulb, you may be able to get a good estimate of that, too.
    Great ideas. I like them both and will try them.

    Thanks.
    2022

  3. #23
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    Re: Open Bulb Flash technique questions

    Her's a separate question, that this thread may be able to handle.

    I want to fire an electronic flash, Nikon SB800 in a random sequence for 2 hours with a known flash total count without a camera connected.

    Any cheap simple ideas?

    It's retinal memory project.

    and LF open bulb image.

    This is a cool idea, but may not do what I want. I placed an order however it ships late for my project.


    I may be able to make it work with a relay to buffer the electronics.
    2022

  4. #24

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    Re: Open Bulb Flash technique questions

    If you speak even pidgin digital, you can breadboard a linear-feedback shift register for practically nothing. Use a 555 timer for the clock, and either 7474 flipflops or a multiple-FF package for the register. The minimum interval would be one clock period, and the maximum would be determined by the length of the register; for photography, you might want to bound the minimum interval by using a second 555 and gating out pulses which fall within its period. Finally, a one-shot at the output will give you trigger pulses that are short in comparison to clock period.

    The poor man's solution to noise immunity (important if there is a lot at stake) is to put the circuit inside a metal box, running off of battery power, and bring out only the normally-open contacts of a small relay.

    You could also do this with industrial time delay relays, which would be fun to watch but pretty expensive.

  5. #25
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    Re: Open Bulb Flash technique questions

    I have been studying the 555's. Some of the usual socket based industrial timers are pretty cheap now, I have used those many times, but never paid the price 20 years ago as they were $100s, now offshore is not.

    Last night I gave up on random, as I found it not necessary for my secret project.

    My Nikon P7000 will fire an external flash every 30 seconds which works for me.

    I will try the cheap intervalometer to streamline my system when it gets here.
    2022

  6. #26

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    Re: Open Bulb Flash technique questions

    Quote Originally Posted by Randy Moe View Post
    Yes, Jac, I have read that one bulb will fire another (secondary ignition) and a whole bag, pocket or box can make some excitement and danger.
    met an oldtimer at a camera swap meet once who's hand was all messed up - seems he was reaching into a box of loose flashbulbs and static electricity set one off - setting them all off

  7. #27
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    Re: Open Bulb Flash technique questions

    Quote Originally Posted by DrTang View Post
    met an oldtimer at a camera swap meet once who's hand was all messed up - seems he was reaching into a box of loose flashbulbs and static electricity set one off - setting them all off
    I fell off a perfectly fine motorcycle and hurt myself.

    I still ride and have for 50 years.
    2022

  8. #28
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    Re: Open Bulb Flash technique questions

    Quote Originally Posted by Randy Moe View Post
    I want to fire an electronic flash, Nikon SB800 in a random sequence for 2 hours with a known flash total count without a camera connected.
    What do you mean by a random sequence? Do you mean a device will choose to fire the flash on its own with random intervals? I do not know of any.

    The SB800 has two flash synch terminals and one is intended for non TTL use. Can you use a terminal adapter and an ordinary, inexpensive intervalometer to fire it?

  9. #29
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    Re: Open Bulb Flash technique questions

    Quote Originally Posted by Jac@stafford.net View Post
    What do you mean by a random sequence? Do you mean a device will choose to fire the flash on its own with random intervals? I do not know of any.

    The SB800 has two flash synch terminals and one is intended for non TTL use. Can you use a terminal adapter and an ordinary, inexpensive intervalometer to fire it?
    #1 Yes, but I have moved on to sequential after last night's experiments. I can calculate total flash power easier when using many instances.

    #2 That is why I am waiting for the Canon Intervalometer I linked to, Canon because it has a 3 wire interface, but it's designed to fire a camera and not a strobe. Einstein or SB800 may have a higher shorting current than a camera. I will not be using flash bulbs for this.

    I try not to break things...
    2022

  10. #30
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    Re: Open Bulb Flash technique questions

    I didn't buy the cheap Canon Intervalometer, I bought the cheap Nikon version as it can do 2 things for me. One it works as advertised with my D7000. Not a waste of $15. This one on eBay.

    Most importantly it can time and fire Nikon SB28 repeatedly in sequence. It may work with any modern strobe, but I am not testing it further.

    One practical usage is paint by light with strobe, using open bulb shutter at night. Very applicable to LF shooting or any format.

    I was worried the SB28 may blow the circuitry on the timer, but I just ran it for an hour every 10 seconds. I used SB28 as it has paid it's way for 18 years. Almost expendable.

    Since timer has a stereo mini phono I plugged a PC to mini mono phono plug in and bingo it works perfectly. No tinker needed. Plug and Play.

    My plan for this combo uses a 32" silver umbrella with GoBo, which when viewed at night at a distance will create retinal images, which are fleeting mind/eye photographs, organically imprinted, not digital and not based in physical materials as we commonly think of photography. It will produce an ULF image, 32". Impossible to show in any way except by high speed video. Yet humans perceive it easily.

    I think this will puzzle, enthrall young at heart, anger others, when it debuts in a month.

    Maybe it already angers some here, as not photography, but I maintain it is imaging, hence it is photography.

    I'll update the actual imaging results and viewing reaction in a month with explanation of delivery and purpose. Secret until tactique du fait accompli. French says it better, but I don't know French...







    That's my story and I'm sticking to it.
    2022

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