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Doubling capacitors in flash?

Discussion in 'General Electronics Discussion' started by nebojsa, Jul 18, 2017.

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  1. nebojsa

    nebojsa

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    May 13, 2017
    Hello...
    I have a flash with circuit in atachment.
    Can I add one more capacitor (800uF 330V) in parallel with C3 (500uF 330V) without
    Inconvenience?
    If not is there any way to replace some otner parts of the flash to make it work safe with doubled capacitors?
     

    Attached Files:

    Last edited: Jul 18, 2017
  2. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    What's your goal here? A longer, or a brighter flash?
     
  3. nebojsa

    nebojsa

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    May 13, 2017
    As far as I know - longer. But, what I dont know is it safe for rest of circuit.
     
  4. BobK

    BobK

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    Jan 5, 2010
    It might overdrive the flash tube and destroy it. Even if it doesn't right away, it would likely shorten its life.

    Bob
     
  5. nebojsa

    nebojsa

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    May 13, 2017
    I agree. Any other part of circuit?
     
  6. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    If you can find the data sheet for the bulb that's how we'll know. You can look up replacement bulbs for it, or take the bulb out and look for part numbers. The data sheet is really how we'll know. Also, why do you want a longer flash. (Just covering all bases) I assume because you want to open your shutter a little longer to have a brighter scene. Maybe there's another way to get more light?
     
  7. davenn

    davenn Moderator

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    so you do a longer exposure time ... same effect

    what are you trying to photo that you think a longer flash time is needed ?
     
  8. nebojsa

    nebojsa

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    May 13, 2017
    I want to use it on my camera with up to 1/100 sec exposure. Flash duration (acording to some sources on net) is a few miliseconds or less. I think that even doubled power will fit in this 1/100 part of a second.
     
  9. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    My two cents is that flash is fairly cheap. So go for it if it explodes, saftey squints. There are a lot of variables here. We'd have to know the trace size and part numbers of all components between the capacitors and flash. Just remember capacitors are like vindictive girlfriends they'll shock you when you least expect it. So, discharge them before messing around.
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    that needs clarifying

    most decent cameras will sync happily up to 250th of a sec with a flash
    do you have a low quality camera ?

    you don't seem to understand some of the basics of photography

    you do also realise that each full aperture stop you open up is double the light ?
    or as I said earlier you can decrease the shutter speed one stop and double the amount of light
    or for a 3rd way, you can increase the ISO setting eg going from 100 to 200 or say 200 to 400
    also double the amount of light

    so there isn't really any need to mess with your flash unit


    so again ... what are you trying to photo ?
     
    Last edited: Jul 18, 2017
  11. BobK

    BobK

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    Jan 5, 2010
    Twice the light = 1 stop higher = better depth of field.

    Bob
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    actually DOF shortens as you open the aperture ;)

    f2.8 has less DOF but twice as much light than f5.6
    (as I was saying in my previous post)

    I, as with most togs, like doing portraiture with open aperture for that very reason

    an example I recently posted on another forum ..... f2.8 f/l 88mm
    it's a great method for separating the main object from the background

    [​IMG]



    Dave
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It is generally shorter exposures which are a problem when using a flash.

    Assuming you're using a film with a focal plane shutter, the limit is the fastest speed at which the second curtain is released after the first curtain has fully opened.

    A focal plane shutter works by having one (first) shutter which uncovers the film or sensor and another (second) shutter which covers it back up again.

    At slow shutter speed (longer exposures) the first curtain opens, then the second curtain closes.

    At fast shutter speed (shorter exposures) the second curtain is released while the first curtain still partially obscures the film/sensor. At very fast shutter speeds, the difference between the two shutters if very small, leading to a thin open slit moving across the film/sensor.

    The fastest speed at which the entire film/sensor area is exposed all at once is the sync speed of the camera. This is the fastest shutter speed at which you can use a conventional flash.

    Perversely, at faster shutter speeds, the flash duration needs to be longer.

    For a typical flash, the peak intensity is a couple of ms. This is fine for any shutter speed from the sync speed and longer.

    The sync speed is very close to the time it takes for a single curtain to traverse the focal plane aperture. Incidentally, it is also close to the actual time all exposures shorter than this take. As an example, a camera with a 1/90sec sync speed takes about 1/90sec to take a 1/1000sec exposure!

    Because of this, shorter exposures require a longer flash duration (and also a very even level of illumination). With a 1/90sec sync speed, the flash needs to stay on for at least 12ms for a 1/1000sec exposure. Some modern flashes do this by pulsing the flash very quickly.

    Even if you do this, then for the same flash power spread out over 10 times the duration with only 10% of the aperture open at any time, you only get 1/10th (not 1/100th) of the exposure.

    A better solution to needing a faster shutter speed with a flash is to stop down or use a neutral density filter. Assuming the majority of the exposure comes from the flash, the flash itself determines the duration of the main exposure, not the shutter speed. You only need a shutter speed at or below the sync speed.

    If you don't want to stop down (because you want a shallow depth of field) then the simple solution is to use a slower film speed (lower ISO) or an ND filter. Naturally, you may also need to make corresponding changes to flash power.
     
    Last edited: Jul 19, 2017
    hevans1944 and davenn like this.
  14. nebojsa

    nebojsa

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    May 13, 2017
    I want to do something like this guy did in this link.
    http://desmond-downs.blogspot.rs/2010/09/turbo-flash.html
    A lot of images are not available in link above. On google search can be found first 7 images.
    https://www.google.rs/search?q=Turb...E5oKHRObBhoQ_AUIBigB&biw=1440&bih=728#imgrc=_
     
    Last edited: Jul 19, 2017
  15. nebojsa

    nebojsa

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    May 13, 2017
    My camera can sync up to 1/250 s, but I rarely use faster than 1/100s.
    Here is the link. This guy did it with realy tiny flash.
    http://desmond-downs.blogspot.rs/2010/09/turbo-flash.html
    A lot of images are not available in link above. On google search can be found first 7 images.
    https://www.google.rs/search?q=Turb...E5oKHRObBhoQ_AUIBigB&biw=1440&bih=728#imgrc=_
     
    Last edited: Jul 19, 2017
  16. nebojsa

    nebojsa

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    May 13, 2017
    No, I dont have low quality camera. And my camera can sync up to 1/250s, but I dont use faster than 1/100s.
    And maybe I want to stop down aperture to lengthen depth of field.
    Or I want to overpower the sun with flash like in this photo
    http://farm3.static.flickr.com/2477/3798479224_eec22f2deb_o.jpg
     
    Last edited: Jul 19, 2017
  17. nebojsa

    nebojsa

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    May 13, 2017
    Ok. I take caution when working with big capacitors. I will try first with lower combination of capacitors ( I have three 500uF, 800uF and 1000uF) and take test shots with diferent speed and aperture for comparasion. In the end I will atach all of them to test.
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    So what do you actually want to do? And I don't mean adding capacitors, I mean what sort of photography are you currently unable to do that you think adding capacitors to your flash is the answer.
     
  19. nebojsa

    nebojsa

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    May 13, 2017
    Flash (or flashes) for overpowering the sun photography.
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    What do you mean by "overpowering the sun"?
     
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