How to control the strength of a camera flash?

Discussion in 'The Projects Forum' started by lethalpossum, Nov 14, 2015.

  1. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Hello everyone,

    I have an instant camera that I really enjoy but I often find the flash too bright. So today I decided to open up the camera and see if there is anything I could do:

    IMG_20151111_224830_768x1024.jpg

    IMG_20151113_234209_768x1024.jpg

    I have some experience with electronics projects but I am by no mean an expert so please bare with me. I understand that the 380 µF / 320 V capacitor is what provides the short but high voltage electricity pulse which fires the flash bulb. What I am wondering is how I could control the intensity of that flash? I would like to be able to lower the flash intensity when taking a portrait but keep it to full strength for landscapes for example.

    My question is: would a potentiometer put before the flash bulb do the trick? A rotary potentiometer seems like it would be a very convenient way for me to adjust the flash intensity. But is there potentiometers rated for such high voltage? Ideally I would like to be able to reduce the flash all the way down because the camera as only two flash modes: always on and auto (based on a light sensor in the front). There is no off mode :(

    Thank you in advance for your advices.

    Regards,

    Tom
     
    Last edited: Nov 14, 2015
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Welcome to AAC!
    Unless you're trying for a Darwin Award, don't even think about messing with the flash. There is enough energy stored in that capacitor to KILL you :eek::eek:.
     
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  3. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Thanks for the advice Alec. I realize that this is a dangerous capacitor and I certainly don't want to take any chance. I am just wondering if there is a safe way to do what I want.
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    The files size that you attached were too too big, I were compressed them to the normal size, they are from about 3.8MB compressed to about 95KB, and another photo compressed from 4.3Mb to 101Kb, next time before you upload the files, please compress the photos to 800x600 or 640x480, if necessary then you can compress to 1024x768, almost the photos using 800x600 image is enough.

    Too much file size will affecting the connecting speed of members get to the forums, thanks for your understanding and cooperation.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    The capacitor is charged up from an oscillator, usually transistor and a small transformer and diodes, so you need to alter the output of the oscillator circuit, by putting resistors in series with the charger.

    You will probably get better help with photos of both sides of the pcb.
     
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  6. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Sorry about that! I thought that choosing the thumbnail option would avoid this issue. I apologize if that inconvenienced anyone and thank you Scott for fixing my mistake so fast.
     
  7. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Hi Dodgydave, the PCB is kind of attached to the camera body so I don't dare to take it apart by fear of breaking it. Here is a photo of the front of the PCB. Hopefully that will be sufficient. I also uploaded a larger image here: http://imgur.com/UxYe1Cj

    IMG_20151114_160247.jpg
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    You are way over thinking this and risking damaging your camera for no reason. Just tape a diffuser over the flash. Try different translucent materials to see what works best. Wax paper maybe for starters. You might even be able to find a commercial difffuser that snaps on your camera if you search.

    Or by an SLR with external flash then you will have tons of choices.
     
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  9. tindel

    Active Member

    Sep 16, 2012
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    As an added bonus you don't get D-E-D ded.

    If you have to ask about these things, you don't have enough experience to do these things!
     
  10. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Sounds like my M.O. :) I tried to block the flash light before with whatever I had at hand and just succeeded at casting weird shadows. Maybe I should just make a better feating DIY diffuser (there is no commercial ones for this camera). And that could also be the opportunity to play with color gels...

    BTW I have an SLR but I've really enjoyed instant cameras recently. But you get what you pay for (or less if you buy a Lomography camera or Impossible Project film, sorry for the rant).

    Anyway thanks everyone for your constructive inputs.
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Back in the day, my favorite defuser was 3M spray contact cement on an overhead transparency. You can go from fairly clear to really diffuse. Worked well for blurring our unwanted objects in the background while making prints as well. The transparency could be easily cut to any shape and the un coated side sat flat on the paper.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    A too bright flash on one of those seems unlikely!

    Some high end cameras have a chunky high voltage MOSFET to terminate the arc current - but I think that has more to do with eliminating red-eye.

    Reducing the voltage would probably make triggering unreliable, and quite tricky to remove a bunch of turns off the transformer secondary.

    That pretty much leaves reducing the capacitance value, but they're special photoflash capacitors - regular off the shelf electrolytics will probably have a short life.
     
  13. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    I think you are confusing intelligence with experience.

    Also, by your logic this forum would not exist.

    ak
     
  14. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    What???? Tindel's statement was spot on. Part of the purpose of this forum is to tell inexperienced members when they are venturing into a danger zone and it is not advisable to continue.
     
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  15. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes, part of learning a topic is learning how much there is yet to learn - put another way, how much you don't know.
     
  16. lethalpossum

    Thread Starter New Member

    Nov 14, 2015
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    Tindel's response was direct but I think I understand is point: I could be a kid in way over his head and about to get hurt. And he is probably right that as a newbie in electronics, I should probably revisit this idea when I have a few more projects with high voltages under my belt. But don't worry, I am a chronic hacker/tinkerer and it would take more than a comment to discourage me if it was not for safety reasons.

    Thank you all for caring about this great community.

    Cheers,

    Tom
     
  17. tindel

    Active Member

    Sep 16, 2012
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    Good attitude young man! Keep up the good work! There are plenty of low voltage things to tinker with that are safe, but teach you the basics that you need to know before venturing into high voltage applications. When you are ready to do the high voltage stuff, you'll know it. And you'll have the tools that will help provide you some level of safety.
     
  18. BReeves

    Member

    Nov 24, 2012
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    When I am faced with your situation, I just tape one or more layers of paper towel over the flash tube, toilet paper also works. The more layers the less light.

    The proper way to reduce flash intensity is to shorten the amount of time the flash tube is fired. This is what variable flash units do because you can't reduce the voltage on the flash tube and make it work. Doing this with your camera would be beyond complicated and simply not worth the effort.
     
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  19. DickCappels

    Moderator

    Aug 21, 2008
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    The amount of light should be nearly directly proportional to the capacitance. To get 1/4 the light change the capacitor from 320 uf to 82 uf (close standard value). Be sure to use a photoflash capacitor, otherwise the new one won't last long.

    By the way, it is a good idea to always short the leads of the capacitor before handling the circuit board of the capacitor itself.

    My method -put a piece of white printer paper over the flash's window. Cuts down the light and doesn't throw weird shadows. Half-tone patterns on a clear substrate should work quite well too (but haven't tried it).
     
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  20. Dodgydave

    Distinguished Member

    Jun 22, 2012
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