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SB24 High speed flash conversion [tutorial]

Discussion in 'General flash photography, lighting, and technique' started by Desmond, Sep 12, 2008.

  1. Edit : This is only applicable to the D40 , D50 and D70/S since they use an electronic shutter for higher speeds rather than a focal plane shutter as other camertas do .
    Update : see my realsncyh blog
    A few people have expressed interest in high speed flash synch so I thought I'd take a few pictures of my newly acquired SB24 being 'converted' . [edit: you can do this with any of the older Nikon flashes that have "A" mode - or just use a flash with one pin ]
    The 'easy' method is to slide a piece of paper under the back two pins to disconnect them from the camera . NOTE : this only works with the D70 , D40 and D50 [ and maybe the D100 ] since they have a mechanical shutter plus an electronically switched shutter that allows flash synch at any speed limited only by the firing time of the flash .
    Here's a picture of the bottom of the flash and the associated pins ....

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    the two bottom pins are the ones to disconnect , one of them tells the camera there is a flash connected and ready to fire - we don't want that because then the camera defaults to flash speeds , maybe 1/60th to a max of 1/500th [ the new D90 can only do up to 1/200th !] .
    The other pin is useless because the SB24 doesn't speak the same language as i-ttl on the newer cameras .
    The top pin could also be disconnected but comes in useful if you have the flash set to 'standby ' mode because this pin tells the flash when the camera has been turned on and wakes the flash up !
    Last edited by a moderator: Jun 13, 2009
  2. 4 screws at the base of the flash allow it to open like this ... there are no dangerous voltages here but leave the batteries out to be safe .

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    Cut the gray and green wires off and throw them away ....

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    Now you have a flash that works at any speed on the cameras mentioned BUT , you must enter the values manually [ iso , aperture and zoom ]
    test results to follow ....
  3. No flash iso 200 , F5.6 1/8th ....

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    plus flash for ballanced ambient for normal use ....

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    But when you go outdoors into bright sun and want to overpower the harsh light speeds need to go higher , at 1/1000th the picture would be totally black in my indoor example but the SB24 has synched in 'A' mode ....

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    How many flashes can synch at 1/2000th ?

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    1/4000th ???

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    at 1/8000th I've cut the flash in half but it still synched to a degree .

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    Newer cameras have fp high speed but that spreads the flash out and cuts a slice of it drastically reducing the power .
    The SB24 fires at 1/1000th at full power which means that 1/1000th is just about safe at full power .
    1/1100th at 1/2 , 1/2700th at 1/4 which mean a safe 1/2000th shutter speed at 1/4 power . 1/5500th at 1/8th power , a safe 1/4000th shutter synch speed , 1/11000th at 1/16th output which should give a safe 1/8000th synch speed .
  4. Not much response so hopefully someone is benefitting from this info - I'm learning a bit as I do the tests so I'll keep going ....
    Today I took some test shots in bright sunlight .....

    These are not necessarily pictures people would want to take but there are many that would love to be able to have fill flash at F2.8 in sunlit conditions and these are the speeds people would need the flash to synch at .

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  5. A more 'human' subject ... distance 4 meters

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  6. Some good info ! I don't have a SB-24 , but those that have one , it's something to think about. I tryed the high speed sync. last week for the first time using the SB-800 and D300 , and was very happy with the results , but your flash range is very limited . But it does work well . Here is an example shot at 1/2000 / f2.8 / 85mm with the SB-800
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  7. Nice picture , thanks for contributing to the discussion . next sunny day I have some time want to do a direct comparison between fp and proper high speed synch .
  8. jhpate


    Jul 14, 2007
    texarkana, texas

    thank you for taking the time to do this post. I appreciate it. :) 
  9. Thanks for letting me know :smile: For a while it didn't look like many cared much about it but I'll just keep waffling and posting my results so I have something to refer people to when they ask relavent questions ...
  10. spoot


    Aug 29, 2007
    Great info, thanks Desmond. Not that I have a sb-24, but still good to know :D 
  11. Hope you get to try it one day ! It doesn't have to be an SB24 , many of the older flashes will do the same job , and you don't even have to disconnect the wires - simply sliding a piece of paper under the back two pins will do the same thing - an SB800 on 1/128th power will give speeds of 1/41600th sec .
    This shot was taken at 2 seconds in the dark with an SB800 triggered by the starter solenoid that broke the bulb , two wires connected to the back contacts of the solenoid fired the flash as it connected the bulb with a bolt ...
    the flash was set to manual 1/128th and fired at 1/41600 th of a second .

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    The setup ...

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  12. Desmond.......You are the McGiver of Nikon Cafe!

    I appreciate all your effort sharing this information with all of us.

    God Bless America,

    P.S. My ex-brother in law lives in New Zealand. He just opened a microbrewery and restaurant there. Said it's really slow due to the bad economy. Not sure where he lives in New Zealand, but I'll find out.
  13. Maybe he lives close to me :smile:
    I meant to add these samples from my first real test drive with the setup , the 70-200VR was on my D40 at this wedding last Saturday . For the first time I went manual and exposed to darken the background a bit , iso 200 , F4 and 1/4000th of a second and the flash was actually still a bit too strong . The SB24 was set at iso 200 F2.8 'A' mode .

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    Then I backed away a bit and set the flash zoom to 24 mm to waste a bit of light and back off the flash a bit at F2.8 and 1/800th ....

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  14. very clever, might pull apart my SB26 and do something similar

    Nice post Desmond - thanks
  15. "Plan B" is to just slide a piece of paper under the back two contacts , otherwise fit the flash and see if it limits you to 1/500th or not , you may not need to disconnect anything .
  16. WayneF


    Apr 3, 2006
    And of course, the two second shutter speed does not need the two wires broken at all. The flash at 1/128 power is what provides the speed, assuming insignificant ambient room light to interfere.

    Also just using a regular PC sync cable also breaks the two pins, breaking communication with the camera.

    Seems good to repeat as often as possible, the very fast shutter speeds with flash are only possible on the electronic shutters like D40, D50, D70, etc.
  17. mariusz


    May 23, 2006
    Houston, TX
    Great info - thank you. Makes me want to get SB24 since I use flash a lot outdoors.
  18. WayneF


    Apr 3, 2006

    ?? Dont understand. I fear some bigger picture facts are being overlooked. Your sig says SB-900 and SB-600s. Why would you need a SB-24? The SB-24 was a good ole flash, but the SB-900 will do absolutely anything the SB-24 will do (and much more - except for backwards compatibility with old film cameras).

    And your D300 has a focal plane shutter, which is never fully open above the 1/250 second sync speed. Flash simply will not work the same there as the D40/D50/D70 discussed. So this is going to be absolutely impossible. I am not getting the point? :) 

    Your D300 and SB-900 already provides the FP HighSpeed Sync option, where you can set any faster shutter speed with flash, like 1/2000 second. This very special mode converts the flash to be a continuous light so it keeps firing as the FP shutter moves its narrow slit. This is only high speed sync however, it is the opposite of high speed flash. It drastically reduces the available flash power.

    Assuming a D40/D50/D70 shutter, perhaps you meant the SB-24 as an inexpensive substitute, expendable, to preform surgery on it. But it is not necessary to expend anything, just use a PC sync cable instead on your SB-900. This is not hot shoe mounted but it works the same - surely better if off camera. If it must be hot shoe, you could add a cheap hot shoe adapter that provides both PC Sync connector, with a cold shoe on top of it. This also breaks the two pins.

    Any non-Nikon speedlight flash (cheap Vivitar, etc, but a hotshoe flash as opposed to studio lights) is very fast at low power levels (and does not have the two pin communication). Some models only go down to 1/16 power, but that is still pretty fast. All you need is a way to trigger it. SB-900 has PC sync connection and an optical slave trigger too, and it is definitely the big boy here, extremely versatile. The SB-600 has a Manual mode, but it does not have a PC sync connector, but you can add one via a third party flash foot adapter.

    The speedlight flash duration is generally much faster than any shutter speed, so the way to capture fast action is NOT shutter speed. Shutter speed is the hardest way. The great way is to be in a halfway dim place (any normal room, not in sunlight) where the continuous ambient light is not much factor. It does not need to be very dim. For small things, lamps breaking or milk drop splashes, the flash can be only a foot or so (at very low power for speed), and therefore you can easily use f/16 for depth of field at maximum shutter sync speed, say 1/200 second. 1/200 at f/16 makes any room ambient be dim and out of the picture. Meanwhile the very fast flash at low power stops very fast motion, faster and better than any shutter can do it.

    See THIS LINK about the speed of speedlights, and about how shutter speed simply does not matter to the flash duration. Low flash power in speedlights is what stops action, so long as bright ambient does not overcome it.

    Outdoors in brighter light is the only place you need a faster shutter speed for motion, because that brighter ambient is hard to ignore and it will blur fast action. This faster shutter speed does greatly limit the light from the flash, but at least the bright ambient does not blur the motion. Then, for that, you could use the paper or tape to disable the two flash pins in the shoe, or could dismantle the flash to disable them, or you could simply use a PC sync cable, which also disables the communication between flash and camera. Or use the hot shoe adapter which provides a cold shoe above it. Any of these methods results in Manual mode flash, and any prevents the camera from realizing there is a flash in play.
  19. mariusz


    May 23, 2006
    Houston, TX

    I wasn't aware that I can drive my SB900 anywhere below 1/320s. What settings should I change? BTW you are right about me performing surgery on $50 flash than on $500 one.
    You have a wealth on information on your website, thank you for excellent explanation too.
  20. WayneF


    Apr 3, 2006
    Below 1/320? I am sorry, I am not understanding. The question seems very unusual. I hope you can add more words of description. Maybe the word drive is confusing me. Or maybe you meant "above 1/320" ?

    I should ask first, but my advice would be, first of all, get it out of FP sync mode. It has too much power cost if you exceed maximum sync speed by accident, and FP seems totally unnecessary and unproductive in any but the one special situation of fill flash in bright sun at moderately close distances. Possibly that is exactly what you want to do, but you will really know exactly when you need it, and any other regular flash is NOT that situation.

    Just set regular 1/250 sync (without any FP in menu, a line or two down).

    Then simply set your camera shutter speed to any speed 1/250 second or below. Same as for any regular flash, which it is (fancy, but regular). The flash will have it full power capability then, and will be faster than lightning regarding stopping motion.

    A fast shutter speed choice like 1/250 second will keep out most of any normal ambient light indoors at night. Slow like 1/160 second will allow more of it in, for ambience. Camera modes like A and P are (usually) going to set 1/60 second anyway, but you can set shutter speed anyway you wish in camera M mode.

    Or assuming you meant "above 1/320", then yes, the 1/320 PF flash mode allows it. Why would you want to? I think you need to know the exact right answer to that first. :)  And you need to know the cost of it. Should we pursue this route?
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