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Thread: How to use SB-400 in manual mode?

  1. #21

    Default Re: How to use SB-400 in manual mode?

    Think about it for awhile ...

    It's not complex.

    What could possibly affect light output from a flash unit in such a manner that using -1EV may not be equal to toggling light output/power when going to manual mode?

  2. #22
    Senior Member B-setting's Avatar
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    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by ZerocoolAstra View Post
    do explain please!
    0EV to -1.0EV is a reduction of 1 stop of light.

    1/8 power to 1/16 power is also a reduction of 1 stop of light.
    i am only speculating.

    there might not be a linear relationship between EV adjustment and flash output. Afterall, EV adjustment tweaks the ability of the sensor to receive reflected light from an object.

    flash output adjustment directly modifies the amount of light going from the flash to the object. whatever light reflected back from the object and travelled into the camera sensor is mainly affected by the reflectivity of that object, for example, look at the difference between objects like a white dress against a black dress.

    so, why not do it the easier way if you want to play with light control, i.e. tilt, bounce or diffuse the flash.

    Last edited by B-setting; 14th January 2010 at 09:52 AM.

  3. #23

    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by ZerocoolAstra View Post
    do explain please!
    0EV to -1.0EV is a reduction of 1 stop of light.

    1/8 power to 1/16 power is also a reduction of 1 stop of light.
    the EV setting of -1.0 is a RELATIVE setting, while manual setting to 1/8th of power is an absolute setting.
    if you set the flash to 1/8th then it fires each time at 1/8th of its max power output. if you set it to -1.0EV then it will fire one stop lower than what the cam measures, ie. the cam thinks it should fire at full power so it it will fire at 1/2 power. you are not getting constant light output.
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  4. #24
    Senior Member B-setting's Avatar
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    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by Michael View Post
    the EV setting of -1.0 is a RELATIVE setting, while manual setting to 1/8th of power is an absolute setting.
    if you set the flash to 1/8th then it fires each time at 1/8th of its max power output. if you set it to -1.0EV then it will fire one stop lower than what the cam measures, ie. the cam thinks it should fire at full power so it it will fire at 1/2 power. you are not getting constant light output.
    interesting michael...

    but why is it that when the flash EV setting is stopped down by 1, i.e. -1.0 EV, the output is halved?

    is this a linear relationship? meaning, if the EV is now stopped down to -2.0 EV, the output is
    1/2 x 1/2 = 1/4 ??

    in any case, why do flash manufacturers incorporate this EV adjustment on flashes? what is its actual use?

    thanks for advice..

  5. #25

    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by B-setting View Post
    interesting michael...
    but why is it that when the flash EV setting is stopped down by 1, i.e. -1.0 EV, the output is halved?
    is this a linear relationship? meaning, if the EV is now stopped down to -2.0 EV, the output is
    1/2 x 1/2 = 1/4 ??
    in any case, why do flash manufacturers incorporate this EV adjustment on flashes? what is its actual use?
    thanks for advice..
    1 EV or f-stop halves the amount of light reaching the film/sensor. That is how a EV is defined.
    why include EV setting? well if you operate a flash in manual you dont need it. But if you operate it in automatic mode then the cameras computer determines the required flash amount based on what it measures. if you have for example the situation of a very dark background with 1 person in the foreground automatic flash will tend to overexpose the person as the cam tries to brighten the background as well... with the EV adjustment you can tell the cam to power down the flash and hence to avoid overexposure. the EV adjust for the flash (as for the normal cam exposure) is needed when the cam's computer reaches its limit and you need some human thinking....
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  6. #26

    Default Re: How to use SB-400 in manual mode?

    Ditto, but do bear in mind that one EV is equivalent to one stop, or step.

    Also, Nikon's DSLRs are calibrated differently from most other manufacturers at 12% grey instead of 18% grey. That factors in quite prominently in metering usage.

    What I like about using EV as my main metering reference is that it makes pre-visualization so much easier!

  7. #27
    Senior Member ZerocoolAstra's Avatar
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    Default Re: How to use SB-400 in manual mode?

    ok thanks guys for trying to explain...
    I haven't had the chance to experiment for myself (the only way I can convince myself), but I think I must do so at the next opportunity.

    To me I think that there should not be any difference between -1.0 flash EV and halving the flash output, all other conditions/settings being equal of course.
    "Reflectivity" is a concept I need to think about a bit more. Thanks Dream Merchant for getting me thinking!
    Exploring! :)

  8. #28

    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by ZerocoolAstra View Post
    ok thanks guys for trying to explain...
    I haven't had the chance to experiment for myself (the only way I can convince myself), but I think I must do so at the next opportunity.

    To me I think that there should not be any difference between -1.0 flash EV and halving the flash output, all other conditions/settings being equal of course.
    "Reflectivity" is a concept I need to think about a bit more. Thanks Dream Merchant for getting me thinking!
    there is no difference between -1.0EV and halving flash output.... the difference is where you start.... put it that way, if you set the flash at 1/8th then it fires at 1/8th of full strength, always. if you set it at -1.0EV is fires 1 stop slower than measured, i.e. if the cam determines a flash output of 1/8 then it fires at 1/16, or it the cam determines 1/2 then it fires at 1/4... so you see the output is not constant.
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  9. #29
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    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by ZerocoolAstra View Post
    do explain please!
    0EV to -1.0EV is a reduction of 1 stop of light.

    1/8 power to 1/16 power is also a reduction of 1 stop of light.
    My guess is for -1.0EV case, it will still meter object and fire the flash power according but the output will be underexpose the subject by -1.0EV via flash . (Just like in aperture priority, u can set the exposure you want)

    Whereas , for 1/8 to 1/16 . There is not flash metering involve or TTL. Thus, no matter how bring or how dark the object is , the flash power will be reduced .

    Not sure if I am right
    Last edited by RedSuns85; 18th January 2010 at 09:10 PM.

  10. #30

    Default Re: How to use SB-400 in manual mode?

    Quote Originally Posted by RedSuns85 View Post
    My guess is for -1.0EV case, it will still meter object and fire the flash power according but the output will be underexpose the subject by -1.0EV via flash . (Just like in aperture priority, u can set the exposure you want)

    Whereas , for 1/8 to 1/16 . There is not flash metering involve or TTL. Thus, no matter how bring or how dark the object is , the flash power will be reduced .

    Not sure if I am right
    you are right
    Never forget rule 5
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