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Overpowering sun, correct power from flash



Hi Neil, Here is a tutorial from 2012. I am hoping for some help with a tough shoot this afternoon. Bright sun, high school senior. There will be no shade at this very bright location. I could have an assistant hold the shade but that will just mean I'll end up with totally blown out background. (Tried to resched to later, but that was a no go). 

I was wondering if you remember what the power setting was on your flash? I could not find that in the text. I understand you used the distance scale, but at what power on the (manual) flash? Was it manual at full power? And I guess the real question is how do you determine the power level? With a flash meter? I understand that you first exposed for the bright background (here you used the sky). But then to properly expose your model's face, how did you decide at what power level to put your flash?

I wonder if a single SB910 will be enough today. 

Thank you!



(Excerpt)

The Nikon SB-910 and Canon 600EX-RT (vendor) speedlites have a distance scale on the flash. This allows you to balance that equation for correct manual flash exposure – aperture / ISO / distance / flash power.

Since the aperture and ISO is given for us … and we have our speedlight to manual output, then the distance scale will tell us approximately how far to hold the flash from your subject. Of course, a few test shots will allow you to finesse this for better exposure. I worked with the flash at full output.

Comments


  • Given Jorg's answer here* in this tutorial (answer #3) and given that Neil said 'Nailed it' is it correct to assume that with Sunny 16 flash power with portraits should always be manual 1/1 (full power)? (Unless you want some unusual moody or creative lighting).

    If so I am sure that must change when using more than one flash..... say a fill as well or just a second light on the other side?


    Like the model here (in above linked lesson) I am hoping to put student's back to the sun, thus her face in shadow and so I'll need to light that up and hopefully get the background properly exposed or at least in the ballpark.

    *Neil had asked readers to guess the settings he used for a photo at the top of the tutorial. Here is Jorg's answer: (Neil responded 'Nailed it.')

    3Jörg says

    April 1, 2014 at 6:11 pm

    So I’ll start by saying: 1/250s @ F11 @ ISO100 and full flash power

    and here is why: 1/250s (max sync speed of the D4) for most efficient flash use
    Sunny 16-rule gives 1/100 @ F16 @ ISO 100 which is roughly equivalent to 1/250s @ F11 @ ISO100
    You probably needed all the speedlight could offer when shooting against the sun, so full manual flash.

    Thanks a lot for the post, Neil. Did you zoom in the flash reflector to ‘focus’ the light output?

    Jörg



  • The flash needs to be on the camera for the flash to calculate the
    distance scale, with the flash on the camera it knows the camera ISO and aperture
    settings. You know the ISO, aperture set the camera accordingly, adjust the
    power on the flash till you get the correct distance while it is on the camera.
    Remove the flash from the camera and set it the correct distance to the subject.
    If you need to make minor adjustments to the flash power, just adjust your
    flash to subject distance.





  • Thank you qrickman. So, you are saying don't set the power on the flash, note the distance and adjust the flash power until the distance it suggests (of course factoring in the aperture and ISO and shutter speed) is in fact the distance you want? 




  • Adjusting the camera ISO,
    aperture or the flash power will change the distance scale.  If you know the ISO and aperture the only adjustment
    you need to make is adjust the power on the flash till you get the distance
    your looking for.  Try it.




  • Neil vNNeil vN Administrator
    Work through this tutorial: 

    This will tell you exactly what your flash settings should be. 

    btw, with Nikon flashes like the SB-900 / Sb-910  (and maybe SB-800?) you set a base ISO on the flash itself - this will give you the distance info, even when the flash is not on the camera.  (But for that specific ISO.) With Canon (and I assume Sony?), the flash needs to be on the camera for you to see the distance info. 
  • Neil vNNeil vN Administrator
    As for working with manual flash, and using the distance scale to adjust the flash power down to the level for correct exposure: 

  • Thanks very much Neil. I will read those tutorials you linked here. Appreciate it!
  • Neil, I wonder if you'd get a lot of interest if you held a math workshop. Just the math involved in topics like this thread I started, or why 250 is the ideal shutter speed, inverse square law, getting the exposure right in all kinds of situations with and without flash, using fill flash, etc.... 
  • Neil vNNeil vN Administrator
    Not much math involved, other than being able to count full stops shutter speed / aperture / ISO. 

    The Advanced Class would just focus on counting this up and down in third stops. 


  • Neil



    Sony flashes need to be on the camera for the distance scale
    to work. 
    I don’t use the distance scale
    it is easier to use the flash in TTL, off camera and lock the flash power in
    with Flash Exposure Lock and make changes to the flash power by adjusting the Flash
    Compensation at the camera, no math. 



  • English is easy too. Unless you're French. I may as well be French when it comes to math. Seriously Neil, the math is a little harder than that. For some of us anyway. I think mastering the math makes all the difference, everything else is just a work-around.
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