Sounds to me like you just doubled the exposure on the subject and just
blew all the highlights.
Chuck Norcutt
Ken Norton wrote:
>> But a guide number won't do you much good for a fill flash.
>>
>
> Why not?
>
> A guide number provides a known element in the equation for proper exposure
> that includes the following:
>
> 1. ISO sensitivity of the film or digital sensor
> 2. Ambient light level (basis for everything)
> 3. Effective flash brightness
> 4. Subject-to-flash distance.
>
> My working method would be something like this for outdoor fill on bright
> sunny day:
>
> 1. Determine the ISO I'm going to use for this--in lower light conditions or
> indoors, steps 1 and 2 are sometimes recursive. For bright sunny day, I'm
> usually at ISO 100.
>
> 2. Measure ambient light level and place the exposure of the ambient high,
> low or at the "proper" exposure. If I'm balancing the light in such a way
> that the ambient is dead-on, then it will look something like a Sunny-16
> exposure, or inotherwords some equivalent to F16 at 1/125. However, that
> means that with a camera like an OM with 1/60 flash sync speed, that makes
> it F22 at 1/60. So, I may grab the polarizer to knock off two stops and give
> myself F11 at 1/60, but when using film I prefer to run my ambient either a
> stop high or a stop low, so I'll do F8 at 1/60 with polarizer. With digital
> cameras, we have a little more flexibility, so my base exposure of F16 at
> 1/125 can go up to 1/180 or so, and with a polarizer, I can get back down to
> the F5.6-F7.1 region. (this is one area where the A1 shines because of the
> almost unlimited flash-sync speeds). But, for this example, let's stick
> with F16 at 1/125 and assume that it works with the camera.
>
> 3. A guide number is essentially the following equation: "GN = Distance *
> F-number". We have two numbers already. The published or calculated or
> metered GN of the flash, either electronic or bulb. .
>
> 4. We have the F-number from step #2, therefore, to determine flash distance
> from the subject we use the following: Distance = GN / F-Number. (you will
> need to make sure you are working in feet or meters). So, based on this
> calculation you will know exactly how far away from the subject to place
> your flash.
>
> Or the simplest way is to waste one bulb with a flash meter and adjust
> distance by estimation.
>
> AG (I don't even play Dr. Flash on television) Schnozz
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