[LargeFormat] I need a formula.

[Les Newcomer]

The academic answer is no, Watt seconds is the unit of energy used, not 
all of it is converted into light, some lights are more efficient than 
others, efficiency also changes with age of the flash tubes.

Some flash manufactures' tried to standariize on joules, but there are 
problems with that too.

obviously reflectors play a big part too.

I'm sure somewhere out there there is a standard of lumens seconds of a 
particular type (difused, specular) of a certain amouont to cause a 
certain rise in density,  but it's probably so far away from reality as 
to be useless.


That said i'm sure there are people on this list that can tell you with 
their rig it will take this amount, etc.




Les



On Sunday, August 18, 2002, at 07:04 PM, John Pass wrote:

> Howdy,
>
> Is there a formula that would tell me
> the amount of light I need (preferably
> in WS) for any give film speed and
> apeture.  For example (an extreme one),
> if I'm in a pitch black studio and want
> to expose an 8x10 sheet of tmx at f64 how
> much power would I need?  I know at f64 I'm
> probably going to need mirrored solar collectors
> pointing down a skylight in the roof.
>
> Thanks for your help!
>
> John
>
>
>
>
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