Richard Knoppow (dickburk@ix.netcom.com)
Wed, 19 May 1999 18:47:36 -0700
At 05:59 PM 5/19/99 -0700, you wrote:
>John Erbes wrote:
>>
>> At 11:39 AM 5/19/99 -0700, Gary Miller wrote:
>> >Speaking of the difference of shooting outdoors as opposed to shooting in
>> >the studio, why are the outdoors negatives so much more dense. If I am
>> >taking a meter reading both inside and outside shouldn't the negatives
>> >ultimately be the same density if I am rating the film at the same ASA. I
>> >know that Carl has mentioned the difference between using a spot meter
>> >reading outdoors as opposed to a flash meter reading in the studio. But
>> >shouldn't it all be relative? My shoots from outside are much more
dense and
>> >stained than my studio shots.
>>
>> Gary,
>> It's my understanding that film speeds are slower indoors typically by a
>> stop or so as compared to their rated outdoor speed. I don't know why,
>> but I'm sure that someone on the list will explain.
>>
>> John Erbes
>
>In THE BOOK OF PYRO by G. Hutchings on page 66 he discusses the
>increased densities of the negs. due to the internal flare bouncing off
>the inside of the camera. The increase is, according to his testing,1
>stop in added exposure.
>
This just can not be made as a general statement. First, the amount of
flare is going to be dependent on the construction of the camera. Some
cameras have excellent flare baffling, post 1954 Roleiflex's and
Rolleicords for instance. Secondly, flare affects mostly the toe exposure
and has little effect on the overall density of a negative. The statement
also assumes that interior lighting is going to be more flare free than
exterior lighting. Perhaps true for carful studio lighting but not as a
general statement.
This is simply not the cause of a consistent large difference in the
exposure of negatives made under two conditions.
One possible cause, if the interior lighting is via strobe is inaccurate
shutter speed. For strobe the shutter speed has no effect in controlling
exposure. It mearly has to open before the flash and shut after it. For
exposures with continuous light, as with daylight, the shutter is going to
have a profound effect. Mechanical shutters are not exactly precision
instruments, especially old LF shutters. An Ilex, for instance, was speced
for only +/- one stop when new, they can easily be a stop or more off
speed. Other large shutters are not much better.
About the only way you can tell is to use a shutter calibrator like the
one available from Calumet. They are not expensive and will blow the
whistle on inaccurate or inconsistent shutters.
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
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