>
>>
>> well I spent a few hours with a sekonic l-358 in reflective
>> mode showing raw EV values and my bronica etrsi with the
>> lenses set to T i.e. shutter open all the time and the
>> sekonic where the film back would be. I measured the light
>> loss vs infinity focus for all 6 of my lenses at every
>> interval marked on the distance scale. The results are STRANGE..
>>
>
> I'm not surprised that the results are strange. You are using the
> exposure
> meter in a configuration it was not designed for. The meter probably has
> a
> simple optical system which when combined with the camera's optical system
> (the lens) gives a result which is different to just projecting the image
> onto a simple measuring surface. For example, how well was the optical
> system of the meter aligned with the optical axis of the lens ? What if
> the
> resultant image falls a significant distance in front/behind the measuring
> cell ? Do you have a TTL meter for the Bronica ? It probably wouldn't
> read
> to 1/6 of a stop, but it will be designed to actually read accurately TTL.
>
> ...Wayne
I cant see why the meter would lie in a repeatable and consistent manner.
In reflected mode it has a measurement angle of 54 degrees and placed
inside the bronica it should cover the entire inside of the mirror
chamber. since all it is measuring is a shaft of light. Also given the
same f stop it gives the SAME ev value for EACH of the lenses focused at
infinity which makes sence since they all should be providing the same
amount of light independantly of the design of the lens. AND the
measurements are relative to infinity focus so I am simply measuinr ev
values and not shutter speed, iso and f stops.
My guess is that it is variation in the distance from the appature blades
to the film/meter that matters. With the zoom the appature does not seem
to move with focus distance or focal length with the other lenses it does
move.
I repeated the results with the aeIII primism which displays the shutter
speed in half stops and got very simular results - bearing in mind the
lower measurement accuracy. Certainly there is no indication of a decrease
in shutter speed with the aeIII when I compare infitnity on the zoom at
220mm and 1m on the zoom @220mm focal length and acording to the maths
there should be half a stop loss.
Next I plan to take a set of grey card shoots in manual using my sekonic
measurements for different distances if they all come out the same grey
then the measurements are vindicated.
James
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