On Thu, 10 May 2001, Rob Studdert wrote:
> Hi,
>
> I'll have a go (I hope there aren't 100's of replies preceding mine). Firstly the
> initial over-exposure would most probably have been due to the camera
> metering setting the exposure to achieve an overall 18% gray. Since I
> assume that a high proportion of the shot was dark (you didn't describe the
> framing)
I am sorry that I didn't describe the framing. It was the white
elliptical dial with the hour, minute, second and alarm hand. The small
bulb was located at the circumference of the ellipse to illuminate the
dial and the rest of the frame absolutely dark. I took the first shot
with all the lights of the room switched off.
> and you wished it to stay that way I would have suggested that you
> underexpose by about two stops, this doesn't simply mean stopping down
> the lens two stops and increasing the shutter speed, one parameter must
> not be changed or otherwise the absolute exposure remains the same. For
> example if the meter said 2 sec at f4.5 then you could have set the shutter
> speed to 8 seconds or the aperture to f8 + 1/2 but not changed both.
Sorry, I could not understand '+1/2'. Do you mean half stop exposure
compensation is allowable?
> In the second case I assume that the film that you used suffered what is
> known as reciprocity failure
Oooooh! I absolutely forgot about the reciprocity failure. Though I read
it in books but it was not in my mind before/composing the shot. Thank you
very much for that.
> since the amount of light striking the film was
> below the films low light threshold. Many films behave badly when exposed
> to very low light most often the relationship between shutter speed and
> aperture becomes non-linear as exposure times creep past regular exposure
> periods ie longer than a second. Often the dye layers in the film respond
> differently creating interesting colour shifts or casts as well.
>
> When you are working in low light situations unless you are prepared to do
> some research to determine the response and limitations of the film that you
> are using it is best to use faster films and wider apertures in order to keep
> the shutter speed relatively fast ie not longer than a few seconds.
I got your point.
> I would guess that your camera and light meter are fine, be sure to
> experiment next time and write down the settings so that you can check
> them against what worked :-)
Surely, I should do that.
> Cheers,
>
> Rob Studdert
> HURSTVILLE AUSTRALIA
Thank you very much for your help.
With best regards,
Ayash Kanto.
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