Re: Using hotshoe flash with 135mm lens "Michael Yates" <mick@hdlac.org.au> wrote in
:
The idea of using the reciprocal of the focal length as a guide for
shutter speed (1/135 second shutter speed for 135mm focal length) is
basically for natural or unassisted light.
When using a flash, most especially where the flash is the primary
source of light, the extremely short duration of the flash illuminating
the scene takes the place of the shorter shutter speed.
In a completely dark room, you could lock the shutter open and walk
around with the camera, and still get a sharp picture when the flash goes
off, since you have the light for an adequate exposure for a tiny
fraction of a second. Rather than opening the shutter to provide the
light to the film, you're simply providing the light itself for a very
brief period of time.
There are some caveats, though. It will depend on the amount of
available light (without the flash) and what kind of flash metering the
camera uses. If your exposure without the flash would be within a couple
of stops of what you use *with* the flash, then you're likely exposing
the film during that entire 1/60 second, and not just when the flash goes
off. In such cases, camera movement may be an issue.
What you're talking about here is one stop, however: using 1/60
second shutter speed instead of 1/135 (or the closest setting, 1/125).
That's not a huge issue. If you're holding relatively steady and your
subject isn't moving, you might even be able to do it just fine without a
flash at all. In most cases (you never said what camera/flash you're
using), you can close the aperture *down* a stop or three, which reduces
the effect of the ambient light at 1/60, and forces the flash to provide
most or all of the exposure.
Hope this helps,
- Al.
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Al Denelsbeck
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