On Mon, 10 Oct 2005 05:39:17 GMT, Captain Blammo, <> wrote:
> > Is there a formula correlating
> > shutter/aperture/ISO with EV for the Panasonic FZ5?
>
> OK, I'm probably barking up the wrong tree here because I'm sure
> you know this and/or want something else, but here we go anyway,
> in what will no doubt seem a horribly patronising tone due to my
> probable misreading of your question:
Actually, your explanation is exactly what I was looking for. I'm a
relative newbie to photography equations, and I got a camera just this
summer. I did some reading and picked up the tradeoffs between aperture
and exposure time and ISO. EV ties it up into one neat equation.
> Modifying these settings (shutter/aperture/ISO) in their normal
> increments has the effect of halving or doubling the amount of
> exposure (Which is known as moving up or down a 'stop').
Another mystery (to me at least) explained. Thanks.
> The EV is just the value assigned to each equivalent set of
> shutter/aperture values, regardless of ISO, going from [1sec, f1.0]
> (EV 0). So EV1 would be [1/2sec, f1.0] == [1sec, f1.4] and EV2 would
> be [1sec, f2.0] == [1/2sec, f1.4] == [1/4sec, f1.0] and so on.
>
> This page has a nice table of equivalent EVs:
> http://www.chem.helsinki.fi/~toomas/photo/ev.html
I see that an aperture multiplication/division of 1.4 (approx square
root of two) is one full stop. Given that the area of a circle is
proportional to radius (or diameter) squared, this makes sense. To sum
things up,
(ISO )
EV = log_base_2(--- * exposure_time * f_ratio^2)
(100 )
The sign is tricky, because we normally deal with 1/f_ratio and ditto
for exposure time.
> So all that setting -1EV on a digicam will do is either put you
> 1 stop down on the aperture or halve the exposure time. Maybe a
> combination of shutter speed and aperture that add up to one stop
> will be used, but it's the same idea. -1EV = -1 stop of exposure. I'm
> not sure if all/some cameras will also adjust the ISO rating when
> you modify EV, but in that case -1EV may just mean going from ISO200
> to ISO100 without changing the other two settings.
Thanks again. I normally run -2/3rd EV, and yesterday was sunny. So
-2 EV was approximately 1 stop below my regular setting. That explains
why the photos only needed 2X brightening.
The FZ5 is a great little daylight camera, but has problems in
low-light situations due to running at ISO 80. It does have 100, 200,
and 400, but at the cost of noise. Being able to push it a couple of
extra stops, without the noise of regular ISO boosting, will make it
that much more useful. I might even try 3x3 binning for 9X brightness
multiplication in dark situations. That would cut 2560x1920 down to
853x640.
Since that level of deliberate underexposure is beyond the limits of
the camera's EV offset, I'd have to do it in manual mode.
--
Walter Dnes; my email address is *ALMOST* like
Delete the "z" to get my real address. If that gets blocked, follow
the instructions at the end of the 550 message.
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