I've been into the hobby a little less than a year now and I have the
same question in mind for some months now.
thanks for the simple and very helpful tip.
Bird
From: "Jan van Wijk" <[EMAIL PROTECTED]>
To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
Date sent: Mon, 05 Feb 2001 20:03:21 +0100 (CET)
Subject: Re: EV adjustments???
Send reply to: [EMAIL PROTECTED]
On Mon, 5 Feb 2001 11:37:34 -0500, dosk wrote:
>> Note however that in the two examples above, 2.8->2.0 is a full f-stop
>difference
>> (+1 EV) while 2.8->3.5 is only half a stop (- 1/2 EV) ...
>
>I don't understand this part. Can you elaborate further?
>
Sure!
The term "stop" indicates doubling or halving the exposure.
For the shutter this is why the major speeds roughly double in
value as
in:
2 4 8 15 30 60 125 250 500
For the aperture, we need the same effect, however the aperture is
measured differently. The aperture (f) value equals the effective
opening
divided by the focal length. So a 50mm f2.0 lens would roughly
have a 25mm
diameter opening.
The amount of light does not relate in a linear way to the opening
diameter but rather to the surface. The relation between the two is
square-root, so for doubling or halving the the surface (and amount of
light), we only need to multiply or divide the f-value with the
square-root of 2 wich is about 1.4
So to make this rather long story short, a range for full f-stops would
be:
1 1.4 2 2.8 4 5.6 8 11 16
Now your 3.5 is in between 2.8 and 4, and is about half a stop 'slower'
than 2.8
Other 'well known' half-stop values are 1.2, 1.7, 2.5 and 4.5 although
some of these are not exactly 'in the middle'.
Half a stop would be the square-root of the square-root of 2, wich is a
1.19 factor.
>
>> And since your MZ-M is a manual camera, it only affects the readout of
>> the
>meter,
>> changing the compensation-dial on a manual camera without changing
>aperture (f-stop) or
>> shutter (time) doesn't change the exposure at all ...
>
>No, the ZX-M has full auto exposure program plus aperture and shutter
>priority settings, and also motor wind and advance. Only the focusing is
>manual. (Best of this type around, which is why I bought it...)
Yes you are right of course, I guess I only related "manual" to any ZX-M
feature :-)
Regards, JvW
---------------------------------------------------------
Jan van Wijk; www.fsys.demon.nl
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