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Sunny 16 rule?



 
 
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  #11  
Old August 29th 04, 09:48 PM
Roland Karlsson
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Alan Browne wrote in news:_ZqYc.14049
:

From time to time you will see postings that suggest the
manufacturers do not follow the ISO sensitivity very well.


Yepp - the ISO sensitivity for film is rather easy to define.
You can build a brand independent test equipment for the film
you want to test. There are differnet definitions for negative
and positive film though.

But - how do you test that a digital camera follows the ISO
specification? Compact digital cameras have a non removable
lens. How do you know what F-stop the camera really chooses?
How are you sure that the camera really chooses the correct
exposure time? Then - a digital camera may make some "hokus pokus"
when doing the actual translation from charges to digital values,
and it probably does. It might apply some levelling of the
values before converting to e.g. JPEG.

Now - you can of course test wether the camera's exposure
meassurement system gives the same result as a well callibrated
exposure meter. But, cameras have never been so good att doing
that - that was the case even for film based cameras. And,
even worse, modern cameras have some kind of "intelligent"
exposure meassurement, evaluating the picture. Now we are
talking about serious "hokus pokus".

So - in short. Yes there might be problems with what the camera
call ISO 100. The G2 I have have ISO 50. Most other compact
dicicams have ISO 100 as lowest. But tests - e.g. at www.dpreview.com -
shows that this is the same sensitivity. So - either G2 lies about
being too bad or the other lying about being too good. What do
you think is the case?


/Roland
  #12  
Old August 29th 04, 09:53 PM
Roland Karlsson
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"David J. Littleboy" wrote in
:

Does the "sunny 16" exposure rule apply to digicams?


Yes.


No. It applies to negative films where there's enough latitude that
the printer can rescue your incorrect exposures. It's advisable to use
the meter (and the histogram) with slide films and digital cameras, or
with negative films if you care about getting the most from the film.


The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.

Of course, a meeter is needed for the shadows. But for well lit parts,
nope not at all.


/Roland
  #13  
Old August 29th 04, 09:53 PM
Roland Karlsson
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"David J. Littleboy" wrote in
:

Does the "sunny 16" exposure rule apply to digicams?


Yes.


No. It applies to negative films where there's enough latitude that
the printer can rescue your incorrect exposures. It's advisable to use
the meter (and the histogram) with slide films and digital cameras, or
with negative films if you care about getting the most from the film.


The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.

Of course, a meeter is needed for the shadows. But for well lit parts,
nope not at all.


/Roland
  #14  
Old August 29th 04, 10:34 PM
grim
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"Roland Karlsson" wrote

The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.


Well, the brightness of the sun at the Earth isn't a constant. It's 7%
brighter in January than in July (the Earth is 3.5% closer to the sun in
January). Might not make much of a difference to what shutter speed you use,
but it's just one variable (among many other more important ones) that can
vary the intensity of sunlight in a picture.


  #15  
Old August 29th 04, 10:34 PM
grim
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"Roland Karlsson" wrote

The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.


Well, the brightness of the sun at the Earth isn't a constant. It's 7%
brighter in January than in July (the Earth is 3.5% closer to the sun in
January). Might not make much of a difference to what shutter speed you use,
but it's just one variable (among many other more important ones) that can
vary the intensity of sunlight in a picture.


  #16  
Old August 29th 04, 10:54 PM
Alan Browne
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Roland Karlsson wrote:

Now - you can of course test wether the camera's exposure
meassurement system gives the same result as a well callibrated
exposure meter. But, cameras have never been so good att doing
that - that was the case even for film based cameras. And,
even worse, modern cameras have some kind of "intelligent"
exposure meassurement, evaluating the picture. Now we are
talking about serious "hokus pokus".


For one thing, I would expect that if I light a grey card such
that an incident meter gives me a reading (let's say f/5.6 @
1/15) and that I shoot the the image with that setting... when I
look at the image rgb channels, they should:

1) each show an equal level (or very nearly so) (R=G=B) AND

that level should be 18% grey... which according to at least
http://astro.umsystem.edu/apml/ARCHI.../msg00561.html
is R=G=B=115 (scale of 0..255).

(One fellow in the link above scanned a grey card and got
121,121,121 which is pretty close).

http://www.aim-dtp.net/aim/calibration/middle_gray/ near bottom
suggests that the mid point (R=G=B=128) is the correct value.

In any case, if R,G,B are each in the range 110 - 130 for a
properly exposed shot of a grey card, then it is likely the
metering of the camera is correct.

Cheers,
Alan


--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--
  #17  
Old August 29th 04, 10:57 PM
Mark M
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"Ken Scharf" wrote in message
. ..
Does the "sunny 16" exposure rule apply to
digicams?


Only as a rough guide.
You will discover that it is often too dark with either digital or slide
film.
You'll have to experiement with your camera.
As for my 10D, 16 is usually too dark.
F11 is closer--but then it varies a lot due to atmospheric conditions and
other factors.


  #18  
Old August 29th 04, 10:57 PM
Mark M
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"Ken Scharf" wrote in message
. ..
Does the "sunny 16" exposure rule apply to
digicams?


Only as a rough guide.
You will discover that it is often too dark with either digital or slide
film.
You'll have to experiement with your camera.
As for my 10D, 16 is usually too dark.
F11 is closer--but then it varies a lot due to atmospheric conditions and
other factors.


  #19  
Old August 29th 04, 11:04 PM
David J. Littleboy
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"Roland Karlsson" wrote in message
...
"David J. Littleboy" wrote in
:

Does the "sunny 16" exposure rule apply to digicams?

Yes.


No. It applies to negative films where there's enough latitude that
the printer can rescue your incorrect exposures. It's advisable to use
the meter (and the histogram) with slide films and digital cameras, or
with negative films if you care about getting the most from the film.


The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.


If you care about your exposures, you'll find that Sunny 16 is rarely
correct.

Of course, a meeter is needed for the shadows. But for well lit parts,
nope not at all.


It's not just shadows: sunny 16 simply is simply wrong too much of the time
to use for slides and digital.

David J. Littleboy
Tokyo, Japan






  #20  
Old August 29th 04, 11:04 PM
David J. Littleboy
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Posts: n/a
Default


"Roland Karlsson" wrote in message
...
"David J. Littleboy" wrote in
:

Does the "sunny 16" exposure rule apply to digicams?

Yes.


No. It applies to negative films where there's enough latitude that
the printer can rescue your incorrect exposures. It's advisable to use
the meter (and the histogram) with slide films and digital cameras, or
with negative films if you care about getting the most from the film.


The sunny 16 rule is very dependable in bright sunshine as our
Sun is a very dependable source of light. If it was not, we would
be in great trouble.


If you care about your exposures, you'll find that Sunny 16 is rarely
correct.

Of course, a meeter is needed for the shadows. But for well lit parts,
nope not at all.


It's not just shadows: sunny 16 simply is simply wrong too much of the time
to use for slides and digital.

David J. Littleboy
Tokyo, Japan






 




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