Sunny 16 rule?

In article ,
David J. Littleboy wrote:

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

Certainly with the Canon DSLRs, and the raw convertor in Photoshop, you get
behaviour which is rather more forgiving than slide film. In general,
rescuing something that's been underexposed by 2 stops is feasible, and you
can still get detail back from something that's nominally up to a stop past
blowout sometimes.

In article ,
David J. Littleboy wrote:

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

Certainly with the Canon DSLRs, and the raw convertor in Photoshop, you get
behaviour which is rather more forgiving than slide film. In general,
rescuing something that's been underexposed by 2 stops is feasible, and you
can still get detail back from something that's nominally up to a stop past
blowout sometimes.

wrote:

In message ,
Alan Browne wrote:


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


Which could mean that claims of noise at specific ISOs are meaningless.

If camera A has the same noise at ISO 200 that camera B has at ISO 100,
who's to say that they both not really ISO 140, and have the same noise?


Correct exposure would be an average of many pixels which would
reduce the noise and get one close to the correct ISO, I would
think. The "film" definition of ISO:

[15.4 • f.no^2 / (cd/m2 • t) ] = ISO numbers for 18% grey exposure

needs only be met such that the R=G=B = aprox 115 ... 128* (of
0..255) to claim meeting an ISO setting. The variance about the
average value (of a few dozen pixels) would be the noise.

So photograph a grey card with an incident metered reading under
5000K or hotter light and then look at those RGB values... would
also give you a fair survey of the noise of a a particular
sensor. If the RGB values are much above 128, then the ISO
setting of the camera is biased high.

Cheers,
Alan.

*
http://astro.umsystem.edu/apml/ARCHI.../msg00561.html
http://www.aim-dtp.net/aim/calibration/middle_gray/

--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

jpc wrote:

On Mon, 30 Aug 2004 00:07:02 GMT, wrote:


In message ,
Alan Browne wrote:


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

Which could mean that claims of noise at specific ISOs are meaningless.

If camera A has the same noise at ISO 200 that camera B has at ISO 100,
who's to say that they both not really ISO 140, and have the same noise?



In the film world, an ISO number is fundamental property of the
emulsion. In the digital world an ISO number is simply a misnamed gain
setting. Unless the camera firmware is heavily filtering the image at
high A/D gain settings--aka iso numbers--the sensor noise at gain 1 is
only multipied by successive factors of two.

The definition of ISO film sensitivity is rooted in physics:

[15.4 • f.no^2 / (cd/m2 • t) ] = ISO numbers for 18% grey exposure.

Thus, as in my reply to JPS, a simple test can be made to see how
well a given camera follows the ISO definition for 'film'
sensitivity. Of course an independant measurement of the light
level needs to be made.

Cheers,
Alan.


--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

Fred McKenzie wrote:
Others caught the apparent discrepancy in shutter speed. However, there is
another factor to consider. While the moon appears white to the eye, it is not
100 percent reflective. In other words, it is a big gray rock.

With a rule based on incident light (such as Sunny-16) the
correct exposure is always the same regardless of the color or
reflectance of the object.

An in camera meter reading can be fooled by the refelctance of
the object which is why exp comp is provided. An incident meter
reading is not affected by the reflectance of the subject (in
simple situations such as this...).



For the moon to look the way you expect (more white than gray), an additional
stop would be appropriate. Therefore your 1/200 second would be right on!

No, that would be an overexposure.



--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

wrote:

I would think so too. The metering on my 10D exposes a grey card under
the sunny f16 sun at about 128 (out of 255). If I use sunny f16 out in
the open, it registers around 90. In midtown-Manhattan, it registers
around 120.

Nice info.- kinda puts it to rest.

Interesting thread, but under what circumstances - today - would one
want or need the sunny 16? Back when meters were atrocious or it was
hugely expensive to buy a good one, understood. Back when one might have
forgotten one's light meter and wanted an approximation, understood.

--
John McWilliams

wrote:

I would think so too. The metering on my 10D exposes a grey card under
the sunny f16 sun at about 128 (out of 255). If I use sunny f16 out in
the open, it registers around 90. In midtown-Manhattan, it registers
around 120.

Nice info.- kinda puts it to rest.

Interesting thread, but under what circumstances - today - would one
want or need the sunny 16? Back when meters were atrocious or it was
hugely expensive to buy a good one, understood. Back when one might have
forgotten one's light meter and wanted an approximation, understood.

--
John McWilliams

wrote:

I would think so too. The metering on my 10D exposes a grey card under
the sunny f16 sun at about 128 (out of 255). If I use sunny f16 out in
the open, it registers around 90. In midtown-Manhattan, it registers
around 120.

Nice info.- kinda puts it to rest.

Interesting thread, but under what circumstances - today - would one
want or need the sunny 16? Back when meters were atrocious or it was
hugely expensive to buy a good one, understood. Back when one might have
forgotten one's light meter and wanted an approximation, understood.

--
John McWilliams

On Mon, 30 Aug 2004 10:44:53 -0400, Alan Browne
wrote:

jpc wrote:

On Mon, 30 Aug 2004 00:07:02 GMT, wrote:


In message ,
Alan Browne wrote:


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

Which could mean that claims of noise at specific ISOs are meaningless.

If camera A has the same noise at ISO 200 that camera B has at ISO 100,
who's to say that they both not really ISO 140, and have the same noise?



In the film world, an ISO number is fundamental property of the
emulsion. In the digital world an ISO number is simply a misnamed gain
setting. Unless the camera firmware is heavily filtering the image at
high A/D gain settings--aka iso numbers--the sensor noise at gain 1 is
only multipied by successive factors of two.

The definition of ISO film sensitivity is rooted in physics:

[15.4 • f.no^2 / (cd/m2 • t) ] = ISO numbers for 18% grey exposure.

My reference book (Photographic Materials and Processes, Focal Press
1986 pp 54-56) defines a film ISO number as 1/H x .8 where H
(exposure) is measured in Lux sec. At this exposure the film has an
optical density of .1 over the fog. The .8 is safety factor.

We agree on the exposure, but I don't follow how the f# enters into
the equation. Could you explain further or supply a reference


jpc

On Mon, 30 Aug 2004 10:44:53 -0400, Alan Browne
wrote:

jpc wrote:

On Mon, 30 Aug 2004 00:07:02 GMT, wrote:


In message ,
Alan Browne wrote:


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

Which could mean that claims of noise at specific ISOs are meaningless.

If camera A has the same noise at ISO 200 that camera B has at ISO 100,
who's to say that they both not really ISO 140, and have the same noise?



In the film world, an ISO number is fundamental property of the
emulsion. In the digital world an ISO number is simply a misnamed gain
setting. Unless the camera firmware is heavily filtering the image at
high A/D gain settings--aka iso numbers--the sensor noise at gain 1 is
only multipied by successive factors of two.

The definition of ISO film sensitivity is rooted in physics:

[15.4 • f.no^2 / (cd/m2 • t) ] = ISO numbers for 18% grey exposure.

My reference book (Photographic Materials and Processes, Focal Press
1986 pp 54-56) defines a film ISO number as 1/H x .8 where H
(exposure) is measured in Lux sec. At this exposure the film has an
optical density of .1 over the fog. The .8 is safety factor.

We agree on the exposure, but I don't follow how the f# enters into
the equation. Could you explain further or supply a reference


jpc