ISO and actual sensitivity in DSLR's (D70, *istD, 20D, S3...)

Roland Karlsson wrote:

Alan Browne wrote in news:d21cm6$s5u$2
@inews.gazeta.pl:


Appolgies, I thought you were replying to me. My news reader does a bad
job of organizing refreshes.



NP - mozilla's that bad eh?

What's supplied with the Mandrake distro is worse. And slow.


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-- e-meil: there's no such thing as a FreeLunch.

Jim wrote:

However, in my case, I tested my D70 when I first received it. I found that
the exposure of a gray card as reported by the built in meter (using spot
meter) is correct. That is to say, it always agreed with the sunny 16 rule.
I found that the resulting photographs showed the expected histogram shape.
I have since found that the outdoor photographs need very little if any
correction using the levels command.

I also found that the exposure of a gray card with the built in flash is
correct. However, the flash does under expose my black dog about 1/2 stop.
That little underexposure is easily corrected, but annoying none the less.
The manual does caution that photographs of dark objects may be
underexposed. I suppose that my experience agrees with the caution.

Typically dark objects end up highly overxposed without flash comp/exp
comp. But the D70 (IIRC) uses a smaller scale F5 matrix derived
metering system, which is very accurate.

As to your grey card, I have two grey cards. One is a full stop paler
than the other. But I know which one is right.

Cheers,
Alan

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-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
wrote:


Quicker to set strobes with an incident flash meter. Though I am
developing a worrisome, guilt inducing chimping habit when outdoors with
the D7.

I agree with setting the strobes with an incident meter, but the
histogram is the perfect tool for fine tuning exposures. As for
chimping, I have spent big bucks fine tuning medium format exposures
with polaroid so I don't have any guilt about chimping. Most pros
shooting digital backs are examining the images on a computer too.

In message ,
Alan Browne wrote:


We've seen the occasional postings about the ISO setting and the actual
sensitivity.

I picked up Casseur D'Images (No. 271, March 2005) and among other
things they did tests on a variety of DSLR's and one ZLR. (p. 169)

They rounded the results when close to the standard 1/3. But where a
little less clear cut, they put a +/- to indicate not quite in the 1/3 zone.

They describe, in punishing detail, the test method, references, math,
etc. Unfortunately, the 7D is not part of the grouping, but I'll take
sollace in the A200 results. Minolta have long been known for their
consistency in metering and exposure.

What exactly are they measuring? The metering system, or the
sensor/RAW_data?
--


John P Sheehy

In message ,
Roland Karlsson wrote:

"Pete D" wrote in
:

And as has been said before, it does not matter one tiny little jot as
long as the photos come out right.

You are not of the old school I see

It does matter.
- if you use an external meter.
- when comparing the sensitivity of camera systems.
- when using external flash.
- etc

But - if you just take pictures and like them - then
the technicalities behind the making of the photo is
of course uninteresting.

But - it does matter - even if you don't care

The problem I see with all this is that proper metering for the selected
ISO is not connected, necessarily, to a good exposure.

You could have ten different cameras that all selected the same
("correct") f-stop and shutter speed when pointed at the same white card
under the same lighting, and one could have 5 stops of RAW headroom, and
another might have a 1/2 stop. You could work around this and get
better exposures, and a camera that you are intentionally metering
"wrong", with EC, might give you better exposures.
--


John P Sheehy

On Fri, 25 Mar 2005 20:42:27 -0500, McLeod
wrote:

On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
wrote:


developing a worrisome, guilt inducing chimping habit when outdoors with



chimping, I have spent big bucks fine tuning medium format exposures
with polaroid so I don't have any guilt about chimping. Most pros

chimping ?

Pllease explain.

Glenn

On Sat, 26 Mar 2005 07:31:34 -0500, Glenn
wrote:

chimping ?

Pllease explain.

Photographer hunched over the back of his camera looking at the lcd
going "Oooo! oooo!"

McLeod wrote:

On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
wrote:


Quicker to set strobes with an incident flash meter. Though I am
developing a worrisome, guilt inducing chimping habit when outdoors with
the D7.


I agree with setting the strobes with an incident meter, but the
histogram is the perfect tool for fine tuning exposures. As for
chimping, I have spent big bucks fine tuning medium format exposures
with polaroid so I don't have any guilt about chimping. Most pros
shooting digital backs are examining the images on a computer too.

I know. It's just so out of character for me. er, was.

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-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

wrote:


What exactly are they measuring? The metering system, or the
sensor/RAW_data?

Sensor. They go through a blow by blow description of the test on p
169. Basically, they're looking for the sensor data converted to JPG to
be 118/255 (R,G,B) to indicate successful grey card measurement. They
do not delve into the extremes of the curve.

Cheers,
Alan.

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: there's no such thing as a FreeLunch.

On 26 Mar 2005 in rec.photo.digital.slr-systems, Glenn wrote:

chimping ?

Pllease explain.

http://www.wordparts.com/archives/2004/09/30/chimping

http://www.chimping.com/

Mo

http://www.wisenut.com/search/query.dll?q=chimping

--
Joe Makowiec
http://makowiec.org/
Email: http://makowiec.org/contact/?Joe