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

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Anonymous
March 25, 2005 1:59:13 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

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.

[There is also an article on the S3 and I'll summarize tomorrow]

Cheers,
Alan.

D70:
Setting: 200 400 800 1600
Actual: 160 320 640 1250


A200 (Minolta ZLR):
Setting: 50 100 200 400 800
Actual: 50+ 100 200 400 800


*istD:
Setting: 200 400 800 1600 3200
Actual: 250 500 1250- 2000 4000-


20D:
Setting: 100 200 400 800 1600 3200
Actual: 125 250 500 1000 2000 4000


S3:
Setting: 100 160 200 400 800 1600
Actual: 80 160 160+ 320 640+ 1250


1D Mk II
Setting: (L)50 100 200 400 800 1600 (H) 3200
Actual 64 160 320 640 1250 2500 4000


--
-- 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.
Anonymous
March 25, 2005 2:02:51 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne wrote:

> I picked up Casseur D'Images (No. 271, March 2005) and among other
Chasseur D'Images
Anonymous
March 25, 2005 9:30:04 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

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

"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote in message
news:D 202ab$rmr$1@inews.gazeta.pl...
>
> 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.
>
> [There is also an article on the S3 and I'll summarize tomorrow]
>
> Cheers,
> Alan.
>
> D70:
> Setting: 200 400 800 1600
> Actual: 160 320 640 1250
>
>
> A200 (Minolta ZLR):
> Setting: 50 100 200 400 800
> Actual: 50+ 100 200 400 800
>
>
> *istD:
> Setting: 200 400 800 1600 3200
> Actual: 250 500 1250- 2000 4000-
>
>
> 20D:
> Setting: 100 200 400 800 1600 3200
> Actual: 125 250 500 1000 2000 4000
>
>
> S3:
> Setting: 100 160 200 400 800 1600
> Actual: 80 160 160+ 320 640+ 1250
>
>
> 1D Mk II
> Setting: (L)50 100 200 400 800 1600 (H) 3200
> Actual 64 160 320 640 1250 2500 4000
>
>
> --
> -- 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.
Related resources
Anonymous
March 25, 2005 9:30:05 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In article <MdO0e.11056$C7.1258@news-server.bigpond.net.au>,
"Pete D" <no@email.com> wrote:

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

The table shouldn't be interpreted as good or bad, but informational.
Built-in exposure meters can't be used for all conditions.
Anonymous
March 25, 2005 11:25:09 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Pete D wrote:

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

For those who use an incident meter or seperate spot meters (including
myself), such information is useful.

--
-- 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.
Anonymous
March 25, 2005 1:54:52 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

"Pete D" <no@email.com> wrote in
news:MdO0e.11056$C7.1258@news-server.bigpond.net.au:

> 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 :) 


/Roland
Anonymous
March 25, 2005 1:54:53 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> "Pete D" <no@email.com> wrote in
> news:MdO0e.11056$C7.1258@news-server.bigpond.net.au:
>
>
>>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.

I do that.

> - when comparing the sensitivity of camera systems.

One of the roles of this NG.

> - when using external flash.

I do that too.

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

er, this is an equipment group. This *is* one of the things we discuss
here.

--
-- 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.
Anonymous
March 25, 2005 2:26:41 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

On Fri, 25 Mar 2005 08:25:09 -0500, Alan Browne
<alan.browne@freelunchVideotron.ca> wrote:

>For those who use an incident meter or seperate spot meters (including
>myself), such information is useful.

And if you have time to incident meter, you probably have time to look
at the histogram and adjust accordingly, as well.
Anonymous
March 25, 2005 2:50:12 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

McLeod wrote:
> On Fri, 25 Mar 2005 08:25:09 -0500, Alan Browne
> <alan.browne@freelunchVideotron.ca> wrote:
>
>
>>For those who use an incident meter or seperate spot meters (including
>>myself), such information is useful.
>
>
> And if you have time to incident meter, you probably have time to look
> at the histogram and adjust accordingly, as well.

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

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.
Anonymous
March 25, 2005 3:13:42 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

On 25 Mar 2005 10:54:52 GMT, Roland Karlsson
<roland_dot_karlsson@bonetmail.com> wrote:

>"Pete D" <no@email.com> wrote in
>news:MdO0e.11056$C7.1258@news-server.bigpond.net.au:
>
>> 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

Okay, but whether it be by table or experience, if you find your
camera to consistently meter under or over, you'd just adjust the
exposure accordingly wouldn't you?

....annoying if you switch between brands all the time, but for a
single DSLR body owner, no biggie.

And the report (or Alan) missed another significant angle here:

The D70 they used, is it the same as my D70? What's the consistency of
metering within each model like? If it's bad for any particular model,
their table becomes fairly irrelevant.

--
Owamanga!
http://www.pbase.com/owamanga
Anonymous
March 25, 2005 3:13:43 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Owamanga wrote:

> The D70 they used, is it the same as my D70? What's the consistency of
> metering within each model like? If it's bad for any particular model,
> their table becomes fairly irrelevant.

They don't mention if they're using samples of one or more.

If one were talking about lens variations (sharpness) I would agree.
But metering in electronic cameras and shutter speeds have become quite
precise and consistent over the past 10+ years.

--
-- 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.
Anonymous
March 25, 2005 5:30:16 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne wrote:
[]
> er, this is an equipment group. This *is* one of the things we
> discuss here.

"This" is cross-posted, so it's not even one group.....

David
Anonymous
March 25, 2005 5:30:17 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

David J Taylor wrote:

> Alan Browne wrote:
> []
>
>>er, this is an equipment group. This *is* one of the things we
>>discuss here.
>
>
> "This" is cross-posted, so it's not even one group.....

Both groups are equipment related. I apologize for my use of the
singular above and trust that the flogging, while justly deserved, will
be administered mercifully.

--
-- 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.
Anonymous
March 25, 2005 6:40:27 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 213jh$iuf$2
@inews.gazeta.pl:

> er, this is an equipment group. This *is* one of the things we discuss
> here.

Alan - I just tried to be nice to Pete.

Personally I fully agree with you. I just acknowledged
that not everyone do. And that is OK IMHO.


/Roland
Anonymous
March 25, 2005 6:40:28 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 213jh$iuf$2
> @inews.gazeta.pl:
>
>
>>er, this is an equipment group. This *is* one of the things we discuss
>>here.
>
>
> Alan - I just tried to be nice to Pete.
>
> Personally I fully agree with you. I just acknowledged
> that not everyone do. And that is OK IMHO.

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

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.
Anonymous
March 25, 2005 7:24:11 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Alan Browne wrote:
> David J Taylor wrote:
>
>> Alan Browne wrote:
>> []
>>
>>> er, this is an equipment group. This *is* one of the things we
>>> discuss here.
>>
>>
>> "This" is cross-posted, so it's not even one group.....
>
> Both groups are equipment related. I apologize for my use of the
> singular above and trust that the flogging, while justly deserved,
> will be administered mercifully.

As DSLRs are in the title, I thought you might have preferred the
slr-systems group.

I will not treat you to a flogging, sorry!

Cheers,
David
Anonymous
March 25, 2005 10:50:29 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 21cm6$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? :) 


/Roland
Anonymous
March 25, 2005 10:50:30 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 21cm6$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.


--
-- 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.
Anonymous
March 25, 2005 11:02:14 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

On Thu, 24 Mar 2005 23:02:51 -0500, Alan Browne
<alan.browne@freelunchVideotron.ca> wrote:

>Alan Browne wrote:
>
>> I picked up Casseur D'Images (No. 271, March 2005) and among other
> Chasseur D'Images

No need for correction. It was much more fun as it read first.

Jan Böhme
Korrekta personuppgifter är att betrakta som journalistik.
Felaktigheter utgör naturligtvis skönlitteratur.
Anonymous
March 25, 2005 11:02:15 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Jan Böhme wrote:

> On Thu, 24 Mar 2005 23:02:51 -0500, Alan Browne
> <alan.browne@freelunchVideotron.ca> wrote:
>
>
>>Alan Browne wrote:
>>
>>
>>>I picked up Casseur D'Images (No. 271, March 2005) and among other
>>
>> Chasseur D'Images
>
>
> No need for correction. It was much more fun as it read first.

I laughed myself, but explaining it didn't seem seemly.
Anonymous
March 25, 2005 11:42:27 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
<alan.browne@freelunchVideotron.ca> 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.
March 26, 2005 12:28:03 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote in message
news:D 21fg2$b6k$1@inews.gazeta.pl...
> McLeod wrote:
> > On Fri, 25 Mar 2005 08:25:09 -0500, Alan Browne
> > <alan.browne@freelunchVideotron.ca> wrote:
> >
> >
> >>For those who use an incident meter or seperate spot meters (including
> >>myself), such information is useful.
> >
> >
> > And if you have time to incident meter, you probably have time to look
> > at the histogram and adjust accordingly, as well.
>
> Quicker to set strobes with an incident flash meter. Though I am
> developing a worrisome, guilt inducing chimping habit when outdoors with
> the D7.
That is about the only way to set them correctly. I alas have no experience
with studio equipment.

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.

Jim
>
> 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.
Anonymous
March 26, 2005 12:28:04 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

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

--
-- 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.
Anonymous
March 26, 2005 1:42:43 AM

Archived from groups: rec.photo.digital (More info?)

"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
> Pete D wrote:
>
> > And as has been said before, it does not matter one tiny little jot as
long
> > as the photos come out right.
>
> For those who use an incident meter or seperate spot meters (including
> myself), such information is useful.

Not really. You have to calibrate your meter against the histograms that
result in your camera.

And I suspect that the results are simply random, since presumably they used
matrix/evaluative metering which is, in principle, completely random and
unpredictable (assuming it does what they say it does<g>).

David J. Littleboy
Tokyo, Japan
Anonymous
March 26, 2005 1:42:44 AM

Archived from groups: rec.photo.digital (More info?)

On Fri, 25 Mar 2005 22:42:43 +0900, "David J. Littleboy"
<davidjl@gol.com> wrote:

>
>"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
>> Pete D wrote:
>>
>> > And as has been said before, it does not matter one tiny little jot as
>long
>> > as the photos come out right.
>>
>> For those who use an incident meter or seperate spot meters (including
>> myself), such information is useful.
>
>Not really. You have to calibrate your meter against the histograms that
>result in your camera.
>
>And I suspect that the results are simply random, since presumably they used
>matrix/evaluative metering which is, in principle, completely random and
>unpredictable (assuming it does what they say it does<g>).

So, the database of 30,000 images is a big lie, it's just a
pseudo-random number generator.

That actually explains a lot.

I've done some tests with the D70, if my daughter (caucasian), pulls
her face to make her eyes to look more asian, the matrix metering is a
lot more accurate. I guess she suddenly matches some of the faces in
the database.

<g>

--
Owamanga!
http://www.pbase.com/owamanga
Anonymous
March 26, 2005 1:42:44 AM

Archived from groups: rec.photo.digital (More info?)

In article <d214ef$cs3$1@nnrp.gol.com>,
David J. Littleboy <davidjl@gol.com> wrote:
>"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
>> For those who use an incident meter or seperate spot meters (including
>> myself), such information is useful.
>
>Not really. You have to calibrate your meter against the histograms that
>result in your camera.
>
>And I suspect that the results are simply random, since presumably they used
>matrix/evaluative metering which is, in principle, completely random and
>unpredictable (assuming it does what they say it does<g>).

What does the sensitivity of a sensor have to do with the built-in lightmeter
of a camera?


--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency
Anonymous
March 26, 2005 1:42:45 AM

Archived from groups: rec.photo.digital (More info?)

On Fri, 25 Mar 2005 15:20:24 +0100, philip@pch.home.cs.vu.nl (Philip
Homburg) wrote:

>In article <d214ef$cs3$1@nnrp.gol.com>,
>David J. Littleboy <davidjl@gol.com> wrote:
>>"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
>>> For those who use an incident meter or seperate spot meters (including
>>> myself), such information is useful.
>>
>>Not really. You have to calibrate your meter against the histograms that
>>result in your camera.
>>
>>And I suspect that the results are simply random, since presumably they used
>>matrix/evaluative metering which is, in principle, completely random and
>>unpredictable (assuming it does what they say it does<g>).
>
>What does the sensitivity of a sensor have to do with the built-in lightmeter
>of a camera?

Are you talking histograms here? One assumes the manufacturer is
completely aware of the exact sensitivity of the sensor, and so takes
this into account when drawing the histogram.

So, compare external meter reading's suggestion of exposure values for
a given ISO to the resulting histogram at those same exposure values
to see if an adjustment to the meter's ISO setting is required to make
it 'accurate' for that sensor. Personally, I wouldn't trust my
interpretation of the histogram to not introduce yet another error
factor using this method.

--
Owamanga!
http://www.pbase.com/owamanga
Anonymous
March 26, 2005 1:42:46 AM

Archived from groups: rec.photo.digital (More info?)

In article <li8841hqhieugr3k37j6726vrdu41tmbjp@4ax.com>,
Owamanga <owamanga(not-this-bit)@hotmail.com> wrote:
>On Fri, 25 Mar 2005 15:20:24 +0100, philip@pch.home.cs.vu.nl (Philip
>Homburg) wrote:
>>What does the sensitivity of a sensor have to do with the built-in lightmeter
>>of a camera?
>
>Are you talking histograms here? One assumes the manufacturer is
>completely aware of the exact sensitivity of the sensor, and so takes
>this into account when drawing the histogram.

I think you can also show a histogram if you are completely unaware of
the effective sensitivity of the sensor.

The histogram is supposed to reflect the distribution of the RGB values
on an image. How the image was obtained is not revelevant for the histogram
(though the color space might be if you want to show brightness)


--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency
Anonymous
March 26, 2005 5:59:52 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <d202ab$rmr$1@inews.gazeta.pl>,
Alan Browne <alan.browne@freelunchVideotron.ca> 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 <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
March 26, 2005 6:10:16 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <Xns962479358D7AEklotjohan@130.133.1.4>,
Roland Karlsson <roland_dot_karlsson@bonetmail.com> wrote:

>"Pete D" <no@email.com> wrote in
>news:MdO0e.11056$C7.1258@news-server.bigpond.net.au:
>
>> 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 <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
March 26, 2005 6:14:08 AM

Archived from groups: rec.photo.digital (More info?)

In message <d214ef$cs3$1@nnrp.gol.com>,
"David J. Littleboy" <davidjl@gol.com> wrote:

>And I suspect that the results are simply random, since presumably they used
>matrix/evaluative metering which is, in principle, completely random and
>unpredictable (assuming it does what they say it does<g>).

Well, metering a white card or blank white wall should circumvent any
weighting algorithms. If the subject is a complex scene, then the
experiment is a complete joke.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
March 26, 2005 6:16:26 AM

Archived from groups: rec.photo.digital (More info?)

In message <dnc86h82qsi41g1ofof9qpj3p1@inews_id.stereo.hq.phicoh.net>,
philip@pch.home.cs.vu.nl (Philip Homburg) wrote:

>In article <d214ef$cs3$1@nnrp.gol.com>,
>David J. Littleboy <davidjl@gol.com> wrote:
>>"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
>>> For those who use an incident meter or seperate spot meters (including
>>> myself), such information is useful.
>>
>>Not really. You have to calibrate your meter against the histograms that
>>result in your camera.
>>
>>And I suspect that the results are simply random, since presumably they used
>>matrix/evaluative metering which is, in principle, completely random and
>>unpredictable (assuming it does what they say it does<g>).
>
>What does the sensitivity of a sensor have to do with the built-in lightmeter
>of a camera?

Exactly. This is not film, where one instance of a film in one camera
requires the same exact exposure in another camera; each digital "film"
is unique, and "proper exposure" is not necessarily the best exposure,
even if based on average grey rather than "exposing to the right".
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
March 26, 2005 10:31:34 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Fri, 25 Mar 2005 20:42:27 -0500, McLeod <cerveza@xplornet.com>
wrote:

>On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
><alan.browne@freelunchVideotron.ca> 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
Anonymous
March 26, 2005 11:04:18 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Sat, 26 Mar 2005 07:31:34 -0500, Glenn <gward1nospam@rogers.com>
wrote:

>chimping ?
>
>Pllease explain.

Photographer hunched over the back of his camera looking at the lcd
going "Oooo! oooo!"
Anonymous
March 26, 2005 11:30:08 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

McLeod wrote:

> On Fri, 25 Mar 2005 11:50:12 -0500, Alan Browne
> <alan.browne@freelunchVideotron.ca> 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.

--
-- 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.
Anonymous
March 26, 2005 12:01:40 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

JPS@no.komm 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.
Anonymous
March 26, 2005 3:36:00 PM

Archived from groups: rec.photo.digital (More info?)

<JPS@no.komm> wrote in message
news:eqk941h0e74trbk83e4ucv8tesh07olhiv@4ax.com...
> In message <dnc86h82qsi41g1ofof9qpj3p1@inews_id.stereo.hq.phicoh.net>,
> philip@pch.home.cs.vu.nl (Philip Homburg) wrote:
>
> >In article <d214ef$cs3$1@nnrp.gol.com>,
> >David J. Littleboy <davidjl@gol.com> wrote:
> >>"Alan Browne" <alan.browne@freelunchVideotron.ca> wrote:
> >>> For those who use an incident meter or seperate spot meters (including
> >>> myself), such information is useful.
> >>
> >>Not really. You have to calibrate your meter against the histograms that
> >>result in your camera.
> >>
> >>And I suspect that the results are simply random, since presumably they
used
> >>matrix/evaluative metering which is, in principle, completely random and
> >>unpredictable (assuming it does what they say it does<g>).
> >
> >What does the sensitivity of a sensor have to do with the built-in
lightmeter
> >of a camera?
>
> Exactly. This is not film, where one instance of a film in one camera
> requires the same exact exposure in another camera; each digital "film"
> is unique, and "proper exposure" is not necessarily the best exposure,
> even if based on average grey rather than "exposing to the right".

My guess would be that ISO is well-defined (something on the order of
spotmeter an 18%gray card and set that exposure, and the peak in the
histogram will be at exactly some well-defined place) and that the camera
mfrs adjust the amplifiers prior to A/D conversion to be exactly in line
with industry-standard definitions. It's pretty hard to imagine ISO meaning
anything else...

And that what the in-camera meter does is what the article was testing.

David J. Littleboy
Tokyo, Japan
Anonymous
March 26, 2005 3:36:01 PM

Archived from groups: rec.photo.digital (More info?)

In article <d22l93$qbf$2@nnrp.gol.com>,
David J. Littleboy <davidjl@gol.com> wrote:
>My guess would be that ISO is well-defined (something on the order of
>spotmeter an 18%gray card and set that exposure, and the peak in the
>histogram will be at exactly some well-defined place) and that the camera
>mfrs adjust the amplifiers prior to A/D conversion to be exactly in line
>with industry-standard definitions. It's pretty hard to imagine ISO meaning
>anything else...

I think the problem with ISO is that it works very well with systems that
can capture a limited dynamic range (say 5 stops) but not so good when you
want to capture 10 stops.

For a film that can handle 5 stops, you simply take the point where the
second derivative of the sensitivity curve is zero, call that 18% grey,
lookup the amount of light that generates that density in a table to find
the ISO value.

For a sensor, if you want a low ISO value, you can start at the point where
the sensor is saturated, go down 2.5 stops and convert the amount of light
to an ISO value. Problem is 1) most cameras have some extra head room
and 2) most people want to know the highest ISO not the lowest.

For high ISO values, you start at the noise floor, add some number of stops
and call that 18% grey. The problem here is the question of what an
acceptable level of noise is, and how many stops you add.

I think it would be nice if there could be some kind of two dimensional system
where both the noise floor and the saturation point are listed.


--
That was it. Done. The faulty Monk was turned out into the desert where it
could believe what it liked, including the idea that it had been hard done
by. It was allowed to keep its horse, since horses were so cheap to make.
-- Douglas Adams in Dirk Gently's Holistic Detective Agency
Anonymous
March 26, 2005 5:37:54 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 23q03$r5d$1
@inews.gazeta.pl:

> 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.

OK - then sorry - they are wrong.
ISO sensitivity is not defined by 118 in the converted JPEG.


/Roland
Anonymous
March 26, 2005 5:37:55 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 23q03$r5d$1
> @inews.gazeta.pl:
>
>
>>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.
>
>
> OK - then sorry - they are wrong.
> ISO sensitivity is not defined by 118 in the converted JPEG.

Go buy the magazine where, as I state above, the entire process is
detailed, 'blow by blow' including references to the standards, and
which I'm not going to type for you here.

And yes, mid tone is, as previously discussed, R=118=G=B.

--
-- 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.
Anonymous
March 26, 2005 5:37:55 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 23q03$r5d$1
> @inews.gazeta.pl:
>
>
>>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.
>
>
> OK - then sorry - they are wrong.
> ISO sensitivity is not defined by 118 in the converted JPEG.


I just repeated the test as follows:

0. Shot grey card at f/5.6 using strobe set at f/5.6 incident metered
(for ISO 100) with K-M 7D.

1. RAW import of the same shot.

2. In RAW import (Adobe) set all sliders to 0; temp to 5500K.

3. Within the RAW import, 8-bit end of R,G,B = 119,117,105 (typical,
many values around there with the blue being consistently 10 or 12
levels below the R and G. (Whether this is a reflection <npi> of the
card or the sensors is not determined).

4. Imported that into E 3.0. R,G,B values are the same.

5. Converted to 8-bit and saved as JPG

6. Reopened. Values are as above.

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.
Anonymous
March 26, 2005 8:25:19 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In rec.photo.digital Owamanga <owamanga(not-this-bit)@hotmail.com> wrote:
>
> Okay, but whether it be by table or experience, if you find your
> camera to consistently meter under or over, you'd just adjust the
> exposure accordingly wouldn't you?
>
> ...annoying if you switch between brands all the time, but for a
> single DSLR body owner, no biggie.
>
> And the report (or Alan) missed another significant angle here:
>
> The D70 they used, is it the same as my D70? What's the consistency of
> metering within each model like? If it's bad for any particular model,
> their table becomes fairly irrelevant.

If the D70 varies in sensitivity per individual camera then the D70
would be irrelavent. In fact, I am sure that they are consistant
between cameras and as such, it this is all useful information to have.
I own the D70 and will likely be working with film (Nikon N80) in the
not too distant future and it will be useful to know that my experience
with ISO settings on the D70 are likely to require a factor of 0.8 when
going to film.
Anonymous
March 26, 2005 8:25:20 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Thomas T. Veldhouse wrote:

>
> If the D70 varies in sensitivity per individual camera then the D70
> would be irrelavent. In fact, I am sure that they are consistant
> between cameras and as such, it this is all useful information to have.
> I own the D70 and will likely be working with film (Nikon N80) in the
> not too distant future and it will be useful to know that my experience
> with ISO settings on the D70 are likely to require a factor of 0.8 when
> going to film.

....then there's the meters...

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.
Anonymous
March 26, 2005 8:42:11 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 23t8b$8m1$1
@inews.gazeta.pl:

> And yes, mid tone is, as previously discussed, R=118=G=B.

Hmmm ... how can that be? The sensitivity of a sensor
is defined by the saturation level.

The conversion to JPEG depends on color space and the
bias you use for representing 255. So - the mid tone
can (IMHO) be anything in the JPEG.

Moreover - the R, G and B are only equal if the system
is in perfct color balance. And that is highly unlikely.


/Roland
Anonymous
March 26, 2005 8:42:12 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson wrote:

> Alan Browne <alan.browne@freelunchVideotron.ca> wrote in news:D 23t8b$8m1$1
> @inews.gazeta.pl:
>
>
>>And yes, mid tone is, as previously discussed, R=118=G=B.
>
>
> Hmmm ... how can that be? The sensitivity of a sensor
> is defined by the saturation level.
>
> The conversion to JPEG depends on color space and the
> bias you use for representing 255. So - the mid tone
> can (IMHO) be anything in the JPEG.
>
> Moreover - the R, G and B are only equal if the system
> is in perfct color balance. And that is highly unlikely.

We've gone through this before. As the parameter being tested is
fidelity to the ISO setting, the mid tone is the only place the can be
measured. The toe and shoulder should vary too much between camera
models to be of any use in comparison.

As my own test shows, the three are not in perfect balance, and one
should not expect or hope that they would be. Further, and as
mentioned, and again I suggest you get a copy of the mag, the ISO table
they published and that I repeated are rounded numbers.

Cheers
Alan

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.
Anonymous
March 26, 2005 8:53:06 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Alan Browne <alan.browne@freelunchVideotron.ca> wrote in
news:D 240n8$kpm$1@inews.gazeta.pl:

> I just repeated the test as follows:

Hmmm ... I assure you ... I am not trying to be difficult.
But ... I have a hard time to believe in this. I have added
some comments below.

> 0. Shot grey card at f/5.6 using strobe set at f/5.6 incident metered
> (for ISO 100) with K-M 7D.
>
> 1. RAW import of the same shot.
>
> 2. In RAW import (Adobe) set all sliders to 0; temp to 5500K.
>
> 3. Within the RAW import, 8-bit end of R,G,B = 119,117,105 (typical,
> many values around there with the blue being consistently 10 or 12
> levels below the R and G. (Whether this is a reflection <npi> of the
> card or the sensors is not determined).

I am sorry - I don't understand this at all.

> 4. Imported that into E 3.0. R,G,B values are the same.

Nor do I understand this. This might be because I have
no knowledge about Adobe RAW import. It looks like step
3 and 4 makes some modifications of the RAW data upon import.
How can we use the data for meassurements then? The data shold
be unaltered IMHO.

> 5. Converted to 8-bit and saved as JPG

Converting to 8 bit can be made in lots of ways. gamma?
color space? bias? This is another step where the data
is modified and therefore makes meassuremets invalid IMHO.

> 6. Reopened. Values are as above.

To mee it looks like the correct method is to compare
the level of white clipping and then use the definition
for ISO sensitivity for sensors.

How the image looks after converting with Adobe RAW to
JPEG seems totally bogus to me. If you don't want to
test the workflow described above of course. But most
serious photographers do not convert to JPEG.

>
> Cheers,
> Alan
>
Anonymous
March 26, 2005 9:12:46 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Roland Karlsson <roland_dot_karlsson@bonetmail.com> wrote in
news:Xns9625C01553423klotjohan@130.133.1.4:

> To mee it looks like the correct method is to compare
> the level of white clipping and then use the definition
> for ISO sensitivity for sensors.

Hmmm .. after some thought I withdraw this suggestion.
The clipping level might be hard to find.

The problem is even more complex really. There are two
different things you can meassure.

1. Given a standard luminosity of the picture - what
exposure time and aperture do the camera choose.

2. Given a standard luminosity of the picture - what
is the exposure on the CCD with a given exposure
time and aperture.

Case 1 meassures the light meassuring bias in the camera.

Case 2 meassures the light sensitivity of the system.

Both are two interesting results. But they are different.


/Roland
Anonymous
March 26, 2005 10:46:07 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Joe Makowiec <makowiec@invalid.invalid> wrote:

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

I've been wondering if checking the histogram is considered 'chimping'.
Is it OK if I just forgo the 'Ooh, ooh" part?
Anonymous
March 27, 2005 12:28:56 AM

Archived from groups: rec.photo.digital (More info?)

"Philip Homburg" <philip@pch.home.cs.vu.nl> wrote:
> David J. Littleboy <davidjl@gol.com> wrote:
> >My guess would be that ISO is well-defined (something on the order of
> >spotmeter an 18%gray card and set that exposure, and the peak in the
> >histogram will be at exactly some well-defined place) and that the camera
> >mfrs adjust the amplifiers prior to A/D conversion to be exactly in line
> >with industry-standard definitions. It's pretty hard to imagine ISO
meaning
> >anything else...
>
> I think the problem with ISO is that it works very well with systems that
> can capture a limited dynamic range (say 5 stops) but not so good when you
> want to capture 10 stops.

My understanding is that there's an ISO standard for dcam ISO speeds. I
might be wrong.

When I took a shot of a gray card with my 300D in manual mode set to the
exposure my Pentax spotmeter indicated, there was a peak in the histogram
suspiciously close to dead center.

> For a film that can handle 5 stops, you simply take the point where the
> second derivative of the sensitivity curve is zero, call that 18% grey,
> lookup the amount of light that generates that density in a table to find
> the ISO value.

For a lot of films, that's a fairly long region, not a point. But again, I'm
quite sure that the ISO has a very tight definition of what ISO speeds mean
for film.

> For a sensor, if you want a low ISO value, you can start at the point
where
> the sensor is saturated, go down 2.5 stops and convert the amount of light
> to an ISO value. Problem is 1) most cameras have some extra head room
> and 2) most people want to know the highest ISO not the lowest.
>
> For high ISO values, you start at the noise floor, add some number of
stops
> and call that 18% grey. The problem here is the question of what an
> acceptable level of noise is, and how many stops you add.

OK, this is getting silly. Go look up the damn ISO specs and tell us what
they say for both film and digital.

David J. Littleboy
Tokyo, Japan
!