10D ISO ratings a lie?

Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

When I do, the pictures are under-exposed by over a stop. When I check
exposure of a flat, grey surface or blue sky in the camera, and compare
it to my Sekonic meter, there is about 1.3 stops difference.

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

--


John P Sheehy

wrote in message
...
Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

When I do, the pictures are under-exposed by over a stop. When I check
exposure of a flat, grey surface or blue sky in the camera, and compare
it to my Sekonic meter, there is about 1.3 stops difference.

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

--


John P Sheehy

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

--
Skip Middleton
http://www.shadowcatcherimagery.com

wrote in message
...
Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

When I do, the pictures are under-exposed by over a stop. When I check
exposure of a flat, grey surface or blue sky in the camera, and compare
it to my Sekonic meter, there is about 1.3 stops difference.

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

--


John P Sheehy

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

--
Skip Middleton
http://www.shadowcatcherimagery.com

wrote in message
...
Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

When I do, the pictures are under-exposed by over a stop. When I check
exposure of a flat, grey surface or blue sky in the camera, and compare
it to my Sekonic meter, there is about 1.3 stops difference.

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

--


John P Sheehy

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

--
Skip Middleton
http://www.shadowcatcherimagery.com

In message i4SOc.3316$go.2741@fed1read07,
"Skip M" wrote:

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

The "problem" I refer to should not be affected by the camera's metering
at all. There is no metering involved at all in shooting in manual mode
with "sunny f16" settings, and no relation to your auto-exposure or
metering anomalies. Taking the camera's stated ISO literally, there is
about 5 stops of highlight headroom in the red channel RAW data, and 4.5
stops in the green and blue channels.

My camera's metering is pretty good (as far as filling the histogram is
concerned), even autoflash (unless I'm close to the subject and using a
high ISO and better beamer, in which case it may wash out). But if what
I say is universal, then the camera is actually working at ISO 320 or so
when it says 800.

--


John P Sheehy

In message i4SOc.3316$go.2741@fed1read07,
"Skip M" wrote:

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

The "problem" I refer to should not be affected by the camera's metering
at all. There is no metering involved at all in shooting in manual mode
with "sunny f16" settings, and no relation to your auto-exposure or
metering anomalies. Taking the camera's stated ISO literally, there is
about 5 stops of highlight headroom in the red channel RAW data, and 4.5
stops in the green and blue channels.

My camera's metering is pretty good (as far as filling the histogram is
concerned), even autoflash (unless I'm close to the subject and using a
high ISO and better beamer, in which case it may wash out). But if what
I say is universal, then the camera is actually working at ISO 320 or so
when it says 800.

--


John P Sheehy

In message i4SOc.3316$go.2741@fed1read07,
"Skip M" wrote:

Hmm, you may have a point about "low noise." But our 10D is about 1/3 stop
over by its own meter, as it is, and about 1 1/3 over on flash, metered by
our Sekonic. I'll check the daylight readings when it gets home. The
combination of ours and yours sounds like a consistency problem, at least...

The "problem" I refer to should not be affected by the camera's metering
at all. There is no metering involved at all in shooting in manual mode
with "sunny f16" settings, and no relation to your auto-exposure or
metering anomalies. Taking the camera's stated ISO literally, there is
about 5 stops of highlight headroom in the red channel RAW data, and 4.5
stops in the green and blue channels.

My camera's metering is pretty good (as far as filling the histogram is
concerned), even autoflash (unless I'm close to the subject and using a
high ISO and better beamer, in which case it may wash out). But if what
I say is universal, then the camera is actually working at ISO 320 or so
when it says 800.

--


John P Sheehy

On 2004-07-31, wrote:

Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

Well if you look at
http://www.dpreview.com/reviews/canoneos10d/page20.asp, You'll see
that Phil's exposure here is bascially Sunny F16 (Well, F11 @ 1/200)
Do you think that these images are underexposed by a stop? Could be
slightly underexposed, but the day looks a bit hazy to me (the shadows
are less distinct than I like for "Sunny")

Actually, the conventional wisdom is the opposite: that the Canon
10D and 300D are actually a little more sensitive than the ISO
indicates at least compared to other DSLRs:

1/2 stop over the D70 here at all ISOs:
http://www.dpreview.com/reviews/nikond70/page14.asp

1/3rd when Sunny and outdoors
http://www.dpreview.com/reviews/nikond70/page21.asp

and 2/3 stop 10D over the SD10 he
http://www.dpreview.com/reviews/sigmasd10/page13.asp

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

Not until you eliminate other sources of error. It could be your
camera. It could be your lens. You also don't say how the images are
processed or how you are actually measuring the camera exposure. You
should not draw a sweeping conclusion from one sample.

--
Erik

On 2004-07-31, wrote:

Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

Well if you look at
http://www.dpreview.com/reviews/canoneos10d/page20.asp, You'll see
that Phil's exposure here is bascially Sunny F16 (Well, F11 @ 1/200)
Do you think that these images are underexposed by a stop? Could be
slightly underexposed, but the day looks a bit hazy to me (the shadows
are less distinct than I like for "Sunny")

Actually, the conventional wisdom is the opposite: that the Canon
10D and 300D are actually a little more sensitive than the ISO
indicates at least compared to other DSLRs:

1/2 stop over the D70 here at all ISOs:
http://www.dpreview.com/reviews/nikond70/page14.asp

1/3rd when Sunny and outdoors
http://www.dpreview.com/reviews/nikond70/page21.asp

and 2/3 stop 10D over the SD10 he
http://www.dpreview.com/reviews/sigmasd10/page13.asp

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

Not until you eliminate other sources of error. It could be your
camera. It could be your lens. You also don't say how the images are
processed or how you are actually measuring the camera exposure. You
should not draw a sweeping conclusion from one sample.

--
Erik

On 2004-07-31, wrote:

Has anyone tried using "Sunny f16" in manual mode with a 10D on a sunny
day?

Well if you look at
http://www.dpreview.com/reviews/canoneos10d/page20.asp, You'll see
that Phil's exposure here is bascially Sunny F16 (Well, F11 @ 1/200)
Do you think that these images are underexposed by a stop? Could be
slightly underexposed, but the day looks a bit hazy to me (the shadows
are less distinct than I like for "Sunny")

Actually, the conventional wisdom is the opposite: that the Canon
10D and 300D are actually a little more sensitive than the ISO
indicates at least compared to other DSLRs:

1/2 stop over the D70 here at all ISOs:
http://www.dpreview.com/reviews/nikond70/page14.asp

1/3rd when Sunny and outdoors
http://www.dpreview.com/reviews/nikond70/page21.asp

and 2/3 stop 10D over the SD10 he
http://www.dpreview.com/reviews/sigmasd10/page13.asp

This casts a shadow on the integrity of the camera's "low noise at high
ISO", when ISO 800 is really ISO 320, no?

Not until you eliminate other sources of error. It could be your
camera. It could be your lens. You also don't say how the images are
processed or how you are actually measuring the camera exposure. You
should not draw a sweeping conclusion from one sample.

--
Erik