10D ISO ratings a lie?

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?

How are you making the comparison?
What are you "metering"?

If you're using sunny 16, then you shouldn't be metering at all.
Are you metering from a grey card?
If so, there are a number of factors that can throw this off somewhat.

What flat, "grey" surface are you referring to?
18% grey card?
What?

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?

How are you making the comparison?
What are you "metering"?

If you're using sunny 16, then you shouldn't be metering at all.
Are you metering from a grey card?
If so, there are a number of factors that can throw this off somewhat.

What flat, "grey" surface are you referring to?
18% grey card?
What?

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?

How are you making the comparison?
What are you "metering"?

If you're using sunny 16, then you shouldn't be metering at all.
Are you metering from a grey card?
If so, there are a number of factors that can throw this off somewhat.

What flat, "grey" surface are you referring to?
18% grey card?
What?

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?

I just went outside and tried mine at 1:00PM under bright sunlight, and
little to no haze.
It did indeed turn into a "Sunny 11" before it exposed properly.
Clearly under-exposed on my 10D.

The under-exposure was shot at 1/90th, f16, ISO 100.

My conclusion is based upon photoshop histograms, camera histograms, and
visual inspection on my properly calibrated monitor.

It does seem to be significantly under-sensitive in this case.

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?

I just went outside and tried mine at 1:00PM under bright sunlight, and
little to no haze.
It did indeed turn into a "Sunny 11" before it exposed properly.
Clearly under-exposed on my 10D.

The under-exposure was shot at 1/90th, f16, ISO 100.

My conclusion is based upon photoshop histograms, camera histograms, and
visual inspection on my properly calibrated monitor.

It does seem to be significantly under-sensitive in this case.

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?

I just went outside and tried mine at 1:00PM under bright sunlight, and
little to no haze.
It did indeed turn into a "Sunny 11" before it exposed properly.
Clearly under-exposed on my 10D.

The under-exposure was shot at 1/90th, f16, ISO 100.

My conclusion is based upon photoshop histograms, camera histograms, and
visual inspection on my properly calibrated monitor.

It does seem to be significantly under-sensitive in this case.

In message ,
"E. Magnuson" wrote:

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")

To tell you the truth, I really don't have much confidence in Phil
Askey's precision. He may have pushed this in software, or he may have
wrote the wrong values in the article.

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

I'm not sure you understand my discovery. What I'm saying is that the
ISO values that the camera claims it is using may actually be
exaggerated by over 2x.

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.

I am not drawing from one sample. I have suspected this for a long
time, and I finally tested it today. The sun was high and unobstructed
by clouds; I set the camera to ISO 100, manual mode, f16, and 1/100. I
took a picture from my window of the parking lot below, where the trees
and the cars were in direct sunlight, and the only thing in the top half
of the histogram was a bright white car. I tried again later with two
other lenses, and they all gave the same exposure for the same subject
areas. I took one shot with each of three lenses of the same scene, and
only bright white objects were in the top half of the histogram, and the
images were equally dark. As I said in the original post, I checked my
Sekonic L-558 meter, and the camera exposed at 1/60 (f16, Av mode) where
the Sekonic said 1/125. After I did this I remember that images I took
with the Sekonic and with sunny f16 in the past were always dark.

The camera's firmware *definitely* knows that the camera is actually a
lower ISO than it says, because auto-exposure never gives me these dark
images in sunlight.
--


John P Sheehy

In message ,
"E. Magnuson" wrote:

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")

To tell you the truth, I really don't have much confidence in Phil
Askey's precision. He may have pushed this in software, or he may have
wrote the wrong values in the article.

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

I'm not sure you understand my discovery. What I'm saying is that the
ISO values that the camera claims it is using may actually be
exaggerated by over 2x.

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.

I am not drawing from one sample. I have suspected this for a long
time, and I finally tested it today. The sun was high and unobstructed
by clouds; I set the camera to ISO 100, manual mode, f16, and 1/100. I
took a picture from my window of the parking lot below, where the trees
and the cars were in direct sunlight, and the only thing in the top half
of the histogram was a bright white car. I tried again later with two
other lenses, and they all gave the same exposure for the same subject
areas. I took one shot with each of three lenses of the same scene, and
only bright white objects were in the top half of the histogram, and the
images were equally dark. As I said in the original post, I checked my
Sekonic L-558 meter, and the camera exposed at 1/60 (f16, Av mode) where
the Sekonic said 1/125. After I did this I remember that images I took
with the Sekonic and with sunny f16 in the past were always dark.

The camera's firmware *definitely* knows that the camera is actually a
lower ISO than it says, because auto-exposure never gives me these dark
images in sunlight.
--


John P Sheehy

In message ,
"E. Magnuson" wrote:

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")

To tell you the truth, I really don't have much confidence in Phil
Askey's precision. He may have pushed this in software, or he may have
wrote the wrong values in the article.

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

I'm not sure you understand my discovery. What I'm saying is that the
ISO values that the camera claims it is using may actually be
exaggerated by over 2x.

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.

I am not drawing from one sample. I have suspected this for a long
time, and I finally tested it today. The sun was high and unobstructed
by clouds; I set the camera to ISO 100, manual mode, f16, and 1/100. I
took a picture from my window of the parking lot below, where the trees
and the cars were in direct sunlight, and the only thing in the top half
of the histogram was a bright white car. I tried again later with two
other lenses, and they all gave the same exposure for the same subject
areas. I took one shot with each of three lenses of the same scene, and
only bright white objects were in the top half of the histogram, and the
images were equally dark. As I said in the original post, I checked my
Sekonic L-558 meter, and the camera exposed at 1/60 (f16, Av mode) where
the Sekonic said 1/125. After I did this I remember that images I took
with the Sekonic and with sunny f16 in the past were always dark.

The camera's firmware *definitely* knows that the camera is actually a
lower ISO than it says, because auto-exposure never gives me these dark
images in sunlight.
--


John P Sheehy

In message f9TOc.12966$8G6.1906@fed1read04,
"Mark M" wrote:

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?

How are you making the comparison?

There is no "the" comparison.
I mentioned more than one comparison.

In one, I'm comparing sunny f16 exposures to automatic exposure. Sunny
f16 images taken in direct sunlight (with distinct shadows) are much
darker than auto-exposed images. A clean white car in direct sunlight
is inside the histogram with about a stop to spare. The rest of the
image is in the left half of the histogram.


What are you "metering"?

In another comparison, in Av mode, the 10D wants over double the
exposure that my Sekonic meter suggests is necessary, when pointed at
pure blue sky, or a blank white wall.

If you're using sunny 16, then you shouldn't be metering at all.

I wasn't metering the sunny f16 images. I took shots with various
lenses, at ISO 100, 1/100 and f16 of directly sunlit scenes.

Are you metering from a grey card?

Not this time, but I do remember in the past getting a dark grey card
after metering it with the Sekonic.

If so, there are a number of factors that can throw this off somewhat.

No relevance here. Doesn't matter if it is black, white, grey, glossy,
or matte. I'm comparing a Sekonic exposure meter to the one in the
camera, with the same flat surface with narrow histogram.

What flat, "grey" surface are you referring to?
18% grey card?
What?

Blank white wall. Doesn't really matter, as long as it is illuminated
evenly. I was comparing the camera's metering to the Sekonic's to
*verify* that my sunny f16 episode was not a fluke.

--


John P Sheehy