How to measure ISO
 

I have two cameras. At the same ISO, aperture and exposure time one
takes brighter images than the other one.

How to measure the real ISO values at which the cameras took the
pictures?
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

How to measure ISO
 

On 2015-10-27 19:07:15 +0000, Alfred Molon said:

I have two cameras. At the same ISO, aperture and exposure time one
takes brighter images than the other one.

What are the sensor differences?

How to measure the real ISO values at which the cameras took the
pictures?


--
Regards,

Savageduck

How to measure ISO
 

On 27/10/2015 19:07, Alfred Molon wrote:
I have two cameras. At the same ISO, aperture and exposure time one
takes brighter images than the other one.

How to measure the real ISO values at which the cameras took the
pictures?


With my Fuji X-E1 I find I have to push exposure 2/3 stop to get
adequate shadow detail. I've found various Canon compacts to be fine.
This of course is for "average" scenes, others are likely to need
adjustment anyway.

I don't really see the relevance of ISO. Obviously, one or other cameras
(or both) don't meet the standard, but provided you have an exposure
adjustment dial it is just a question of learning your camera (given
that you probably have personal tastes in both subject matter and
presentation).

Or are you saying that you have a camera without such an adjustment, and
you are trying to demonstrate that it is faulty?

How to measure ISO
 

In article ,
newshound says...
Or are you saying that you have a camera without such an adjustment, and
you are trying to demonstrate that it is faulty?

I meant that these two cameras, if set at the same ISO value, aperture
and exposure time should deliver an image with the same brightness
value.
But one of the cameras creates a brighter image, even in RAW (if
applying the same RAW conversion parameters).

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

How to measure ISO
 

In article , Alfred
Molon wrote:

Or are you saying that you have a camera without such an adjustment, and
you are trying to demonstrate that it is faulty?

I meant that these two cameras, if set at the same ISO value, aperture
and exposure time should deliver an image with the same brightness
value.
But one of the cameras creates a brighter image, even in RAW (if
applying the same RAW conversion parameters).

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.

lots of cameras cheat.

How to measure ISO
 

In article ,
Whisky-dave wrote:
On Wednesday, 28 October 2015 20:05:09 UTC, nospam wrote:
In article , Alfred
Molon wrote:

Or are you saying that you have a camera without such an adjustment, and
you are trying to demonstrate that it is faulty?

I meant that these two cameras, if set at the same ISO value, aperture
and exposure time should deliver an image with the same brightness
value.
But one of the cameras creates a brighter image, even in RAW (if
applying the same RAW conversion parameters).

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.

lots of cameras cheat.

Is it a cheat or a lie ?

Neither, I think. As I understand it, the ISO standard
gives manufacturers some latitude to choose how they
want to set the ISO scale for each particular model. For
example, if the sensor's native sensitivity measures,
say 139, the manufacturer has the flexibility under the
ISO standard to call that ISO 100 or ISO 200, and then
adjust the metering to give the appropriate exposure values
for the 'adjusted' ISO.

It makes sense, I think, because people want to see ISOs
based on 100 rather than something like ISO 139. It does
however, make an awful lot of camera comparisons completely
bogus since the ISO adjustments are rarely taken into account.

-nan

How to measure ISO
 

In article , Nan
wrote:

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.

lots of cameras cheat.

Is it a cheat or a lie ?

Neither, I think. As I understand it, the ISO standard
gives manufacturers some latitude to choose how they
want to set the ISO scale for each particular model. For
example, if the sensor's native sensitivity measures,
say 139, the manufacturer has the flexibility under the
ISO standard to call that ISO 100 or ISO 200, and then
adjust the metering to give the appropriate exposure values
for the 'adjusted' ISO.

it's not about native iso, it's about what the camera does when set to
a specific iso, such as 100, 125, 160, 200, etc.

some cameras cheat. that's just how it is.

It makes sense, I think, because people want to see ISOs
based on 100 rather than something like ISO 139. It does
however, make an awful lot of camera comparisons completely
bogus since the ISO adjustments are rarely taken into account.

it doesn't invalidate anything. if iso 125 on a camera is really 160,
the exposure will be 1/3rd stop less and the end result will be
essentially the same.

How to measure ISO
 

nospam wrote:
In article , Nan
wrote:

In other words either the ISO 100 of one camera is in reality an ISO 80
or an ISO 125 and the other camera is accurate, or both cameras deviate
a bit from the ISO.

lots of cameras cheat.

Is it a cheat or a lie ?

Neither, I think. As I understand it, the ISO standard
gives manufacturers some latitude to choose how they
want to set the ISO scale for each particular model. For
example, if the sensor's native sensitivity measures,
say 139, the manufacturer has the flexibility under the
ISO standard to call that ISO 100 or ISO 200, and then
adjust the metering to give the appropriate exposure values
for the 'adjusted' ISO.

it's not about native iso, it's about what the camera does when set to
a specific iso, such as 100, 125, 160, 200, etc.

some cameras cheat. that's just how it is.

No cameras "cheat". The Standard basically says that any method
the manufacturer likes, is okay. That makes cheating not only
unnecessary, but virtually impossible.

And in fact it's a system that has turned out to work well
enough over the years!

--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)

How to measure ISO
 

In article , Floyd L. Davidson
wrote:

No cameras "cheat". The Standard basically says that any method
the manufacturer likes, is okay. That makes cheating not only
unnecessary, but virtually impossible.

then there is no standard.

And in fact it's a system that has turned out to work well
enough over the years!

clearly not.

if iso 100 on one camera is not the same as iso 100 on another camera
or the same as with film, then the number is meaningless.

How to measure ISO
 

nospam wrote:
In article , Floyd L. Davidson
wrote:

No cameras "cheat". The Standard basically says that any method
the manufacturer likes, is okay. That makes cheating not only
unnecessary, but virtually impossible.

then there is no standard.

And in fact it's a system that has turned out to work well
enough over the years!

clearly not.

if iso 100 on one camera is not the same as iso 100 on another camera
or the same as with film, then the number is meaningless.

Okay, it works well for everyone except you.

--
Floyd L. Davidson http://www.apaflo.com/
Ukpeagvik (Barrow, Alaska)