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

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

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?

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

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.

On 2015-10-28 15:48, Alfred Molon wrote:
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.


Back when I bothered to read dpreview there was lots of mention on the
disparity of ISO sensitivity between camera makers or even cameras from
the same co.

Whether this is due to their interpretation of the method, sensor design
or optimization to make particular models stand out at a given ISO
number is anyone's guess.

And it is not at all important.

You can do a standard candle test, if you like. Shoot a grey card in
direct sunlight. Should give you a sunny-16 exposure. Deviance from
that represents "error". That said, the variance in grey cards that I
have spans a full stop or more...

What is important is testing your camera in various lighting situations,
understanding its metering system and if you're a noise-peeper figuring
out what ISO is the quietest. (On my preferred camera that would be ISO
160).

In article , Alan Browne
says...
You can do a standard candle test, if you like. Shoot a grey card in
direct sunlight.

Well, the sun light strength may differ depending on the day of the year
and the geographical location.
--
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

On 2015-10-30 03:10, Alfred Molon wrote:
In article , Alan Browne
says...
You can do a standard candle test, if you like. Shoot a grey card in
direct sunlight.

Well, the sun light strength may differ depending on the day of the year
and the geographical location.

That is true enough but it's also one of the sole independent tests you
can do absent a lab with the right equipment.

On Tue, 27 Oct 2015 20:07:15 +0100, 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?


Shoot a grey scale using sunny sixteen values, maybe.

On Tue, 27 Oct 2015 20:07:15 +0100, 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?


Borrow or rent an external light meter, compare the values. Then you
can have three variables.