A Photography forum. PhotoBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » PhotoBanter.com forum » Digital Photography » Digital Photography
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

How to measure ISO



 
 
Thread Tools Display Modes
  #21  
Old October 30th 15, 05:02 AM posted to rec.photo.digital
nospam
external usenet poster
 
Posts: 22,123
Default How to measure ISO

In article , Tony Cooper
wrote:

Not a big problem, but the question is which camera has the correct ISO
setting, of if perhaps both cameras deviate from the true ISO 100.

While you may have a point, it would not affect me to know that the
ISO setting in my camera is 100 off or not. I know what I can expect
from a setting, and set the camera accordingly.


for one camera, perhaps, but that number may not be the same on other
cameras.


Trust you to argue by stating the bloody obvious.


trust you to go on another rant, and i'm not arguing.

If you routinely
use two different cameras, you would soon learn to know what the
result is for a particular setting.


maybe so, but if the iso was correct, that would not be needed.
  #22  
Old October 30th 15, 08:10 AM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,195
Default How to measure ISO

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
  #23  
Old October 30th 15, 02:12 PM posted to rec.photo.digital
Whiskers
external usenet poster
 
Posts: 188
Default How to measure ISO

On 2015-10-30, nospam wrote:
In article , Eric Stevens
wrote:

Not a big problem, but the question is which camera has the correct
ISO setting, of if perhaps both cameras deviate from the true ISO
100.

While you may have a point, it would not affect me to know that the
ISO setting in my camera is 100 off or not. I know what I can
expect from a setting, and set the camera accordingly.


Things worked just as well in the days I set my exposure to the
Weston scale. The numbers don't really matter but when you have more
than one camera its nice if they share a common scale.


exactly the point.


Using film, you could use the same batch of the same brand in all your
cameras - if you were worried enough about the actual 'speed' you'd
shoot a test strip for each batch of film to determine the best 'speed'
setting for that batch for you. You'd also be aware of differences
between the cameras and lenses - and adjust shutter and aperture
settings accordingly, or the film speed setting if the camera had its
own 'automatic' exposure meter.

Electronic sensors generally aren't interchanged between cameras, and
their performance is remarkably stable over time, but they do vary one
from another, and of course cameras and lenses still do so too. So
you'll get to know that 'this camera tends to blow the highlights' or
'this lens is a bit dark at short focal lengths' or 'the fast shutter
speeds tend to underexpose' and compensate to get the results you want.

ISO 'speed' ratings are guides rather than absolute measurements. For
electronic sensors there are at least three different methods of deciding
what the 'speed' of a sensor is, and all allow for some subjective
judgment. Wikipedia is a good place to start reading.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~
  #24  
Old October 30th 15, 05:06 PM posted to rec.photo.digital
nospam
external usenet poster
 
Posts: 22,123
Default How to measure ISO

In article ,
Whiskers wrote:

Not a big problem, but the question is which camera has the correct
ISO setting, of if perhaps both cameras deviate from the true ISO
100.

While you may have a point, it would not affect me to know that the
ISO setting in my camera is 100 off or not. I know what I can
expect from a setting, and set the camera accordingly.

Things worked just as well in the days I set my exposure to the
Weston scale. The numbers don't really matter but when you have more
than one camera its nice if they share a common scale.


exactly the point.


Using film, you could use the same batch of the same brand in all your
cameras - if you were worried enough about the actual 'speed' you'd
shoot a test strip for each batch of film to determine the best 'speed'
setting for that batch for you. You'd also be aware of differences
between the cameras and lenses - and adjust shutter and aperture
settings accordingly, or the film speed setting if the camera had its
own 'automatic' exposure meter.


one of the downsides of film is that every batch is different, one of
numerous flaws that digital solves.

because of that, many photographers bought film in large quantities so
that they could calibrate their workflow for one batch. they had to
freeze most of it so that it didn't expire before they had a chance to
use it. crazy!

they often took test shots, usually a macbeth chart or similar, so that
they could adjust the exposure and colour balance to match their
previous batch of film.

fortunately that insanity is no more, as digital is consistent shot to
shot for the life of the camera.

Electronic sensors generally aren't interchanged between cameras, and
their performance is remarkably stable over time, but they do vary one
from another, and of course cameras and lenses still do so too. So
you'll get to know that 'this camera tends to blow the highlights' or
'this lens is a bit dark at short focal lengths' or 'the fast shutter
speeds tend to underexpose' and compensate to get the results you want.


that's what having a standardized rating is supposed to solve.

ISO 'speed' ratings are guides rather than absolute measurements. For
electronic sensors there are at least three different methods of deciding
what the 'speed' of a sensor is, and all allow for some subjective
judgment. Wikipedia is a good place to start reading.


the fact that there's more than one way to measure it makes the rating
rather useless.

it's at best, a rough guide.
  #25  
Old October 30th 15, 08:52 PM posted to rec.photo.digital
Alan Browne
external usenet poster
 
Posts: 12,640
Default How to measure ISO

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.
  #26  
Old October 30th 15, 08:59 PM posted to rec.photo.digital
Alan Browne
external usenet poster
 
Posts: 12,640
Default How to measure ISO

On 2015-10-30 12:38, Whisky-dave wrote:
On Friday, 30 October 2015 16:06:15 UTC, nospam wrote:
In article
, Whiskers
wrote:

Not a big problem, but the question is which camera has
the correct ISO setting, of if perhaps both cameras
deviate from the true ISO 100.

While you may have a point, it would not affect me to know
that the ISO setting in my camera is 100 off or not. I
know what I can expect from a setting, and set the camera
accordingly.

Things worked just as well in the days I set my exposure to
the Weston scale. The numbers don't really matter but when
you have more than one camera its nice if they share a common
scale.

exactly the point.

Using film, you could use the same batch of the same brand in all
your cameras - if you were worried enough about the actual
'speed' you'd shoot a test strip for each batch of film to
determine the best 'speed' setting for that batch for you. You'd
also be aware of differences between the cameras and lenses - and
adjust shutter and aperture settings accordingly, or the film
speed setting if the camera had its own 'automatic' exposure
meter.


one of the downsides of film is that every batch is different, one
of numerous flaws that digital solves.


but batches of sensors are differnt too, which is whwere teh original
Q came from in that two cameras set set to ISO 100 should expose at
exactly the same level of brightness, but they don't.


If they're the same model camera I'd expect them to be too close for
casual measurement no matter what the batch. (Because I'd expect the
manufacturer to store calibration data on the sensor).

s
fortunately that insanity is no more, as digital is consistent shot
to shot for the life of the camera.


doesn't help if you have more than one camera though.


It's not so big a difference that you can't work them both. You have to
know your cameras well. This is the same across my Hasselblad lenses
.... on some the timer is a bit long (1/3 stop) which doesn't sound like
much unless shooting E-6.




Electronic sensors generally aren't interchanged between cameras,
and their performance is remarkably stable over time, but they do
vary one from another, and of course cameras and lenses still do
so too. So you'll get to know that 'this camera tends to blow
the highlights' or 'this lens is a bit dark at short focal
lengths' or 'the fast shutter speeds tend to underexpose' and
compensate to get the results you want.


that's what having a standardized rating is supposed to solve.


So hom come the OP was asking why his ISO one one camera is difernt
from teh other. You'd have thopugh with 10 bit minium resolution they
could get it right wouldn't you.


For a given model they should be too close for casual measure. And in a
precise test I'd assume far less than 1/3 stop.



ISO 'speed' ratings are guides rather than absolute measurements.
For electronic sensors there are at least three different methods
of deciding what the 'speed' of a sensor is, and all allow for
some subjective judgment. Wikipedia is a good place to start
reading.


the fact that there's more than one way to measure it makes the
rating rather useless.


So why have it ? Are you expecting the IOS to be measured at 5600k or
5400k or 3200k or anything else, or perhaps red, blue, green, or
yellow magenta or cyan light would be best. Moonlight might be OK too
for hi ISO.


The standard sets an objective. Engineers at each co. interpret it as
they see fit.





it's at best, a rough guide.


Yep. I remebr on boxes of film the sped was always given a s a guide
rathe rthan a dead cert, a bit like setting a gues make or temerature
on an oven. Yes I've even doen that and if I set my oven to 180C I
can get temeratures of 165-200.


Oven controllers are not very accurate - I agree with the range you show
there.


  #27  
Old October 30th 15, 09:25 PM posted to rec.photo.digital
nospam
external usenet poster
 
Posts: 22,123
Default How to measure ISO

In article ,
Whisky-dave wrote:

Not a big problem, but the question is which camera has the correct
ISO setting, of if perhaps both cameras deviate from the true ISO
100.

While you may have a point, it would not affect me to know that the
ISO setting in my camera is 100 off or not. I know what I can
expect from a setting, and set the camera accordingly.

Things worked just as well in the days I set my exposure to the
Weston scale. The numbers don't really matter but when you have more
than one camera its nice if they share a common scale.

exactly the point.

Using film, you could use the same batch of the same brand in all your
cameras - if you were worried enough about the actual 'speed' you'd
shoot a test strip for each batch of film to determine the best 'speed'
setting for that batch for you. You'd also be aware of differences
between the cameras and lenses - and adjust shutter and aperture
settings accordingly, or the film speed setting if the camera had its
own 'automatic' exposure meter.


one of the downsides of film is that every batch is different, one of
numerous flaws that digital solves.


but batches of sensors are differnt too, which is whwere teh original Q came
from in that two cameras set set to ISO 100 should expose at exactly the same
level of brightness, but they don't.


different cameras have different sensors.

two copies of the same camera will have the same sensor. you'd need lab
instruments to find *any* difference, and if there is one, it would be
much smaller than the manufacturing tolerances of the shutter and
aperture. in other words, it can be ignored.

because of that, many photographers bought film in large quantities so
that they could calibrate their workflow for one batch.


Some of that was to save money and always have film in stock.
I used to buy 50ft reels of HP3 , 100ft reels of HP4.
I still have the bulk film loader somewhere.

I'm not to sure that had such a thing as workflows then.


of course they did.

they had to
freeze most of it so that it didn't expire before they had a chance to
use it. crazy!


No most didn't freeze it they kept it cool in the fridge.


that depends how long they're going to keep it.

they often took test shots, usually a macbeth chart or similar, so that
they could adjust the exposure and colour balance to match their
previous batch of film.


didn't need to as each was done individually and looked at.
It was only when machines started bulk processing was that needed.


it absolutely was needed.

fortunately that insanity is no more, as digital is consistent shot to
shot for the life of the camera.


doesn't help if you have more than one camera though.


that's the whole point.

Electronic sensors generally aren't interchanged between cameras, and
their performance is remarkably stable over time, but they do vary one
from another, and of course cameras and lenses still do so too. So
you'll get to know that 'this camera tends to blow the highlights' or
'this lens is a bit dark at short focal lengths' or 'the fast shutter
speeds tend to underexpose' and compensate to get the results you want.


that's what having a standardized rating is supposed to solve.


So hom come the OP was asking why his ISO one one camera is difernt from teh
other. You'd have thopugh with 10 bit minium resolution they could get it
right wouldn't you.


because there's no standardized rating system.

ISO 'speed' ratings are guides rather than absolute measurements. For
electronic sensors there are at least three different methods of deciding
what the 'speed' of a sensor is, and all allow for some subjective
judgment. Wikipedia is a good place to start reading.


the fact that there's more than one way to measure it makes the rating
rather useless.


So why have it ?


good question.

Are you expecting the IOS to be measured at 5600k or 5400k or 3200k or
anything else, or perhaps red, blue, green, or yellow magenta or cyan light
would be best. Moonlight might be OK too for hi ISO.


it should be standardized.

it's at best, a rough guide.


Yep. I remebr on boxes of film the sped was always given a s a guide rathe
rthan a dead cert, a bit like setting a gues make or temerature on an oven.
Yes I've even doen that and if I set my oven to 180C I can get temeratures of
165-200.


that's because film is not as good as digital.

technology advances. film is obsolete.
  #28  
Old October 30th 15, 10:20 PM posted to rec.photo.digital
Me
external usenet poster
 
Posts: 470
Default How to measure ISO

On 28/10/2015 08:07, 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?

Sensorgen has some measured vs claimed ISO data.

Some examples at set ISO 3200, calculated ISO is:

EOS 7DII 2458
EOS 5DIII 2518
EOS 1DX 2423

D5300 2483
D750 2332
D810 2367

OMDEM5 1489
OMDEM10 1663

DMCGH2 2989
DMCGH4 1860

Phase One IQ180 990

A7R 2240
A7S 2627

The general trend seems to be that most overstate ISO by about 1/3 stop.
That's probably sensible (blown highlight protection).

Some are well over that 1/3 stop. Of course there's suspicion it's also
done to "cheat" - to make the cameras look better than they really are
in side by side high ISO comparisons.
  #29  
Old October 31st 15, 11:21 PM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,195
Default How to measure ISO

In article ,
Whisky-dave says...
fortunately that insanity is no more, as digital is consistent shot to
shot for the life of the camera.


doesn't help if you have more than one camera though.


The difference in ISO is actually not a problem, because the camera
automatically sets the exposure and in manual mode you can determine the
right exposure by judging the histogram.

I was just curious how ISO could be measured. Got some feedback, but
isn't there a scientific definition, e.g. "100 ISO is the camera
sensitivity for which at an illumunance of ... lux the camera chooses
an exposure of ..." - something like this.
--
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
  #30  
Old October 31st 15, 11:24 PM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,195
Default How to measure ISO

In article , Me says...
Some examples at set ISO 3200, calculated ISO is:

EOS 7DII 2458
EOS 5DIII 2518
EOS 1DX 2423

D5300 2483
D750 2332
D810 2367

OMDEM5 1489
OMDEM10 1663

DMCGH2 2989
DMCGH4 1860

Phase One IQ180 990

A7R 2240
A7S 2627


Hmmmm... isn't this cheating? Could be compared to the fuel consumption
and pollution output levels which car manufacturers declare and what
instead these values are in reality.
--
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
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can one measure colour temperature with the Nikon D3? Dave[_27_] Digital Photography 12 September 8th 08 06:01 PM
Can one measure colour temperature with the Nikon D3? Dave[_27_] 35mm Photo Equipment 12 September 8th 08 06:01 PM
Don't measure a film! Von Fourche 35mm Photo Equipment 0 June 27th 06 11:02 AM
5x4 - How to measure film /plate register ? Malcolm Stewart Large Format Photography Equipment 3 February 19th 05 02:07 AM
How to measure ink(toner) usage! AVPSoft Digital Photography 11 November 9th 04 11:09 PM


All times are GMT +1. The time now is 08:19 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright 2004-2018 PhotoBanter.com.
The comments are property of their posters.