Meaning of ISO value in digital photography?
 

In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...n--photo-11963

Meaning of ISO value in digital photography?
 

On 6/14/2018 1:48 PM, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...n--photo-11963


I am going to try to give you a simplified, non-technical explanation.
As with most generalities it is not 100% technically accurate, but
should serve as a guideline.
ISO is a measurement of the light sensitivity of the sensor. Digital ISO
is adjustable in many cameras. And yes, it is a matter of adjusting the
amplification. If you are using a wider lens opening, and slower shutter
speed, you will be able to use a lower ISO.
Digital noise is one of the undesired artifacts in the image. Higher ISO
will result in more digital noise, and lessor image quality. Many of the
newer high quality sensors are designed to work at a higher ISO, with
less noticeable noise, and reduction in image quality.
There are some of us here who do not object to noise, while others have
serious objections. The point at which noise becomes objectionable often
comes down to a matter of taste and personal preferences.

HTH

BTW: I will not get involved in a war over technicalities. There may be
some who will nitpick my simplified explanation. If you have a specific
question, i will be happy to either answer it, or give you a reference.

--
PeterN

Meaning of ISO value in digital photography?
 

In article , Jim-P
wrote:

In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

it's the same with digital cameras, except that higher iso has more
noise.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

it does not.

like film, the sensitivity of a sensor is fixed.

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

yep, and with amplification comes additional noise, just as faster
films were more grainy.

Meaning of ISO value in digital photography?
 

On Jun 14, 2018, Jim-P wrote
(in et):

In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

Correct. The important thing is not to conflate analog ISO ratings with
digital ratings. They are two different things.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

Any given sensor will have a base sensitivety, or ISO. Typically ISO 200, or
ISO 100 depending on manufacturer. The sensitivety does not change in the
same way that analog film emulsions can be changed. Any increase from the
base ISO is an increase of signal gain, or amplification of the signal from
the sensor.

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

What you are doing when increasing the ISO number with a digital camera is
increasing the signal gain between the sensor and the camera CPU. This is
effectively the same as turning up the volume (gain) on an audio amplifier.
As gain increases so does amplified noise. How the noise manifests itself
depends on the sensor, the CPU, and the SNR of the pair. That is why some
cameras have better high ISO performance than others.

By using ISO to rate the base sensor sensitivity, and any increases by upping
the gain just gives folks who have made the move from film to digital a rough
guide by referencing film ISO.

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...n--photo-11963

That article is spelling out the fact that digital ISO is not the equivalent
of analoge ISO.

--

Regards,
Savageduck

Meaning of ISO value in digital photography?
 

On 2018-06-14 19:48, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

Yes, the analog amplifier before the analog to digital converter changes
its gain. Like the volume control in a radio.

Cameras may also add digital multiplication at the end of the range.
This means that values can go 10, 10, 20... skipping intermediate
values. Or even more noise.

--
Cheers, Carlos.

Meaning of ISO value in digital photography?
 

In article , PeterN says...
BTW: I will not get involved in a war over technicalities. There may be
some who will nitpick my simplified explanation.

Have you considered putting that nitpicker into your killfilter?
--
Alfred Molon

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

Meaning of ISO value in digital photography?
 

On Thu, 14 Jun 2018 14:26:40 -0400, PeterN wrote:

On 6/14/2018 1:48 PM, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...n--photo-11963


I am going to try to give you a simplified, non-technical explanation.
As with most generalities it is not 100% technically accurate, but
should serve as a guideline.
ISO is a measurement of the light sensitivity of the sensor. Digital ISO
is adjustable in many cameras. And yes, it is a matter of adjusting the
amplification. If you are using a wider lens opening, and slower shutter
speed, you will be able to use a lower ISO.
Digital noise is one of the undesired artifacts in the image. Higher ISO
will result in more digital noise, and lessor image quality. Many of the
newer high quality sensors are designed to work at a higher ISO, with
less noticeable noise, and reduction in image quality.
There are some of us here who do not object to noise, while others have
serious objections. The point at which noise becomes objectionable often
comes down to a matter of taste and personal preferences.

Thanks. This makes me wonder what ISO I should set, if I don't leave it on
auto.

Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?

Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?

Meaning of ISO value in digital photography?
 

On Jun 14, 2018, Jim-P wrote
(in article ):

On Thu, 14 Jun 2018 14:26:40 -0400, PeterN wrote:

On 6/14/2018 1:48 PM, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...ical-explorati
on--photo-11963

I am going to try to give you a simplified, non-technical explanation.
As with most generalities it is not 100% technically accurate, but
should serve as a guideline.
ISO is a measurement of the light sensitivity of the sensor. Digital ISO
is adjustable in many cameras. And yes, it is a matter of adjusting the
amplification. If you are using a wider lens opening, and slower shutter
speed, you will be able to use a lower ISO.
Digital noise is one of the undesired artifacts in the image. Higher ISO
will result in more digital noise, and lessor image quality. Many of the
newer high quality sensors are designed to work at a higher ISO, with
less noticeable noise, and reduction in image quality.
There are some of us here who do not object to noise, while others have
serious objections. The point at which noise becomes objectionable often
comes down to a matter of taste and personal preferences.

Thanks. This makes me wonder what ISO I should set, if I don't leave it on auto.

Let us start by asking, what camera are you using?

As far as which ISO you should use you should consider the light environment
of the scene you are trying to capture, along with your interpretation of
that scene, all balanced to achieve an acceptable exposure.

Auto ISO can work, but you are going to be better off if you have an
understanding of the exposure triangle and photography in general. It might
be time for you to read a book on photography.

Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?

Close enough.

Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?

In a digital camera the ISO settings are going to be a close approximation of
ISO values of film, and are more guidelines rather than exact figures. For
example, you are going to find it difficult to dig up ISO 51200 film, but
there are digital cameras capable of producing acceptable images with ISO
that high.

--

Regards,
Savageduck

Meaning of ISO value in digital photography?
 

In article , Jim-P
wrote:

This makes me wonder what ISO I should set, if I don't leave it on
auto.

generally, lower iso is better and auto-iso is best left on, except for
specific situations where you want a particular iso.

however, you will want to set a maximum upper bound for auto-iso so it
doesn't raise it higher than what you consider acceptable quality.

if your camera does not have such a limit (not all do) then auto-iso
can potentially result in very noisy photos, but the alternative is no
photo or very blurry photos due to camera shake (very slow shutter
speed).

Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?

no. digital noise is for all intents, not noticeable until you get to
around 1600-3200 (assuming an slr class camera). for cameras with
smaller sensors, noise becomes a problem earlier.

film grain at iso 400 was acceptable, tolerable at 1600 and beyond
that, too grainy to be used other than unusual scenarios.

in other words, digital will produce vastly better quality at the same
iso.

Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?

quite different in that digital is better in every way.

Meaning of ISO value in digital photography?
 

On 06/14/2018 08:05 PM, Savageduck wrote:
On Jun 14, 2018, Jim-P wrote
(in article ):

On Thu, 14 Jun 2018 14:26:40 -0400, PeterN wrote:

On 6/14/2018 1:48 PM, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.

In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?

So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?

I tried to understand this page but it got far too technical....

https://photography.tutsplus.com/art...ical-explorati
on--photo-11963

I am going to try to give you a simplified, non-technical explanation.
As with most generalities it is not 100% technically accurate, but
should serve as a guideline.
ISO is a measurement of the light sensitivity of the sensor. Digital ISO
is adjustable in many cameras. And yes, it is a matter of adjusting the
amplification. If you are using a wider lens opening, and slower shutter
speed, you will be able to use a lower ISO.
Digital noise is one of the undesired artifacts in the image. Higher ISO
will result in more digital noise, and lessor image quality. Many of the
newer high quality sensors are designed to work at a higher ISO, with
less noticeable noise, and reduction in image quality.
There are some of us here who do not object to noise, while others have
serious objections. The point at which noise becomes objectionable often
comes down to a matter of taste and personal preferences.

Thanks. This makes me wonder what ISO I should set, if I don't leave it on auto.

In the film days, we used the "Sunny-16" rule: Set the shutter speed
equal to the ISO (then "ASA"). In bright sunshine, use f/16. Slightly
cloudy- use f/11, open shade- f/8, full shade- f/5.6. This technique
would usually give a good exposure.

Combine that with the "focal length equals shutter speed" rule: The
longer the focal length, the faster the shutter speed to give acceptable
hand-held images. For a 200mm lens, you use a shutter speed of 1/250
second.

Example: 100mm lens calls for 1/100 second minimum. Set the ISO also at
100, and use the "Sunny-16" rule. Then refer to SD's exposure triangle,
three paragraphs down...

Let us start by asking, what camera are you using?

As far as which ISO you should use you should consider the light environment
of the scene you are trying to capture, along with your interpretation of
that scene, all balanced to achieve an acceptable exposure.

Auto ISO can work, but you are going to be better off if you have an
understanding of the exposure triangle and photography in general. It might
be time for you to read a book on photography.

f/stop, shutter speed, and ISO.

With a higher ISO, you can use a faster shutter speed and smaller lens
aperture. You get better motion stopping and depth of field, but you
also get grain (or noise).
With a lower ISO, you need to either use a slower shutter speed or a
wider aperture. You get better "grain", but you lose motion-stopping or
depth of field.
It's all a trade-off.

Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?

Close enough.

I'm going to have to respectfully disagree with SD here, but just on his
two word paragraph.

The "grain" of a digital sensor would be relative to the pixel count of
that sensor. To go to the extreme, a 3K-pixel toy camera would have a
"grainy" image no matter how low you dial the ISO- assuming that such a
camera would have that feature! OTOH, a 48M-pixel medium format digital
back would have a very tight "grain" pattern, exceeding that of 35mm ISO
200 film.


Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?

In a digital camera the ISO settings are going to be a close approximation of
ISO values of film, and are more guidelines rather than exact figures.

In fact, there will _some_ variation in the ISO between manufacturers of
film, and the emulsion batches. Which is why many pros would buy large
quantities of film, and shoot a few test rolls before shooting work for
pay.

For
example, you are going to find it difficult to dig up ISO 51200 film, but
there are digital cameras capable of producing acceptable images with ISO
that high.



--
Ken Hart