How does ISO setting work?

(Ray Fischer) wrote in
:

NameHere wrote:

It doesn't increase noise per se, it only amplifies it

What a moron you are. Increasing noise doesn't increase noise?!?

The higher ISO setting per se doesn't increase noise, except on some P&S
cameras, and there, only slightly. It's the lower exposure, due to the
metering for the higher ISO in auto-exposure modes, which increases noise,
relative to signal. In absolute terms, except for the aforementioned P&S
cameras, the highest ISOs on a camera add the least amount of absolute
noise (or the same, in some cases, like medium format designs) to a given
absolute exposure. The trade-off is that the higher ISOs have a lower
absolute threshold for clipping on most cameras.

(Ray Fischer) wrote in
:


Apparently you're not smart enough to realize that "amplify" and
"increase" are synonymous. But then stupid trolls never are very
smart.

In sme way they are the same, but in the way that most people will
understand them, "increase" is much more likley to lead to false
conclusions, such as a conclusion that dialing in a higher ISO in a manual
exposure increases noise - which is not true, except slightly, on some P&S
cameras.

John Sheehy wrote:
(Ray Fischer) wrote in
:

NameHere wrote:

It doesn't increase noise per se, it only amplifies it

What a moron you are. Increasing noise doesn't increase noise?!?

The higher ISO setting per se doesn't increase noise, except on some P&S
cameras, and there, only slightly.

Yes it does.

It's the lower exposure, due to the
metering for the higher ISO in auto-exposure modes, which increases noise,
relative to signal.

Inane quibbling.

--
Ray Fischer

Rich wrote:
NameHere wrote in

Damn, you blind and useless trolls never quit do you.



Why don't you pick one screename on the photo groups. Who are you hiding
from?


He's hiding from me.

And 88% of the rest of the readers in this NG.

--
john mcwilliams

Ray Fischer wrote:
John Sheehy wrote:
(Ray Fischer) wrote in
:

NameHere wrote:
It doesn't increase noise per se, it only amplifies it
What a moron you are. Increasing noise doesn't increase noise?!?
The higher ISO setting per se doesn't increase noise, except on some P&S
cameras, and there, only slightly.

Yes it does.

It's the lower exposure, due to the
metering for the higher ISO in auto-exposure modes, which increases noise,
relative to signal.

Inane quibbling.

Ray's confused, now attacking any one at all.
Stick to the trolls, Ray, or keep telling the pest he's a moron, as it's
really helping....

--
lsmft

John McWilliams wrote:
Ray Fischer wrote:
John Sheehy wrote:
(Ray Fischer) wrote in
:

NameHere wrote:
It doesn't increase noise per se, it only amplifies it
What a moron you are. Increasing noise doesn't increase noise?!?
The higher ISO setting per se doesn't increase noise, except on some P&S
cameras, and there, only slightly.

Yes it does.

It's the lower exposure, due to the
metering for the higher ISO in auto-exposure modes, which increases noise,
relative to signal.

Inane quibbling.

Ray's confused, now attacking any one at all.

Says the protector of trolls.

--
Ray Fischer

"John McWilliams" wrote in message
...
Ray Fischer wrote:
John Sheehy wrote:
(Ray Fischer) wrote in
:
NameHere wrote:
It doesn't increase noise per se, it only amplifies it
What a moron you are. Increasing noise doesn't increase noise?!?
The higher ISO setting per se doesn't increase noise, except on some P&S
cameras, and there, only slightly.

Yes it does.

It's the lower exposure, due to the metering for the higher ISO in
auto-exposure modes, which increases noise, relative to signal.

Inane quibbling.

Ray's confused, now attacking any one at all.

But Ray's right here. Sure, if you don't mind throwing away two stops of
highlights, ISO 400 will have lower noise. But that's a complete snore since
you can't do photography with two less stops of highlights. So it really is
exactly and only inane quibbling.

It's like the argument that the 5D2 doesn't turn one's Canon wide angles
into unusable crap. Sure, images from the 17-40 and old 24TSE will be
marginally better on the 5D2 than on the 5D. But you didn't buy a 21MP
camera to take 12MP images, and at 21MP, the CA and mush will be a problem
in the larger prints you are trying to make.

--
David J. Littleboy
Tokyo, Japan

"David" wrote in message
...
I know relatively little about the technical workings of digital
photography, and from what I have read here, some of you know a great deal.

I would like to understand what happens in my camera when I change the ISO
setting.

Going to a higher ISO increases amplification of the image, making it
"brighter" so that higher shutter speeds and/or smaller apertures can be
used. It is often necessary to go to a higher ISO in poor light.


I am hoping that once I understand that, I will know the (potential)
disadvantages of always shooting at high ISO, if there are any.

Image noise increases at high ISO. At some point this may make the picture
unacceptably grainy, depending on what you consider acceptable. Most people
prefer to use the lowest ISO practicable, for best image quality and
definition. There may be "artistic" reasons to do otherwise, of course.


Yes, I am aware that some shots can benefit from blurred motion (streams &
waterfalls), and a smaller lens aperture can yield greater dept of field.
But are there other factors, such as noise, that change when I shoot at
ISO 3200 rather than ISO 400?

Definitely, ISO 3200 would produce more noise than ISO 400.

On Sun, 07 Mar 2010 18:30:08 -0800, John McWilliams
wrote:

Rich wrote:
NameHere wrote in

Damn, you blind and useless trolls never quit do you.



Why don't you pick one screename on the photo groups. Who are you hiding
from?


He's hiding from me.

And 88% of the rest of the readers in this NG.

OH yes, the world revolves around you. EVERYONE IS OUT TO GET YOU!

LOL!

"David J. Littleboy" wrote in message
...

"John McWilliams" wrote in message
...
Ray Fischer wrote:
John Sheehy wrote:
(Ray Fischer) wrote in
:
NameHere wrote:
It doesn't increase noise per se, it only amplifies it
What a moron you are. Increasing noise doesn't increase noise?!?
The higher ISO setting per se doesn't increase noise, except on some
P&S cameras, and there, only slightly.

Yes it does.

It's the lower exposure, due to the metering for the higher ISO in
auto-exposure modes, which increases noise, relative to signal.

Inane quibbling.

Ray's confused, now attacking any one at all.

But Ray's right here. Sure, if you don't mind throwing away two stops of
highlights, ISO 400 will have lower noise. But that's a complete snore
since you can't do photography with two less stops of highlights. So it
really is exactly and only inane quibbling.
[]
--
David J. Littleboy
Tokyo, Japan

Both Ray and John Sheehy are right.

- at a given brightness [i.e. count] level in the output image, if the ISO
is increased, less exposure is needed to reach that level, and less
exposure means a lower signal-to-noise ratio.

- with a given input light level and exposure [i.e. number of photons],
increasing the ISO does not [nominally] change the signal-to-noise ratio,
but does alter the out brightness [count].

David