Why no ISO 100 ??

Agreed, bro!


On 7/3/08 4:21 PM, in article ,
"Jake" wrote:

Or marketing cr*p.

For me, in the DSLR market, I will only trust Canon, because their products
do exactly what they say on the tin. The only exception to this would be
Nikon.


"Frank ess" wrote in message
...

My guess it the OP wants to trade of ISO "speed" for less noise. Someone
will be able to tell him the technical reason this is a neat-o plan but
doesn't always work.

A practical example is the Panasonic Lumix LX1. It has an ISO 80 setting,
and I always use it, but with too little light it produces noisy images,
just like the 100 setting, only not quite.

Yeah, on the Kodachrome 25 and 15 (?). Some real potential there, in the
right circumstances. Must be a reason they are no longer part of the
photographer's repertoire.

"simon steel" wrote in message
...
Ok...
Higher ISO means more noise - we all know that...

But why don't cameras come with an ISO lower than 100?
Is there some trade off in image quality below the benchmark ISO100
figure?

not all of us want higher shutter speeds... some of us would like to slow
down the the shutter speeds..

SS

Some do, my Fujifilm S5700 goes down to ISO64.
Regards Mike.

simon steel wrote:
My guess it the OP wants to trade of ISO "speed" for less noise.

I actually would like to shoot slower speeds without need for
filters... Had not realised that noise would also be an issue with
sub-100 ISO setting.
Was really just curious as to why the min speeds in my DSLRs are 100
and 200 [Pentax K10D and istDL]

ss

Simon,

It's as Doug said - the sensor will saturate when fed too much light, so
get use lower speeds you need an ND filter. You /could/ make a less
sensitive sensor, with ISO 25 as its lowest speed, but then its highest
usable ISO would be proportionately reduced, and the camera would be less
attractive to many....

David

In article , David J
Taylor says...

It's as Doug said - the sensor will saturate when fed too much light, so
get use lower speeds you need an ND filter. You /could/ make a less
sensitive sensor, with ISO 25 as its lowest speed, but then its highest
usable ISO would be proportionately reduced, and the camera would be less
attractive to many....

They could make a multiple exposure sensor, i.e. a sensor exposing four
times the image and averaging the images. Would give lower noise and an
ISO equivalent to 25 (4 x the exposure time).
--

Alfred Molon
------------------------------
Olympus 50X0, 8080, E3X0, E4X0, E5X0 and E3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site

Alfred Molon wrote:
In article , David J
Taylor says...

It's as Doug said - the sensor will saturate when fed too much
light, so get use lower speeds you need an ND filter. You /could/
make a less sensitive sensor, with ISO 25 as its lowest speed, but
then its highest usable ISO would be proportionately reduced, and
the camera would be less attractive to many....

They could make a multiple exposure sensor, i.e. a sensor exposing
four times the image and averaging the images. Would give lower noise
and an ISO equivalent to 25 (4 x the exposure time).

We had a discussion about this possibility recently - in connection with
capturing specular highlight details.

Cheers,
David

"simon steel" wrote in
:

Ok...
Higher ISO means more noise - we all know that...

That's not true at all. On a given camera, with all images metered for 0
EC at the respective ISOs, there will be more noise in the highlights and
midtones at higher ISOs, but in the shadows, even on the same camera in
some cases, the read noise may be slightly lower at the next higher ISO,
in 1/3-stop increments (all current Canon DSLRs besides the rebels have
this characteristic).

Comparing two different cameras, a higher ISO on one may have less noise
than a lower one on another, even with the same size sensor.

But why don't cameras come with an ISO lower than 100?
Is there some trade off in image quality below the benchmark ISO100
figure?

not all of us want higher shutter speeds... some of us would like to
slow down the the shutter speeds..

When cameras have low base ISOs, it is usually because of two factors:

1) There is less highlight headroom (it's a pull, relatively speaking) -
this is true of many digital backs and P&S cameras. DSLRs are usually
rated for a stop more headroom than those.

2) The camera just isn't very sensitive. A camera that starts at a
higher ISO will generally have less noise at any given ISO than a camera
that starts at lower ISO.

Cameras that start at low ISOs generally have an implicit neutral density
effect permanently stuck in the camera.

Now, future technologies may actually create lower ISOs that fill the
photosites with photons more than once, and that will bring low ISOs
without compromise to high ISOs.

Best way now is to just take multiple exposures and add them together.
Ironically, this will yield less noise in the shadows than a true low-ISO
would. The only problem is that you will have blackout between
exposures, if there are any trails in the image.

--


John P Sheehy

"dwight" wrote in
:

My Canon S3IS also has an 80 ISO, but I rarely use it other than a
bright sunny day. And I don't care for the results at either ISO400 or
800, so I'm pretty much stuck at 100 or 200.

Good thing it has the IS...

.... and it makes the IS' job much simpler when some big, heavy mirror isn't
slapping around. Even without IS, I get sharper images at compromised
hand-held shutter speeds with my P&S cameras. I can shoot my FZ50 at ISO
100 with IS at 420mm EFL in a shady street and get tack-sharp pictures of
relatively stationary objects, with shutter speeds sometimes down to 1/30.
With my 30D, I'd have to use ISO 800 to 1600 with my 300mm IS, and get
about 1 - 1.6 stops stronger read noise in the shadows.

The slappin' mirror has got to go the way of the dinosaurs. It is
primitive BS.

--


John P Sheehy

John Sheehy wrote:
"dwight" wrote in
:

My Canon S3IS also has an 80 ISO, but I rarely use it other than a
bright sunny day. And I don't care for the results at either ISO400 or
800, so I'm pretty much stuck at 100 or 200.

Good thing it has the IS...

... and it makes the IS' job much simpler when some big, heavy mirror isn't
slapping around. Even without IS, I get sharper images at compromised
hand-held shutter speeds with my P&S cameras. I can shoot my FZ50 at ISO
100 with IS at 420mm EFL in a shady street and get tack-sharp pictures of
relatively stationary objects, with shutter speeds sometimes down to 1/30.
With my 30D, I'd have to use ISO 800 to 1600 with my 300mm IS, and get
about 1 - 1.6 stops stronger read noise in the shadows.

The slappin' mirror has got to go the way of the dinosaurs. It is
primitive BS.

IIRC the EOS-1v has a "mirror catcher" that avoids slap by controlling
the mirror landing actively thus eliminating most of the shock. This
could be re-implemented on the higher end Canon's. (and other manufs).

Another approach (at the cost of a stop) would be a "pelicule" mirror,
which given Canons great noise performance would easily be worth working
at 1 stop higher ISO (while also bringing the shutter lag down to the
5ms region like the EOS-1e pelicule. (v. 40 - 50ms for most high end
DSLR's).

--
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Alan Browne wrote in
:

The reality is that most sensors in the "35mm" class have a natural
sensitivity somewhere between 100 and 200. (Which is why many of the
Sony based Nikon's all start at 200).

Well, I don't think they really warrant 200 per se, but for some stupid
reason, manufacturers like to have the base ISO as 50*(2^n), so since the
sensors can't do 100 with a repectable highlight headroom in the RAW data,
they make 200 the base "normal" ISO, but the camera might really be ISO 130
to 160 or 180, and they treat 160 as a weird ISO, when in fact it, or 140,
or whatever, should be the base ISO. They're not doing anyone any favors,
except the people who like to compare cameras at specific ISOs. Many
cameras could have more useful DR and SNR curves if the cameras started at
an ISO that digitized almost full-well capacity (with real gain, at the
critical points in the signal path).


--


John P Sheehy

George Kerby wrote in
:

Some cameras are superior: My Canon EOS-1 Ds Mark II has the option to
go to ISO 50. Nikon most likely hasn't.

When a digital camera of existing technology has base ISO that is low, it
is not a quality feature. The mk2 series have low quantum efficiency, IOW,
many photons that hit the sensor surface never get captured; that is one
reason why the camera can have a base ISO of 50.

This is not the same as with film, which is slower when the grain is finer,
and takes more exposure to get the chemical reaction.

The "read noise floor" is closer to saturation in Canons with ISO 50 at 50,
compared to 100. All you get is a bit less shot noise (which there is not
much of, anyway), and many of the shots can be taken at ISO 100 with
positive EC, anyway, for less read noise.

--


John P Sheehy