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I see that the Olympus OM-D E-M5 doesn't have an ISO mode lower than
200. What does ISO really mean for a digital camera, though?

--
Please reply to: | "We establish no religion in this country, we
pciszek at panix dot com | command no worship, we mandate no belief, nor
Autoreply is disabled | will we ever. Church and state are, and must
| remain, separate." --Ronald Reagan, 10/26/1984

On Jun 7, 1:07*am, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:
> On 2012-06-06 18:35 , Paul Ciszek wrote:
>
> > I see that the Olympus OM-D E-M5 doesn't have an ISO mode lower than
> > 200. *What does ISO really mean for a digital camera, though?
>
> But it certainly has quite a bit above 200.
>
> First off it is part and parcel of the reciprocity equation that
> photographers use when trading between DOF, speed and image quality. *It
> used to be 2 degrees of freedom - now there are three (shutter speed,
> aperture and now ISO).

There was always 3 wasn;t there. I remmeber buying HP3 because it was
400 ASA/ISO
I wanted to photograph the stars so reciprocity was a slight concern
to me.
DOF wasn;t relivant but shutter speed was.

In the days of film a lower ASA/ISO meant finer grain and usually less
contrasty images.

Not sure how the modern DSLR is arrcted by setting a low ISO, btu I
still assume a lower
ISO setting is linked to better image quality than a higher ISO could
produce given the same conditions.

>
> The other important notion is: gain.
>
> The 'typical' or 'natural' ISO of most digital cameras is about 150 -
> 200. *So going below that means artificial compression of the dynamic range.
>
> Above that, at least for a bit, analog amplification, means no big loss
> in DR to increase the gain, but increasing noise. *But as the noise is
> constrained spatially (no big "grain blobs") it looks a lot better than
> high speed film.
>
> Later DSLR's are truly remarkable in the high ISO's achieved with little
> noise. *That means shooting in more difficult conditions where film was
> challenged while getting high quality images without needing a tripod.
> (Add in image stabilization and it's compounded by another 2 - 4 stops).
>
> When you run out of analog gain (why do they call them digital cameras
> anyway?) then digital gain is applied for the higher end.
>
> And as A/D depth increases the gains (so to speak) in ISO may rise some
> more.
>
> If you need "lower than 200" ISO you can get some very expensive digital
> cameras (Hasselblad comes to mind) or throw on an ND filter.
>
> I'm sure others will have more to add.
>
> --
> "Civilization is the limitless multiplication of unnecessary necessities."
> * * * * * * *-Samuel Clemens.

In article <oMWdnfvFd->,
Alan Browne <> wrote:
>
>And as A/D depth increases the gains (so to speak) in ISO may rise some
>more.
>
>If you need "lower than 200" ISO you can get some very expensive digital
>cameras (Hasselblad comes to mind) or throw on an ND filter.
>
>I'm sure others will have more to add.

Sigh. I've just been so conditioned to the idea that you *must* use
ISO 100 for bright, sunny outdoor photography. Heck, maybe I should
just set ISO to "Auto" and think of it no more.

--
Please reply to: | "We establish no religion in this country, we
pciszek at panix dot com | command no worship, we mandate no belief, nor
Autoreply is disabled | will we ever. Church and state are, and must
| remain, separate." --Ronald Reagan, 10/26/1984

Alan Browne <> wrote:

> The 'typical' or 'natural' ISO of most digital cameras is about 150 -
> 200. So going below that means artificial compression of the dynamic range.

Nikon, maybe. Canon, not so much.

-Wolfgang

Wolfgang Weisselberg <> wrote:
> Alan Browne <> wrote:

>> The 'typical' or 'natural' ISO of most digital cameras is about 150 -
>> 200. So going below that means artificial compression of the dynamic range.

> Nikon, maybe. Canon, not so much.

Depends on the specific sensor and how the camera maker has handled
the lowest ISOs in a particular camera. ISO 50 is often handled as
Alan suggests, being "bodged" in simply to give you more latitude in
shutter and aperture selection, but not in all cases. For example,
according to DXO's tests, the Sony A77 has it's top dynamic range and
least noise at ISO 50.

--
Chris Malcolm

Chris Malcolm <> wrote:
> Wolfgang Weisselberg <> wrote:
>> Alan Browne <> wrote:

>>> The 'typical' or 'natural' ISO of most digital cameras is about 150 -
>>> 200. So going below that means artificial compression of the dynamic range.

>> Nikon, maybe. Canon, not so much.

> Depends on the specific sensor and how the camera maker has handled
> the lowest ISOs in a particular camera. ISO 50 is often handled as
> Alan suggests, being "bodged" in simply to give you more latitude in
> shutter and aperture selection, but not in all cases. For example,
> according to DXO's tests, the Sony A77 has it's top dynamic range and
> least noise at ISO 50.

Canon usually has the native ISO between 50 and 100, as in "50
does cost dynamic range in the highlights (and is therefore an
extended ISO setting" and "100 doesn't". Which sorta bites
the "150-200" claim.

Nikon, AFAIK, usually start their normal range at 200 ... so
there the claim may work out.

-Wolfgang

Wolfgang Weisselberg <> wrote:
> Chris Malcolm <> wrote:
>> Wolfgang Weisselberg <> wrote:
>>> Alan Browne <> wrote:

>>>> The 'typical' or 'natural' ISO of most digital cameras is about 150 -
>>>> 200. So going below that means artificial compression of the dynamic range.

>>> Nikon, maybe. Canon, not so much.

>> Depends on the specific sensor and how the camera maker has handled
>> the lowest ISOs in a particular camera. ISO 50 is often handled as
>> Alan suggests, being "bodged" in simply to give you more latitude in
>> shutter and aperture selection, but not in all cases. For example,
>> according to DXO's tests, the Sony A77 has it's top dynamic range and
>> least noise at ISO 50.

> Canon usually has the native ISO between 50 and 100, as in "50
> does cost dynamic range in the highlights (and is therefore an
> extended ISO setting" and "100 doesn't". Which sorta bites
> the "150-200" claim.

> Nikon, AFAIK, usually start their normal range at 200 ... so
> there the claim may work out.

The Sony R1 had its base ISO at 160, which was where it was at its
best. The next up was 200, then 400, etc..

I get the impression the camera makers know what the best ISO for
their sensor is, but they also know the howls of protest and confusion
and ignorant criticism and salesdriod superstition that would
inevitably follow releasing a camera with a base ISO of say 87 or
163. So they simply stick to the old film-based ISO steps so as not to
alarm the collective brain of the market.

--
Chris Malcolm