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lowest iso speed?

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Anonymous
August 10, 2005 12:45:26 AM

Archived from groups: rec.photo.digital (More info?)

My Canon 10D iso only goes down to iso 100. I am curious if other digital
SLRs can go below that, since film cameras can use eg iso 25 film (like
Kodachrome 25). And if not, why can't digital go below iso 100?

More about : lowest iso speed

Anonymous
August 10, 2005 12:45:27 AM

Archived from groups: rec.photo.digital (More info?)

>Proteus writes ...
>
>And if not, why can't digital go below iso 100?

Gisle's post explains this well, I think.

>My Canon 10D iso only goes down to iso 100. I am curious if other
>digital SLRs can go below that

My 1D MII has an expansion mode that lets you shoot at 50 for exposure
purposes even though it's not really better than 100. We use it often
when we need an extra stop, typically for blurring things. Here are a
few semi-abstract images my wife took last week at f/32, iso 50 and
with a pol filter (which slows it down another 1-2 stops) to slow the
shutter speed as we were driving home from a trip in mid-day light as
examples of when you might find a lower ASA handy ...
http://members.aol.com/bhilton665/blurs/vla_88.jpg
http://members.aol.com/bhilton665/blurs/bridge_354.jpg
http://members.aol.com/bhilton665/blurs/dunno_926.jpg
http://members.aol.com/bhilton665/blurs/trees_342.jpg
http://members.aol.com/bhilton665/blurs/burn_245.jpg

Bill
Anonymous
August 10, 2005 2:27:50 AM

Archived from groups: rec.photo.digital (More info?)

On Tue, 09 Aug 2005 20:45:26 -0500, Proteus wrote:

> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

I don't know how accurate this information is, coming from
mini-reviews in a UK camera magazine, and that ISO 6 seems like it
would be a typo, where it may have been intended to be ISO 60.

1. Kodak DCS PRO SLR/n: ISO 80 to 600

2. Kodak DCS PRO SLR/c: ISO 6 to 800 (fully calibrated) and ISO 1000
to 1600 (extended mode).

As for why digital SLRs don't go below 100, consider where lower
ISOs would be used. In very bright light. The sensor already be on
the verge of blowing highlights if the exposure isn't restricted.
If the ISO was reduced the camera would compensate by changing the
exposure (longer shutter speed and/or wider aperture) while
lessening the sensor's amplification. But that would result in a
sensor already near overflowing with photons (each sensor pixel site
has a limit to the number of photons it can accept) trying to
capture perhaps 2 or 4 times more photons. This would probably
result in much greater areas of blown highlights. There is a much
better method to simulate a lower ISO - use an ND filter. :) 

Note: I just saw Gisle's reply which said:

> I guess it would be possible to design a sensor with ISO 25 as
> its baseline sensitivity - but as this probably would make it
> very noisy at higher ISO levels, such a sensor would have a
> very limited appeal.

That's a good evaluation of Kodak's DCS PRO SLRs :) 
Related resources
Anonymous
August 10, 2005 3:55:35 AM

Archived from groups: rec.photo.digital (More info?)

Proteus wrote:

> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

I used to have a Canon Pro90IS. It was 2MP camera with a 10X image
stabilized zoom lens.

It did ISO 50, 100, 200 and 400.
Anonymous
August 10, 2005 4:40:02 AM

Archived from groups: rec.photo.digital (More info?)

I've got a Canon A95 P&S which has a min ISO of 50 - but my 20D, like
the 10D, has a floor of 100. I've not really noticed any particular
hinderance to having a minimum of 100 on my DSLR, but then, different
photographers will want different things I guess.
Anonymous
August 10, 2005 6:29:58 AM

Archived from groups: rec.photo.digital (More info?)

8 on Kodak DSLR line.

=bob=

"Proteus" <nospam@nowhere.net> wrote in message
news:A%cKe.14064$Tt6.4424@fe04.lga...
> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?
>
Anonymous
August 10, 2005 7:08:19 AM

Archived from groups: rec.photo.digital (More info?)

Proteus wrote:
>
> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

I have a point and shoot which does ISO 85 but I have no control over
it
--
Paul (And I'm, like, "yeah, whatever!")
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
Anonymous
August 10, 2005 7:08:20 AM

Archived from groups: rec.photo.digital (More info?)

On Wed, 10 Aug 2005 03:08:19 GMT, Paul Heslop wrote:

> I have a point and shoot which does ISO 85 but I have
> no control over it

Unlike my P&S which will only use ISO 100 or 200 in (fully) AUTO
mode. In all other modes, ISO 64 can be selected.
Anonymous
August 10, 2005 8:14:16 AM

Archived from groups: rec.photo.digital (More info?)

On 10 Aug 2005 00:40:02 -0700, Craig Dunn wrote:

> I've got a Canon A95 P&S which has a min ISO of 50 - but my 20D, like
> the 10D, has a floor of 100. I've not really noticed any particular
> hinderance to having a minimum of 100 on my DSLR, but then, different
> photographers will want different things I guess.

You've probably got exactly what you need with those cameras.
With its superior sensor, the 20D probably wouldn't produce better
images with an ISO lower than 100, so it doesn't have one. The A95
on the other hand probably gives you marginally better shots at ISO
50 than at ISO 100. Have you ever made comparison shots at 50 and
100? If there are any noticeable differences at high magnification,
I imagine they're much less than what you'd see with shots taken at
ISO 200 and 400.
Anonymous
August 10, 2005 8:24:11 AM

Archived from groups: rec.photo.digital (More info?)

Proteus <nospam@nowhere.net> writes:
> My Canon 10D iso only goes down to iso 100. I am curious if other
> digital SLRs can go below that, since film cameras can use eg iso 25
> film (like Kodachrome 25). And if not, why can't digital go below
> iso 100?

Any digital sensor has a floor ISO sensitivity which is the readout of
the charge collected in its photon wells without any amplification.
Higher ISO settings is achieved by amplyfying the analogue readout of
photon wells. This makes the sensor appear more sensitive, but also
amplifies any noise present in the signal.

Setting ISO below this floor serves no purpose. The photon wells
will simply overflow, resulting in a reduced dynamic range.

Most sensors seems to have ISO 100 as their floor, but some are
even higher (e.g. the Nikon D70s, which starts at ISO 200).

I guess it would be possible to design a sensor with ISO 25 as
its baseline sensitivity - but as this probably would make it
very noisy at higher ISO levels, such a sensor would have a
very limited appeal.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
------------------------------------------------------------------------
Kodak DCS460, Canon Powershot G5, Olympus 2020Z
------------------------------------------------------------------------
Anonymous
August 10, 2005 10:10:59 AM

Archived from groups: rec.photo.digital (More info?)

ASAAR wrote:
>
> On Wed, 10 Aug 2005 03:08:19 GMT, Paul Heslop wrote:
>
> > I have a point and shoot which does ISO 85 but I have
> > no control over it
>
> Unlike my P&S which will only use ISO 100 or 200 in (fully) AUTO
> mode. In all other modes, ISO 64 can be selected.

My replacement cam, the c-725 Oly, has only 100, 200 or 400. It could
really have done with that 85.
--
Paul (And I'm, like, "yeah, whatever!")
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
Anonymous
August 10, 2005 11:48:30 AM

Archived from groups: rec.photo.digital (More info?)

Craig Dunn wrote:
>
> I've got a Canon A95 P&S which has a min ISO of 50 - but my 20D, like
> the 10D, has a floor of 100. I've not really noticed any particular
> hinderance to having a minimum of 100 on my DSLR, but then, different
> photographers will want different things I guess.

what I have noticed, since getting my newer cam, is that some of the
better pics I took on my point and shoot were the ones which used the
85. This Oly, if left fully auto, seems to enjoy using ISO 200 which
is pretty crud , specially on people shots.
--
Paul (And I'm, like, "yeah, whatever!")
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
Anonymous
August 10, 2005 11:53:16 AM

Archived from groups: rec.photo.digital (More info?)

In article <A%cKe.14064$Tt6.4424@fe04.lga>, Proteus says...
> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

ISO 50 on an Olympus 8080
--

Alfred Molon
------------------------------
Olympus 4040, 5050, 5060, 7070, 8080, E300 forum at
http://groups.yahoo.com/group/MyOlympus/
Olympus E300 resource - http://myolympus.org/E300/
Anonymous
August 10, 2005 1:21:53 PM

Archived from groups: rec.photo.digital (More info?)

Proteus wrote:
> My Canon 10D iso only goes down to iso 100. I am curious if other
> digital SLRs can go below that, since film cameras can use eg iso 25
> film (like Kodachrome 25). And if not, why can't digital go below iso
> 100?

The limit is that there is a finite number of photo-electrons which can be
accommodated at each pixel. So if you designed a sensor with a bigger
well, or one where the conversion efficiency between photons and
photo-electrons was worse (i.e. a less sensitive sensor), then you could
get a lower ISO sensor. The trade-offs seem to be that, for a DSLR-sized
sensor, ISO 100 is today's lower limit and provides adequately low noise
performance.

The smaller pixel size and smaller well size if the main difference
between DSLRs and ZLR/point-and-shoot cameras, resulting in considerably
lower noise at higher ISOs (e.g. 800) in DLSRs.

David
Anonymous
August 10, 2005 1:23:32 PM

Archived from groups: rec.photo.digital (More info?)

On Wed, 10 Aug 2005 02:29:58 GMT, "[BnH]" <b18@nsw.gov.au> wrote:

>8 on Kodak DSLR line.

???
http://www.dpreview.com/reviews/kodakslrc/page2.asp
>
>=bob=
>
>"Proteus" <nospam@nowhere.net> wrote in message
>news:A%cKe.14064$Tt6.4424@fe04.lga...
>> My Canon 10D iso only goes down to iso 100. I am curious if other digital
>> SLRs can go below that, since film cameras can use eg iso 25 film (like
>> Kodachrome 25). And if not, why can't digital go below iso 100?
>>
>

--
Bill Funk
replace "g" with "a"
funktionality.blogspot.com
Anonymous
August 10, 2005 1:37:16 PM

Archived from groups: rec.photo.digital (More info?)

Proteus wrote:
> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?
>

In a film, going to lower speed emulsion gives you higher resolution
(smaller grain size). Once you build a CCD chip, with a given
resolution, there is no advantage in changing speed to lower than the
native speed of the silicon.
Anonymous
August 10, 2005 1:41:01 PM

Archived from groups: rec.photo.digital (More info?)

Don Stauffer wrote:
> Proteus wrote:
>
>> My Canon 10D iso only goes down to iso 100. I am curious if other digital
>> SLRs can go below that, since film cameras can use eg iso 25 film (like
>> Kodachrome 25). And if not, why can't digital go below iso 100?
>>
>
> In a film, going to lower speed emulsion gives you higher resolution
> (smaller grain size).

Very much subject to laws of diminishing returns, or perhaps similar to
reciprocity failure.

Once you build a CCD chip, with a given
> resolution, there is no advantage in changing speed to lower than the
> native speed of the silicon.

Sounds right, but I don't know enough about silicon.

--
John McWilliams

Max thought the night-time burglary at the California surfing museum
would be a safe caper, but that was before he spotted the security cop
riding a bull mastiff, blond hair blowing in the wind, and noticed the
blue-and-white sign wired to the cyclone fence, "Guard dude on doggy."
August 10, 2005 2:10:48 PM

Archived from groups: rec.photo.digital (More info?)

On Tue, 09 Aug 2005 20:45:26 -0500, Proteus <nospam@nowhere.net> wrote:

> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

Canon S2 IS does ISO 50
Anonymous
August 10, 2005 3:16:16 PM

Archived from groups: rec.photo.digital (More info?)

"Proteus" <nospam@nowhere.net> wrote in message
news:A%cKe.14064$Tt6.4424@fe04.lga...
| My Canon 10D iso only goes down to iso 100. I am curious if other digital
| SLRs can go below that, since film cameras can use eg iso 25 film (like
| Kodachrome 25). And if not, why can't digital go below iso 100?


My Fuji Finepix S5500 goes down to 64; my friend's Canon G5 goes to 50.
Anonymous
August 10, 2005 4:05:05 PM

Archived from groups: rec.photo.digital (More info?)

Since a neutral density filter can be used to effectively lower the
ISO, why would digital cameras even need to have lower ISO's built-in?

Mark
Anonymous
August 10, 2005 4:55:43 PM

Archived from groups: rec.photo.digital (More info?)

Proteus <nospam@nowhere.net> writes:

> My Canon 10D iso only goes down to iso 100. I am curious if other digital
> SLRs can go below that, since film cameras can use eg iso 25 film (like
> Kodachrome 25). And if not, why can't digital go below iso 100?

To my way of thinking, a camera that offers less than ISO 100, means that the
sensor is noisy, and that the engineers judged it could not deliver the quality
they wanted at ISO 100.

--
Michael Meissner
email: mrmnews@the-meissners.org
http://www.the-meissners.org
Anonymous
August 10, 2005 4:57:32 PM

Archived from groups: rec.photo.digital (More info?)

Paul Heslop <paul.heslop@blueyonder.co.uk> writes:

> Craig Dunn wrote:
> >
> > I've got a Canon A95 P&S which has a min ISO of 50 - but my 20D, like
> > the 10D, has a floor of 100. I've not really noticed any particular
> > hinderance to having a minimum of 100 on my DSLR, but then, different
> > photographers will want different things I guess.
>
> what I have noticed, since getting my newer cam, is that some of the
> better pics I took on my point and shoot were the ones which used the
> 85. This Oly, if left fully auto, seems to enjoy using ISO 200 which
> is pretty crud , specially on people shots.

Generally you get the best shots on any camera by using the lowest ISO.
However, you often times need to bump the ISO if there is not enough light to
take pictures at your target aperture and shutter speeds.

--
Michael Meissner
email: mrmnews@the-meissners.org
http://www.the-meissners.org
Anonymous
August 10, 2005 6:20:44 PM

Archived from groups: rec.photo.digital (More info?)

In article <vinif1l67pbmtolvpil41u86fkdu24tk14@4ax.com>,
ASAAR <caught@22.com> wrote:

> On Tue, 09 Aug 2005 20:45:26 -0500, Proteus wrote:
>
> > My Canon 10D iso only goes down to iso 100. I am curious if other digital
> > SLRs can go below that, since film cameras can use eg iso 25 film (like
> > Kodachrome 25). And if not, why can't digital go below iso 100?
>
> I don't know how accurate this information is, coming from
> mini-reviews in a UK camera magazine, and that ISO 6 seems like it
> would be a typo, where it may have been intended to be ISO 60.
>
> 1. Kodak DCS PRO SLR/n: ISO 80 to 600
>
> 2. Kodak DCS PRO SLR/c: ISO 6 to 800 (fully calibrated) and ISO 1000
> to 1600 (extended mode).
>
> As for why digital SLRs don't go below 100, consider where lower
> ISOs would be used. In very bright light.

With film the lower ISO's are used for more sharpness, not just bright
light. The silver grains are smaller. Anyway, it is silly to compare
ISO's between film and digital.

> The sensor already be on
> the verge of blowing highlights if the exposure isn't restricted.
> If the ISO was reduced the camera would compensate by changing the
> exposure (longer shutter speed and/or wider aperture) while
> lessening the sensor's amplification. But that would result in a
> sensor already near overflowing with photons (each sensor pixel site
> has a limit to the number of photons it can accept) trying to
> capture perhaps 2 or 4 times more photons. This would probably
> result in much greater areas of blown highlights. There is a much
> better method to simulate a lower ISO - use an ND filter. :) 
>
> Note: I just saw Gisle's reply which said:
>
> > I guess it would be possible to design a sensor with ISO 25 as
> > its baseline sensitivity - but as this probably would make it
> > very noisy at higher ISO levels, such a sensor would have a
> > very limited appeal.
>
> That's a good evaluation of Kodak's DCS PRO SLRs :) 

--

http://home.nc.rr.com/christianbonanno/
Anonymous
August 10, 2005 6:20:45 PM

Archived from groups: rec.photo.digital (More info?)

On Wed, 10 Aug 2005 14:20:44 GMT, CFB wrote:

> With film the lower ISO's are used for more sharpness, not just bright
> light. The silver grains are smaller. Anyway, it is silly to compare
> ISO's between film and digital.

Exactly. But because lowering the ISO with digital sensors does
not improve sharpness, we're left to see how lowering it would
effect a change, and brightness/sensor well depth does have a part
to play.
Anonymous
August 10, 2005 6:34:21 PM

Archived from groups: rec.photo.digital (More info?)

In article <1123644531.944551.6770@g43g2000cwa.googlegroups.com>,
"Bill Hilton" <bhilton665@aol.com> wrote:

> >Proteus writes ...
> >
> >And if not, why can't digital go below iso 100?
>
> Gisle's post explains this well, I think.
>
> >My Canon 10D iso only goes down to iso 100. I am curious if other
> >digital SLRs can go below that
>
> My 1D MII has an expansion mode that lets you shoot at 50 for exposure
> purposes even though it's not really better than 100. We use it often
> when we need an extra stop, typically for blurring things. Here are a
> few semi-abstract images my wife took last week at f/32, iso 50 and
> with a pol filter (which slows it down another 1-2 stops) to slow the
> shutter speed as we were driving home from a trip in mid-day light as
> examples of when you might find a lower ASA handy ...
> http://members.aol.com/bhilton665/blurs/vla_88.jpg
> http://members.aol.com/bhilton665/blurs/bridge_354.jpg
> http://members.aol.com/bhilton665/blurs/dunno_926.jpg
> http://members.aol.com/bhilton665/blurs/trees_342.jpg
> http://members.aol.com/bhilton665/blurs/burn_245.jpg
>
> Bill
Did you manipulated those images in photoshop? If you zoom in on "Burn"
you will see the pixels are stretched vertically.

--

http://home.nc.rr.com/christianbonanno/
Anonymous
August 10, 2005 7:28:15 PM

Archived from groups: rec.photo.digital (More info?)

On Tue, 09 Aug 2005 20:45:26 -0500, Proteus <nospam@nowhere.net>
wrote:

>My Canon 10D iso only goes down to iso 100. I am curious if other digital
>SLRs can go below that, since film cameras can use eg iso 25 film (like
>Kodachrome 25). And if not, why can't digital go below iso 100?

I have an old HP C912 camera which will do ISO=25 but it is a
unique digital camera in several ways, some good & some not but it
still gets used for some things even though it only has a 2.24MP (2/3"
CCD).

http://www.steves-digicams.com/c912.html#specs

For a P&S digital camera that's a "huge" sensor for "only 2.24MP"
resolution but it's needed because light must travel through a
semi-transmissive mirror to get to the CCD. This is done so that a
TTL image can be had in the "optical" viewfinder without need to move
the mirror out of the optical path as is needed with both D-SLR & SLR
cameras.

In many ways it was branch on the evolutionary path of
consumer digital cameras but it clearly has limited appeal & as far as
I know, nobody else has produced a consumer camera like this 1! In
any case ZLR seem to have become the other branch that grow as this 1
died off. Now I have a few Canon P&S's & a D-SLR as well as an
Olympus C-7070WZ (primarily for it's 27.2mm-110mm wide angle lens & a
ton of user programmable features). However the HP C912 still see's
occasional use & how knows, some day it may be selling as a
collector's item on ebay for much more than I paid for it. lol Well,
I can dream, can't' I?

Respectfully, DHB


..



"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918
Anonymous
August 10, 2005 8:01:34 PM

Archived from groups: rec.photo.digital (More info?)

Bill,
The first shot "vla_88" didn't too much for me, probably because I
didn't understand it. Just what were those white ghost looking things
anyway? The rest though I really liked, sort of a photographic art
form. Please give your wife my compliments.
Paul


Bill Hilton wrote:
>>Proteus writes ...
>>
>>And if not, why can't digital go below iso 100?
>
>
> Gisle's post explains this well, I think.
>
>
>>My Canon 10D iso only goes down to iso 100. I am curious if other
>>digital SLRs can go below that
>
>
> My 1D MII has an expansion mode that lets you shoot at 50 for exposure
> purposes even though it's not really better than 100. We use it often
> when we need an extra stop, typically for blurring things. Here are a
> few semi-abstract images my wife took last week at f/32, iso 50 and
> with a pol filter (which slows it down another 1-2 stops) to slow the
> shutter speed as we were driving home from a trip in mid-day light as
> examples of when you might find a lower ASA handy ...
> http://members.aol.com/bhilton665/blurs/vla_88.jpg
> http://members.aol.com/bhilton665/blurs/bridge_354.jpg
> http://members.aol.com/bhilton665/blurs/dunno_926.jpg
> http://members.aol.com/bhilton665/blurs/trees_342.jpg
> http://members.aol.com/bhilton665/blurs/burn_245.jpg
>
> Bill
>
Anonymous
August 10, 2005 11:39:52 PM

Archived from groups: rec.photo.digital (More info?)

Michael Meissner wrote:
>
> Paul Heslop <paul.heslop@blueyonder.co.uk> writes:
>
> > Craig Dunn wrote:
> > >
> > > I've got a Canon A95 P&S which has a min ISO of 50 - but my 20D, like
> > > the 10D, has a floor of 100. I've not really noticed any particular
> > > hinderance to having a minimum of 100 on my DSLR, but then, different
> > > photographers will want different things I guess.
> >
> > what I have noticed, since getting my newer cam, is that some of the
> > better pics I took on my point and shoot were the ones which used the
> > 85. This Oly, if left fully auto, seems to enjoy using ISO 200 which
> > is pretty crud , specially on people shots.
>
> Generally you get the best shots on any camera by using the lowest ISO.
> However, you often times need to bump the ISO if there is not enough light to
> take pictures at your target aperture and shutter speeds.
>
> --
> Michael Meissner
> email: mrmnews@the-meissners.org
> http://www.the-meissners.org

It's a really dirty 200 and 400 ISO, this cam. I did some pics outside
of the grandkids playing and they looked like they had huge freckles.
:o (
--
Paul (And I'm, like, "yeah, whatever!")
-------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/
Anonymous
August 11, 2005 2:23:37 AM

Archived from groups: rec.photo.digital (More info?)

In article <m3zmrpwx2o.fsf@glinda.the-meissners.org>, Michael Meissner
says...

> To my way of thinking, a camera that offers less than ISO 100, means that the
> sensor is noisy, and that the engineers judged it could not deliver the quality
> they wanted at ISO 100.

I'd rather say that the sensor is not too sensitive.

The lowest ISO is the true ISO of a sensor - with all other ISOs the
wells of the pixels only fill partially.
--

Alfred Molon
------------------------------
Olympus 4040, 5050, 5060, 7070, 8080, E300 forum at
http://groups.yahoo.com/group/MyOlympus/
Olympus E300 resource - http://myolympus.org/E300/
Anonymous
August 11, 2005 2:24:38 AM

Archived from groups: rec.photo.digital (More info?)

In article <1123700705.914354.278090@g49g2000cwa.googlegroups.com>,
redbelly says...
> Since a neutral density filter can be used to effectively lower the
> ISO, why would digital cameras even need to have lower ISO's built-in?

So that you don't have to carry the ND filter with you.
--

Alfred Molon
------------------------------
Olympus 4040, 5050, 5060, 7070, 8080, E300 forum at
http://groups.yahoo.com/group/MyOlympus/
Olympus E300 resource - http://myolympus.org/E300/
Anonymous
August 11, 2005 5:03:41 AM

Archived from groups: rec.photo.digital (More info?)

"redbelly" <redbelly98@yahoo.com> wrote in message
news:1123700705.914354.278090@g49g2000cwa.googlegroups.com...
> Since a neutral density filter can be used to effectively lower
> the ISO, why would digital cameras even need to have lower
> ISO's built-in?

Lower noise. Even the omni-present photon shot noise will be reduced.
Unfortunately dynamic range is probably compromised at the same time,
so it is a bit of a trade-off depending on the subject.

Bart
Anonymous
August 11, 2005 1:09:37 PM

Archived from groups: rec.photo.digital (More info?)

DHB wrote:
> On Tue, 09 Aug 2005 20:45:26 -0500, Proteus <nospam@nowhere.net>
> wrote:
> I have an old HP C912 camera which will do ISO=25 but it is a
> unique digital camera in several ways, some good & some not but it
> still gets used for some things even though it only has a 2.24MP (2/3"
> CCD).
>
> http://www.steves-digicams.com/c912.html#specs
>
> For a P&S digital camera that's a "huge" sensor for "only 2.24MP"
> resolution but it's needed because light must travel through a
> semi-transmissive mirror to get to the CCD. This is done so that a
> TTL image can be had in the "optical" viewfinder without need to move
> the mirror out of the optical path as is needed with both D-SLR & SLR
> cameras.

And that probably explains the ISO25: Two stops of loss through the
mirror to an ISO 100 sensor.

-Mike
!