Difficult technical question on ISO & light

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huerew wrote:

> Let's see if I catch some guru's attention with this subject :-)
>
> I have recently bought a Canon S50 but probably any other camera would
> not change the question. It would probably be the same even with a film
> camera + lab processing.
>
> I can't understand how the following thing works:
>
> Case a.
> I take a photo by night at ISO 50 without flash. In the photo I can see
> the streetlights which have white color (RGB = 255,255,255), but all the
> rest is very dark.

All that is is that the light 'burned' through and was probably much higher that
what you measured in photoshop... 255 is at the limit of each color, so you got
clipped highlights. The rest of the frame was simply udnerexposed (0, or maybe
a bit more on 255).

>
> Case b.
> I take the same photo (same time and lens aperture) at ISO 400 without
> flash. This time I can see everything. The streetligts are always white
> at RGB = 255,255,255 .

Again, the streetlights are burned out and you're at the limit (in fact even
further, but it doesn't matter). But now, 3 stops more sensitivity so other
areas begin to fill in.

>
> I cannot understand how the algorithm works, and not even the physics
> behind all this: how can the ratio between the luminosity of the
> streetlight and the luminosity of the walls of the houses CHANGE
> depending on the ISO (50 vs 400)??

In an 8 bit per color case, a pixel can have a value of 0 (black) to 255 (full
saturation). When all three color elements are 0, (black); when all three color
elements are 255 it is pure white. When all 3 color elements are equal, but in
between, you get a shade of grey. When all 3 are 128, you get middle grey (18%
grey).

In you case however you had a scene with such low light that nothing registered
at ISO 50 except those parts of the scene that were very strong (too strong).
Near the lights you may have a halo area that quickly rolls from 255 down to
near 0 quickly.

At 400, you got more detail in the dark areas ... but the light was even further
beyond the sensitivity of the sensor and fully saturated.

>
> One could say that the reason for this is the clipping, that is, at 400
> ISO the streetlights were more luminous than RGB = 255,255,255 but they
> have been clipped to that value.

Yep.

>
> But I think this is NOT the reason because if it should be, then what
> would be the explanation for the fact that EVERY picture I take in a
> whatever dark environment ALWAYS contains at least 1 pixel at with one
> of the three components (R,G or B) at 255? It seems like there is an
> algorithm which multiplies the information from the CCD until at least 1
> pixel of the image reaches the maximum value (255).

A scene may easilly have more range than your film or CCD/CMOS can handle. Thie
means that either one end will be over exposed and other perhaps okay; or vice
versa ... and if the scene is really wide you will have both unexcited pixels
(too dark) and saturated (clipped) pixels. This is why one strategy is to place
the highlights at the extreme right of the histogram, and let the rest fall
where it may.

There is no compressing or decompressing. The sensor can hanlde so much scene
latitude and you the photographer has to place it correctly... in auto mode,
presumably the camera does this well... presumably.

Shoot RAW, put your hightlights at the extreme right of the histogram and you
will get the most detail that the camera can record in that scene.

Cheers,
Alan


--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

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pk wrote:
>
> Whats wrong with you? You are making this too complicated. And did you
> really need to cross post this to half a dozen newsgroups?

I do agree this is should not have been crossposted.

> Digital film (senor) sensitivity are equivalent to film.

Incorrect. CCD or CMOS sensors are not equal to film; one is
not equivalent to then other. There are differenent physics
and imaging properties that apply to any giving situation.

Film has the ability to _accumulate_ light and endure long
exposures or multiple exposures that can capture detail
in the dimmest of situations. Reciprocity failure is the
only factor. Silicon simply can't do this and is limited by
both exposure latitude and length of exposure.

> The higher
> the ISO the more sensitive the film is to light. So the higher the ISO
> on a digital camera the more sentive to light the digital sensor is.

Digital sensors have a _nominal_ "speed" at which they
produce the best quality image. When you alter that speed
the image quality goes down. Film can be rated at a different
speeds and still produce quality results because as development
of film is altered, effective speed also alters. Also, a "slow"
film can be simply be exposed for a longer time than a faster
film, and achieve the same results. No loss in image quality.

Film can be exposed for hours. Try that with a digital sensor.
It simply one of the differences between these two imaging
mediums.


> If one setting is higher than the other its going to be more sensative
> to light and therfore capture more light in the scene.
>
> Back to your question about the street lights. Obviously it will catch
> whatever has the most light in a given scene, so the streetlights will
> be brighter, even washed out without detail, because they are the
> brightest part of the scene, while the rest of the scene is only
> somewhat visable by comparision. Think about shooting the sun. Try
> shooting a sunset. You will get an opposite effect in a bright scene.
> The sun will be totally bright while while the rest of the landscape
> will be pitch black because the sensor cannot hold to extremes of
> light.
>
> If you are in a dark scene use a tripod with lower ISO settings. If
> you shoot handheld you will either get blur or a lot of grain, with
> either digial or film. Also try to avoid extremes in lighting
> especailly in dark scenes as you will get white washout from bright
> sources of light like streetlights.
>
> huerew <huerew@hhh.com> wrote in message news:<clrqmc01h3p@news3.newsguy.com>...
> > Let's see if I catch some guru's attention with this subject :-)
> >
> > I have recently bought a Canon S50 but probably any other camera would
> > not change the question. It would probably be the same even with a film
> > camera + lab processing.
> >
> > I can't understand how the following thing works:
> >
> > Case a.
> > I take a photo by night at ISO 50 without flash. In the photo I can see
> > the streetlights which have white color (RGB = 255,255,255), but all the
> > rest is very dark.
> >
> > Case b.
> > I take the same photo (same time and lens aperture) at ISO 400 without
> > flash. This time I can see everything. The streetligts are always white
> > at RGB = 255,255,255 .
> >
> > I cannot understand how the algorithm works, and not even the physics
> > behind all this: how can the ratio between the luminosity of the
> > streetlight and the luminosity of the walls of the houses CHANGE
> > depending on the ISO (50 vs 400)??
> >
> >
> >
> > One could say that the reason for this is the clipping, that is, at 400
> > ISO the streetlights were more luminous than RGB = 255,255,255 but they
> > have been clipped to that value.
> >
> > But I think this is NOT the reason because if it should be, then what
> > would be the explanation for the fact that EVERY picture I take in a
> > whatever dark environment ALWAYS contains at least 1 pixel at with one
> > of the three components (R,G or B) at 255? It seems like there is an
> > algorithm which multiplies the information from the CCD until at least 1
> > pixel of the image reaches the maximum value (255).
> >
> > BUT THEN, if such a normalizing algorithm exists, again the photos in
> > case a. and b. should present the same luminosity ratio between the
> > streetlights and the walls of the houses, while it is not like this.
> >
> > So what?
> >
> > Thanks in advance.

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Chris Brown wrote:
>
> In article <4181C14A.D6ECD4FA@aol.com>,
> Tom Phillips <nospam777@aol.com> wrote:
> >
> >Film can be exposed for hours. Try that with a digital sensor.
> >It simply one of the differences between these two imaging
> >mediums.
>
> You really should avoid such pontifications unless you're absolutely certain
> you're correct, as you aren't in this case. Canon's current DSLRs, to take
> one example, manage perfectly hapilly with multi-hour exposures. The only
> major problem is that holding the shutter open that long may drain the
> battery.


uh huh... multi-hour digital. And no noise due to heat. right.
(and heat is *inherent* in digital sensor exposure...)

Show me a "multi hour" digital exposure.

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Tom Phillips wrote:
>
> Chris Brown wrote:
> >
> > In article <4181C14A.D6ECD4FA@aol.com>,
> > Tom Phillips <nospam777@aol.com> wrote:
> > >
> > >Film can be exposed for hours. Try that with a digital sensor.
> > >It simply one of the differences between these two imaging
> > >mediums.
> >
> > You really should avoid such pontifications unless you're absolutely certain
> > you're correct, as you aren't in this case. Canon's current DSLRs, to take
> > one example, manage perfectly hapilly with multi-hour exposures. The only
> > major problem is that holding the shutter open that long may drain the
> > battery.
>
> uh huh... multi-hour digital. And no noise due to heat. right.
> (and heat is *inherent* in digital sensor exposure...)
>
> Show me a "multi hour" digital exposure.

And I don't mean astrophotography.

The ability of the canon EOS to do astrophotography is
in part due to the employment of a larger pixel. Larger
pixels mean a better signal and less noise, *but* (also
less pixel resolution. So _pictorial_ resolution is
sacrificed for better signal and less noise. This is hardly
comparable with film, where resolution abilities is not
based on large grain size, but _small_ grain size and where
exposure and signal frequency is on a molecular level, not
a pixel level.

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In article <4181DC73.F1671D33@aol.com>,
Tom Phillips <nospam777@aol.com> wrote:

>Talking lighting and exposure here. And again you ignore
>nyquist. Also, on average a 400 speed 35mm film has the
>equivalent of 24 million pixels.

Oh wow, a real 35mm pixel-counter. I thought the last one of those in the
wild had died out years ago...

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"Justín Käse" wrote:
>
> In Message-ID:<41820CEB.85C0F622@aol.com> posted on Fri, 29 Oct 2004
> 03:27:15 -0600, Tom Phillips wrote:
>
> >
> >
> >"Justín Käse" wrote:
> >>
> >> In Message-ID:<4181C14A.D6ECD4FA@aol.com> posted on Thu, 28 Oct 2004
> >> 22:04:29 -0600, Tom Phillips wrote:
> >>
> >> >Film can be exposed for hours. Try that with a digital sensor.
> >> >It simply one of the differences between these two imaging
> >> >mediums.
> >>
> >> I used to have a rule of thumb with ASA100 film at f5.6, a scene lit by
> >> full moonlight took five minutes. This would bring out (saturate) all
> >> the colors, and providing there was no wind, give good resolution to
> >> leaves and foliage.
> >> I haven't tried it with the digicam yet, but thinking about what's been
> >> discussed, there wouldn't be any reciprocity failure to worry about as
> >> there would be no accumulative chemistry happening,
> >
> >reciprocity failure isn't due to chemistry, but related
> >to quantum physics...
>
> ...which is the basis of chemistry, no?

I suppose one could say it's photochemical. Technically
it's related to the intermittency effect, or the amount
of light available. Reciprocity failure at longer exposures
results from low irradiance of silver halides, meaning there
is too long a time -- too long a gap -- between the halide
molecules being struck with enough photons to initiate
nucleation and the formation of latent silver (photolysis;
typically three photons are required.) This is also why in
photography a 2+2 exposure does not equal a single exposure
of the same continuous length. But since silver halides can
accumulate exposure, _adding_ additional exposure (i.e.
a reciprocity correction) will compensate -- i.e., multiple
exposures are applicable.

Silicon sensors do not this, as they do not accumulate
multiple exposures and over exposure inherently begets
additional noise.

> Quantum theory is just the mind's imagination trying to comprehend
> phenomena that exceed our technical abilities of resolution.

You've lost me. Sorry.

> Counting subatomic particles smaller than the atomic probes we are
> currently limited to using, is like trying to read braille with your
> elbow.
> talk about nyquist limits. <g>

Well, nucleation occurs on a molecular level in silver
halide imaging. Silcon imaging requires a much greater
incidence of photons (photoelectrons) to generate a
signal for the same tonal "exposure."

> >>neither would there
> >> be any increased darkness penetration effect either. Guess I won't be
> >> throwing away all my film cameras just yet. <g>
> >
> >No you shouldn't :-) In order for digital images to gather
> >more light, larger pixels are required.
>
> I thought pixel sensitivity was a function of semiconductor gain and was
> dependent on the difference between the idle state and the excited
> state, thus the astronomical use of refrigerants to chill CCDs as much
> as possible to enhance that difference.

Larger pixels help increase the gain also.

> I think it's only modern digicam sensors that use selective bias
> voltages to simulate ISO ratings for user convenience in varying
> situations, whereas astro-photographers strive for the utmost gain, and
> aren't concerned with desensitizing their equipment for "beach" pics.

I _think_ we agree.

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"pk" <pkim0908@gmail.com> wrote in message
news:af6200a1.0410281933.7416b5ea@posting.google.com...
> Whats wrong with you? You are making this too complicated. And did you
> really need to cross post this to half a dozen newsgroups?
> [...]
> huerew <huerew@hhh.com> wrote in message
> news:<clrqmc01h3p@news3.newsguy.com>...
>> Let's see if I catch some guru's attention with this subject :-)

Overanalysis Paralasis.

It seems that below the confusion regarding exposure is a misunderstanding
regarding the eye and film. The eye (and brain) process an image so that you
see a great range of brightness. Film is not that way. Look to the film
sensitivity chart where film's sensitivity to gradations of light is plotted
in a log curve. Better now? So simple when you get that.

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"imbsysop" <imbsysop@yahoo.com> wrote in message
newshj4o0170118qehg72lt3e1fj6hf438g0m@4ax.com...
> >> >> >Talking lighting and exposure here. And again you ignore
> >> >> >nyquist. Also, on average a 400 speed 35mm film has the
> >> >> >equivalent of 24 million pixels.
> >> >>
> >> >> Oh wow, a real 35mm pixel-counter. I thought the last one of those
in the
> >> >> wild had died out years ago...

Kodak quotes 24 MP as the equivalent of 35mm film, on their website.
Whether you can observe the difference in image quality is another issue.

I would accept Kodak's assessment, because I consider them qualified to make
it.

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In article <41823255.BC08FE81@aol.com>,
Tom Phillips <nospam777@aol.com> wrote:
>
>>
>> The medium format does give me superior image quality to both of them, and
>> it's dramatically superior. The relative difference between the digital and
>> 35mm, in comparison, is not worth bothering with. They're both adequate for
>> an A4 print, and ropey for an A3 print.
>
>Never shot Kodachrome 25 or 64, I gather...

Usually Velvia 50, although I'm doing a lot more Provia 100F these days.

>The questionn is, why is this even a debate?

It's not - in the eyes of nearly everyone who regarded this as some kind of
"contest", 35mm "lost" years ago, with the previous genertion of DSLRs.
You're trotting out the sort of stuff that used to infest r.p.e.35mm and
r.p.d about 2-4 years ago. Pretty much everyone else has accepted reality
and moved on.

>For _pictorial_ imaging, film is the better medium. The
>facts bear this out.

I quite agree, you just need the film to be 6cm wide or more to compete
in the quality stakes these days.

>Digital,imaging is not photographic. It does not produce
>a photograph.

If you say so.

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In article <lhsgd.13512$ta5.12299@newsread3.news.atl.earthlink.net>,
Jeremy <jeremy@nospam.thanks.com> wrote:
>
>Kodak quotes 24 MP as the equivalent of 35mm film, on their website.

Large film manufacturer gives optimistic interpretation of raw data
regarding own product shock! Film at eleven (no pun intended).

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Chris Brown wrote:
>
> In article <26k952-5k8.ln1@narcissus.dyndns.org>,
> Chris Brown <cpbrown@ntlworld.no_uce_please.com> wrote:
> >In article <4182032A.D3B720F7@aol.com>,
> >Tom Phillips <nospam777@aol.com> wrote:
> >
> >>uh huh... multi-hour digital. And no noise due to heat. right.
> >>(and heat is *inherent* in digital sensor exposure...)
> >>
> >>Show me a "multi hour" digital exposure.
> >
> >OK, I'll take one tonight and upload it. Have to be of something indoors and
> >boring, I'm afraid, as there's too much light pollution where I live to do
> >such a long exposure outside, and the weather's pretty nasty atm as well.
>
> In the meantime, here's a 30 minute one to be going on with. I downsized it
> for the web, but included a 1:1 crop in part of the pic, so that you can see
> just how "terrible" the noise is.
>
> Ambient temperature was about 15C.
>
> http://homepage.ntlworld.com/narcissus/30mins.jpg

30 minutes is not "multi hour."

CMOS sensors are an improvement over CCD sensors.
But,caveats still exist. For exmaple, it is still
a fact of electronics that the bigger the pixel the
better the signal and the less noise. Canon, in fact
states on their web site that "When photographing dark o
bjects like stars, conditions at the place of use, such
as the temperature and the length of exposure, may have
a noticeable effect on the noise level of the camera...."

Canon also recommends the EOS 10D for such imaging, on
the basis that the pixels are larger and thus produce
a better signal and less ingherent noise.

Hours and hours is what you claimed. Noise is still going
to be an issue. The issue with film is reciprocity failure,
but this is easily compensated for and there is no noise.
The fact is, due to Nyquist digital sensors suitable for
longer exposures simply are not going to match the detail
and resolution possible with film.

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imbsysop wrote:
>
> On Fri, 29 Oct 2004 06:06:53 -0600, Tom Phillips <nospam777@aol.com>
> wrote:
>
> >
> >
> >Chris Brown wrote:
> >>
> >> In article <418210F6.561BFC92@aol.com>,
> >> Tom Phillips <nospam777@aol.com> wrote:
> >> >
> >> >
> >> >Chris Brown wrote:
> >> >>
> >> >> In article <4181DC73.F1671D33@aol.com>,
> >> >> Tom Phillips <nospam777@aol.com> wrote:
> >> >>
> >> >> >Talking lighting and exposure here. And again you ignore
> >> >> >nyquist. Also, on average a 400 speed 35mm film has the
> >> >> >equivalent of 24 million pixels.
> >> >>
> >> >> Oh wow, a real 35mm pixel-counter. I thought the last one of those in the
> >> >> wild had died out years ago...
> >> >
> >> >
> >> >No, stupid.
> >>
> >> I bet that's what you say to all the girls.
> >>
> >> >It's something that's been scientifically determined
> >> >by eminent photo scientists based on the number of absorbed photons.
> >>
> >> Your alluded to "scientific determination" doesn't match the reality
> >> observed by those of us who shoot multiple systems. In said observed
> >> reality, 35mm film can just about edge out 6 megapixel DSLRs at low ISO,
> >
> >***ONLY*** at typical machine print sizes. In fact, any 35mm
> >image can be *enlarged* to as much as 10 times it's resolution,
> >revealing additional image detail. No digital image of a similar
> >pixel resolution can achieve this capability. A higher resolution
> >capture is required.
> >
> >This is simply due to the fact that silver halides record
> >tonal/image information on a molecular level as opposed to
> >a much larger pixel. This is an inherent distinction between
> >these two imaging mediums.
>
> off track .. this only happens if the emulsion would consist of free
> molecules in a monomolecular layer at 100% molecular density .. it is
> not, even if microcrystaline it still is crystaline .. and hence you
> do not get a 100 chemical reaction to light ..

Silver hailde exposure occurs at the molecular level.

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Ken Alverson wrote:
>
> "Tom Phillips" <nospam777@aol.com> wrote in message
> news:41823255.BC08FE81@aol.com...
> >
> > Photography produces a photograph. And a photograph is an
> > image written on photosensitive materials by the direct
> > action of light. Digital imaging is electronic and about
> > as "photographic" as your television cameraman broadcasting
> > to your T.V. set. Again, no photograph.
>
> Photograph, from the greek "photo-" meaning light and "-graph" meaning
> recording. Whether the recording was made photochemically and stored on
> physical media or photoelectrically and stored on digital media is really
> inconsequential to its status as a photograph.
>
> Ken


No. it means (literally) light writing, i.e., as in physically
drawing with light.

Digital sensors produce data.

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> Not a Kodak publication. Also, a film with lesser sensitivity
> (i.e., a slower film) would in fact represent a higher number
> of equivalent pixels due to the finer grain and resolving
> ability. As noted, in comparisons of typical machine 4x6 prints
> from ISO 400 film and digital imagers, all that is needed to
> satisfy the human perception of image quality is 6mp. But the
> fact remains 35mm film exceeds this limited requirement.

Lower resolution didn't stop the CDs from becoming a standard.
Same thing will happen to photography.
Digital is not at its best yet. Half my family is into professional
photography. My grandfather opened his first photo studio in 1928 and my
great-grand-father had a photo studio too.
http://www.mhf.krakow.pl/wystawy/bielec/
http://www.foto-bielec.art.pl/
(sorry the links are not in english)
So, when my aunt or my cousin tells me that she sees a difference between
the film and the digital, I believe them. This is what they do for living.
Still, it doesn't stop them from integrating the digital into their work. As
they both know that it is the future and you need to be able to take
advantage of it if you want to stay in the business.

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In article <4182A636.6840EF5E@aol.com>,
Tom Phillips <nospam777@aol.com> wrote:
>
>
>Chris Brown wrote:
>>
>> In article <26k952-5k8.ln1@narcissus.dyndns.org>,
>> Chris Brown <cpbrown@ntlworld.no_uce_please.com> wrote:
>> >In article <4182032A.D3B720F7@aol.com>,
>> >Tom Phillips <nospam777@aol.com> wrote:
>> >>
>> >>Show me a "multi hour" digital exposure.
>> >
>> >OK, I'll take one tonight and upload it.
>>
>> In the meantime, here's a 30 minute one to be going on with.
>
>30 minutes is not "multi hour."

Reading comprehension not your forte then?

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In article <4182A902.A58F1699@aol.com>,
Tom Phillips <nospam777@aol.com> wrote:
>
>
>Chris Brown wrote:
>>
>> In article <41823255.BC08FE81@aol.com>,
>> Tom Phillips <nospam777@aol.com> wrote:
>>
>> >The questionn is, why is this even a debate?
>>
>> It's not - in the eyes of nearly everyone who regarded this as some kind of
>> "contest", 35mm "lost" years ago, with the previous genertion of DSLRs.
>> You're trotting out the sort of stuff that used to infest r.p.e.35mm and
>> r.p.d about 2-4 years ago. Pretty much everyone else has accepted reality
>> and moved on.

[snip more assertions in conflict with observed reality]

>> >For _pictorial_ imaging, film is the better medium. The
>> >facts bear this out.
>>
>> I quite agree, you just need the film to be 6cm wide or more to compete
>> in the quality stakes these days.
>
>Well, I shoot 4x5.

Perhaps you'd be happier getting with shooting your 4*5 then - you currently
seem quite obsessed with exaggerating the abilities of small format film.

>It's not what anyone says, it's what the technology actually
>does and doesn't do.

Now you're getting the idea.

Consumer DSLRs and 35mm are both good for A4 prints, and passable for A3
prints of some subjects. That is "what the technology does and doesn't do".
Your mathematics is uninteresting and irrelevant.

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Paul wrote:
>
> > Not a Kodak publication. Also, a film with lesser sensitivity
> > (i.e., a slower film) would in fact represent a higher number
> > of equivalent pixels due to the finer grain and resolving
> > ability. As noted, in comparisons of typical machine 4x6 prints
> > from ISO 400 film and digital imagers, all that is needed to
> > satisfy the human perception of image quality is 6mp. But the
> > fact remains 35mm film exceeds this limited requirement.
>
> Lower resolution didn't stop the CDs from becoming a standard.
> Same thing will happen to photography.

You're right. mediocrity rules.

> Digital is not at its best yet.

Sure. But it is _different_ from film and cannot do the
same things.

> Half my family is into professional
> photography. My grandfather opened his first photo studio in 1928 and my
> great-grand-father had a photo studio too.
> http://www.mhf.krakow.pl/wystawy/bielec/
> http://www.foto-bielec.art.pl/
> (sorry the links are not in english)
> So, when my aunt or my cousin tells me that she sees a difference between
> the film and the digital, I believe them. This is what they do for living.
> Still, it doesn't stop them from integrating the digital into their work. As
> they both know that it is the future and you need to be able to take
> advantage of it if you want to stay in the business.

Digital is a tool. But it cannot replace film because
it's not film.

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

Chris Brown wrote:
>
> In article <4182ACF8.F5A99776@aol.com>,
> Tom Phillips <nospam777@aol.com> wrote:
> >
> >
> >Chris Brown wrote:
> >>
> >> In article <lhsgd.13512$ta5.12299@newsread3.news.atl.earthlink.net>,
> >> Jeremy <jeremy@nospam.thanks.com> wrote:
> >> >
> >> >Kodak quotes 24 MP as the equivalent of 35mm film, on their website.
> >>
> >> Large film manufacturer gives optimistic interpretation of raw data
> >> regarding own product shock! Film at eleven (no pun intended).
> >
> >Quote: "the pixel size of a highly sensitive emulsion layer is
> >assumed to be 100 square micrometers on the basis of the fact
> >that a color film with an ISO 400 sensitivity and 135 format
> >contains 24 million pixels."
>
> What a nonsensical quote - film contains no pixels at all.

The article was writen by a photo scientist, and they
do indeed use comparitive pixels as a measure based
on the number of absorbed photons per area of either
developable grains or pixel-photodetector area.

I view it as merely a comparison of the pictorial information
available. And you're right, film has no pixels. If we
instead measure that information using grains contained, even
a 35mm film has _billions_ more picture "elements" than
any digital sensor.

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

Tom Phillips wrote:
>
> Chris Brown wrote:
>
>>In article <26k952-5k8.ln1@narcissus.dyndns.org>,
>>Chris Brown <cpbrown@ntlworld.no_uce_please.com> wrote:
>>
>>>In article <4182032A.D3B720F7@aol.com>,
>>>Tom Phillips <nospam777@aol.com> wrote:
>>>
>>>
>>>>uh huh... multi-hour digital. And no noise due to heat. right.
>>>>(and heat is *inherent* in digital sensor exposure...)
>>>>
>>>>Show me a "multi hour" digital exposure.
>>>
>>>OK, I'll take one tonight and upload it.
>>
>>In the meantime, here's a 30 minute one to be going on with.
>
> 30 minutes is not "multi hour."

Hence the words "in the meantime". I think he put that one up
to act as a not-quite-what-you-wanted preview of what's to come.

> CMOS sensors are an improvement over CCD sensors.
> But,caveats still exist. For exmaple, it is still
> a fact of electronics that the bigger the pixel the
> better the signal and the less noise.

I think what you're wanting to say is the signal to noise ratio
for larger pixels is often greater than that of smaller pixels,
resulting from the deeper electron well afforded by a larger
sensing area.

> Hours and hours is what you claimed. Noise is still going
> to be an issue. The issue with film is reciprocity failure,
> but this is easily compensated for and there is no noise.
> The fact is, due to Nyquist digital sensors suitable for
> longer exposures simply are not going to match the detail
> and resolution possible with film.

Out of curiosity, do you have a website anywhere that I might
view some high detail low-light pictures you have taken? I'm
considering exploring this area of photography (even though
I'm on the digital side of things) and would like to see what
other folks have accomplished.

BJJB

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

BillyJoeJimBob wrote:
>
> Tom Phillips wrote:
> >
> > Quote: "the pixel size of a highly sensitive emulsion layer is
> > assumed to be 100 square micrometers on the basis of the fact
> > that a color film with an ISO 400 sensitivity and 135 format
> > contains 24 million pixels."
>
> Typical 135 format film measures 36x24 mm, for a total imaging area
> of 864 square mm, or 864,000,000 square microns. Dividing this by
> the quoted pixel size above yields 8,640,000 "pixels" on the 135
> format film. I have no idea how the authors of that quote came up
> with 24 million, which at first glance appears to be too large by
> nearly a factor of three. Perhaps the authors assume some degree of
> overlap between "pixels" on the emulsion layer?


it's based on the number of absorbed photons per area of
developable grains, not the film dimensions. That's what
it says, anyway.

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

[Hm, way too many groups, but I can't decide which ones to remove.]

Kibo informs me that Tom Phillips <nospam777@aol.com> stated that:

>pk wrote:
>>
>> Whats wrong with you? You are making this too complicated. And did you
>> really need to cross post this to half a dozen newsgroups?
>
>I do agree this is should not have been crossposted.
>
>> Digital film (senor) sensitivity are equivalent to film.
>
>Incorrect. CCD or CMOS sensors are not equal to film; one is
>not equivalent to then other. There are differenent physics
>and imaging properties that apply to any giving situation.

Yes, but the end result is quite similar for photographic purposes. In
the context of lattitude/dynamic-range (ie; the OP's problem), the only
important difference is that an electronic image sensor has a brick-wall
cut off at the highlight side of the scale, whereas most people are used
to shooting colour negative film, which is somewhat more forgiving of
highlights. OTOH, a lot of that is more to do with it being reversal
film, because people shooting positive colour film (ie; slide film) also
have to watch out for sharply cut-off highlights as, (although, IIRC,
not quite as sharply as an image sensor).
But leaving aside all the technical details, the fact is that a piece of
film & an image sensor are both devices for trapping photons & keeping
track of how /many/ photons they've trapped. They're both subject to the
same laws of physics in that regard, resulting in similar compromises.

>Film has the ability to _accumulate_ light and endure long
>exposures or multiple exposures that can capture detail
>in the dimmest of situations. Reciprocity failure is the
>only factor. Silicon simply can't do this and is limited by
>both exposure latitude and length of exposure.

That's incorrect. CCD & CMOS sensors accumulate electrons in a charge
well in each pixel. They can be, & often are, used for long exposures of
very dim light sources. As a bonus, their equivalent of reciprocity
failure (charge leakage) can be controlled far more easily than for
film. The tradeoff is that they pick up thermal noise, but in for really
long exposures, the sensor will be cryogenically cooled.

>> The higher
>> the ISO the more sensitive the film is to light. So the higher the ISO
>> on a digital camera the more sentive to light the digital sensor is.
>
>Digital sensors have a _nominal_ "speed" at which they
>produce the best quality image. When you alter that speed
>the image quality goes down.

Um. There's a certain amount of truth to that, but it's not quite so cut
& dried as you are implying. The 'inherent' speed (actually sensitivity)
of a CCD/CMOS sensor is a function of a number of design factors, such
as the size of the charge well & photo-sensitised area at each pixel,
how much light is lost to the CFA (if one is used), the accuracy &
signal-to-noise ration of the sense amps, resolution/sensitivity of the
A2D converter(s), whether microlenses are used, the amount of noise
considered acceptable for the sensors intended use, etc. All of those
variables determine the maximum usable sensitivity of a particular
sensor, certainly, but that's equally true of the way a particular film
emulsion is formulated as well.

> Film can be rated at a different
>speeds and still produce quality results because as development
>of film is altered, effective speed also alters. Also, a "slow"
>film can be simply be exposed for a longer time than a faster
>film, and achieve the same results. No loss in image quality.

You don't think that reciprocity failure counts as "loss of quality"? -
I certainly do!

>Film can be exposed for hours. Try that with a digital sensor.
>It simply one of the differences between these two imaging
>mediums.

Well no, it's the difference between standard film & the design goals
for digital cameras sold to the general public. There is no inherent
limitation to semiconductor image sensors that makes it impossible to
design one suitable for multi-hour exposures - there's just not a very
big market for such sensors. (That said, try Googling for information on
the kinds of image sensors used for astronomy - it's fascinating what
you can do with a CCD if you're willing to spend enough money.)

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

Kibo informs me that Tom Phillips <nospam777@aol.com> stated that:

>Tom Phillips wrote:
>
>> That's the point. If the OP wants to obtain detail in nighttime
>> exposures, he might try using a suitable film and employing
>> a multiple exposure technique. No digital camera can do this.
>
>Either that or he should stop crossposting...

Gotcha, troll.

Forgot to change ID's before responding to your sock-puppet, eh?


[For everyone reading this thread, you're being trolled by this idiot.
He's trying to start up yet another of those interminable film/digital
flamewars. Too bad he screwed up while switching personas.]

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

In article <4182C8B8.CDAEB46E@aol.com>,
Tom Phillips <nospam777@aol.com> wrote:
>
>> >Quote: "the pixel size of a highly sensitive emulsion layer is
>> >assumed to be 100 square micrometers on the basis of the fact
>> >that a color film with an ISO 400 sensitivity and 135 format
>> >contains 24 million pixels."
>>
>> What a nonsensical quote - film contains no pixels at all.
>
>The article was writen by a photo scientist,

I don't care if it was written by the Tooth Fairy, it's still nonsense.

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

In article <10o62mqhd9bhnc0@news.supernews.com>, "jjs" <jjs@x.x.com>
wrote:

> Tom P seems to be stuck in an indefensible position. If I were him I'd
> change my name to.... what is appropriate... BLANK, yes, that's an
> appropriate name.

Your wrong you idiot, and that just shows what you know,... zip zilch nada.
Several appropriate names come to mind for you, however. JJ Ass. Staffacoccus?
--
LF Website @ http://members.verizon.net/~gregoryblank

"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

Archived from groups: alt.comp.periphs.dcameras,rec.photo.digital,rec.photo.equipment.35mm,rec.photo.film+labs,rec.photo.darkroom (More info?)

BJ wrote:
>
> what a load of waffle!
> I suppose with Digital we must have dispensed with photons

photoelectrons, dummy...Digital is photoelectric.


> and we don't get
> a representation of the intensity and frequency?
> It matter nothing whether we obtain a sample of the data (the source is
> data!) via chemical means or via sensor for your classification. In essence,
> and as part of the fundamentals of Physics they are analogous.
> As far as your continual reference to "The Nyquist" you make it sound as if
> you have stumbled across some incredible, mostly understood phenomenon that
> restricts Digital signal analysis and can therefore be used as a
> justification for tossing out Digital Photography. Have you ever actually
> done any digital signal sampling and processing? I doubt it! Even by the way
> you use the term it shows you have little knowledge of it.
> I can't wait until you hear of a Cepstrum!
>
> "Tom Phillips" <nospam777@aol.com> wrote in message
> news:4182AD9B.B7007F9A@aol.com...
> >
> >
> > Ken Alverson wrote:
> >>
> >> "Tom Phillips" <nospam777@aol.com> wrote in message
> >> news:41823255.BC08FE81@aol.com...
> >> >
> >> > Photography produces a photograph. And a photograph is an
> >> > image written on photosensitive materials by the direct
> >> > action of light. Digital imaging is electronic and about
> >> > as "photographic" as your television cameraman broadcasting
> >> > to your T.V. set. Again, no photograph.
> >>
> >> Photograph, from the greek "photo-" meaning light and "-graph" meaning
> >> recording. Whether the recording was made photochemically and stored on
> >> physical media or photoelectrically and stored on digital media is really
> >> inconsequential to its status as a photograph.
> >>
> >> Ken
> >
> >
> > No. it means (literally) light writing, i.e., as in physically
> > drawing with light.
> >
> > Digital sensors produce data.