PDA

View Full Version : Digital vs. Film in Astrophotography


Jason Donahue
December 29th 03, 05:11 AM
Hey all,

OK, this is the first time, in using Usenet for 12 years, I've ever
crossposted, but this seemed like a subject to ask both groups. Right about
now, all the people in r.p.e.35mm are going "Aw, crap, another film vs.
digital thread?" - just wait, everyone, my goal isn't a religious war, and
this isn't simply retreading old ground. Meanwhile, in sci.astro groups,
they're saying, "There's even a question?" - well, that's kind of my whole
point, actually. But, first, some background.

I shoot 35mm SLRs, and have since I was a kid. However, I'll be the first
to admit I never got too deep into the aspects of photography, just using my
camera to shoot family snapshots. I've just begun to learn about the finer
points of film photography, the capabilities of different films, etc. At
the same time, I'm also a newcomer to amateur astronomy, and to
astrophotography, and am a bit confused about

Oceanside Photo & Telescope has a pretty good FAQ on CCD imaging in
astrophotography, which can be found at
http://www.optcorp.com/cart/ProductDetail.asp?PR_ProductID=3048 - it's a bit
long, but a worthwhile read for those not familiar with the current process
used. Essentially, though, the argument is that a CCD, especially one
cooled significantly below ambient temperature (to cut down on noise), is
more light-sensitive, doesn't suffer from reciprocity failure, and there's
more ability for image enhancement of the digital image, not to mention the
whole instant gratification aspect.

OK, so that's the basic argument as to the superiority of digital over film
in astrophotography, and it makes sense. However, is CCD imaging really
that much better? For example, the CCD has to be cooled to cut down on
noise, an issue you don't see with film. Also, the majority of CCDs in use
are smaller than 35mm film format - wouldn't that generally mean poorer
maximum resolution? I mean, some of the better 35mm films give incredible
resolutions, and, combined with 40 megapixel film scanners, you get better
resolution than digital. Also, is reciprocity failure as pronounced on
newer films as it used to be - IIRC, doesn't the new formula for Elite
Chrome 100 go a long way towards solving this? Are there others? And,
wouldn't lower ISO film, while requiring longer exposures, give far better
color saturation as well?

Lastly, what areas of astrophotography is film still advantageous at? Right
now, I'm primarily sticking with wide field, unguided shots (I'll be posting
some new pics once I can borrow my friend's film scanner in a couple days),
doing long-exposure star trails or short exposure shots of constellations,
etc. As I continue to invest, this'd be a major issue, as the types of
equipment start diverging dramatically after a while.

Thanks in advance for any advice you might have. Oh, and, kids, let's try
to keep the flames to a minimum, please, 'kay?

--Jason

Chris L Peterson
December 29th 03, 05:57 AM
On Sun, 28 Dec 2003 21:11:27 -0800, "Jason Donahue"
> wrote:

>OK, so that's the basic argument as to the superiority of digital over film
>in astrophotography, and it makes sense. However, is CCD imaging really
>that much better? For example, the CCD has to be cooled to cut down on
>noise, an issue you don't see with film.

Does that matter? A digital camera designed for long exposures _is_ cooled, so
it is that cooled camera you are comparing to film.


>Also, the majority of CCDs in use
>are smaller than 35mm film format - wouldn't that generally mean poorer
>maximum resolution?

It depends on your ability to match your optics to your imager/film. CCDs (with
pixels in the 5-10um range) are higher resolution than most films at the focal
plane.


>I mean, some of the better 35mm films give incredible
>resolutions, and, combined with 40 megapixel film scanners, you get better
>resolution than digital.

There are very few films that (in 35mm format) deliver anything close to 40
megapixels. At best, typical color films used by most astrophotographers can
yield spatial data at around 5-10 megapixels, and that varies with contrast. The
MTF for a digital sensor is flat, so you get uniform response regardless of
contrast. Since film is non-linear and doesn't have much dynamic range, you have
to deal with much lower intensity resolution.


> Also, is reciprocity failure as pronounced on
>newer films as it used to be - IIRC, doesn't the new formula for Elite
>Chrome 100 go a long way towards solving this?

Yes.


> And,
>wouldn't lower ISO film, while requiring longer exposures, give far better
>color saturation as well?

Color film (and color sensors, for that matter) are highly inferior for
astroimaging. If you want accurate color and first rate results, you need to use
three filter imaging on B&W media.


>Lastly, what areas of astrophotography is film still advantageous at?

I think all that is left is economics. If you want to do a combination of wide
field and high resolution, film is way cheaper. But I'm talking medium format
here. If you are imaging with 35mm color film, I think that you can do as well
with a $1000 digital camera like the 300D.


> Right
>now, I'm primarily sticking with wide field, unguided shots (I'll be posting
>some new pics once I can borrow my friend's film scanner in a couple days),
>doing long-exposure star trails or short exposure shots of constellations,
>etc. As I continue to invest, this'd be a major issue, as the types of
>equipment start diverging dramatically after a while.

I expect the market for film cameras to be essentially wiped out by digital
cameras over the next few years. That means film will be relegated to a
specialty market, much smaller than today's. That may make the development of
new emulsion chemistries a thing of the past. The range of films available, and
the rate that new ones are developed, may become very limiting to
astrophotographers in the near future.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Mike Fitterman
December 29th 03, 06:10 AM
All I can say is take a look at these 2 shots. Look at the time spent
taking them and how easy it was for him to get it right (granted he's spent
a while learning how).

http://www.astro-nut.com/m31.html

http://www.astro-nut.com/m42-03dec25.html

These are simply incredible and I can't imagine needing any more resolution
(although if I can get it I'd take it :-)

I can't imagine having to wait to see if my shots came out and have to wait
for another clear night to do it all over again!

Mike.

Robert Meyers
December 29th 03, 08:40 AM
"Chris L Peterson" > wrote in message
...
> It depends on your ability to match your optics to your imager/film. CCDs
(with
> pixels in the 5-10um range) are higher resolution than most films at the
focal
> plane.

If you buy good film, and keep with good optics, you end up starting where
the best of these CCDs get too. Especially for wide feild. No real reason
you shouldn't equal or match, hell, pretty much all the film I use day in
and day out does. Hell, most film starts at 100 line pairs per millameter,
or 5um. That is a starting point. You can actually get well below that,
with some B&W getting down to .69um (720 lpmm) or smaller. Hosw would CCDs
have higher resolution?


> There are very few films that (in 35mm format) deliver anything close to
40
> megapixels. At best, typical color films used by most astrophotographers
can
> yield spatial data at around 5-10 megapixels, and that varies with
contrast. The
> MTF for a digital sensor is flat, so you get uniform response regardless
of
> contrast. Since film is non-linear and doesn't have much dynamic range,
you have
> to deal with much lower intensity resolution.

Are most Astrophotgraphers using older types of film, or are they possibly
processing them in such a way that degrades their performance? 40 MP is not
actually near the limits of current 100 ISO films, which makes this really
odd sounding. Are you thinking like 1600 ISO?

Interesting outlook on the future of film. As a lower end film camera still
blows the highest end digital out of the water for resolution, I do not
believe film is doomed.

Thanks for the info.

Terry B
December 29th 03, 10:50 AM
"Robert Meyers" > wrote in message
...
>
> "Chris L Peterson" > wrote in message
> ...
> > It depends on your ability to match your optics to your imager/film.
CCDs
> (with
> > pixels in the 5-10um range) are higher resolution than most films at the
> focal
> > plane.
>
> If you buy good film, and keep with good optics, you end up starting where
> the best of these CCDs get too. Especially for wide feild. No real
reason
> you shouldn't equal or match, hell, pretty much all the film I use day in
> and day out does. Hell, most film starts at 100 line pairs per
millameter,
> or 5um. That is a starting point. You can actually get well below that,
> with some B&W getting down to .69um (720 lpmm) or smaller. Hosw would
CCDs
> have higher resolution?

Dear Robert
The resolution of the film is not really that important. If the maximum
resolution of the image at the focal plane is comparable with the size of a
CCD pixel then there is no advantage to having smaller pixels. It is just
oversampling. The resolution is determined by the diameter of the optics,
their quality, the wavelength being looked at and the seeing of the night.
Using finer resolution suffers from the same problem as using too higher
magnification visually. It just magnifies the blur. My CCD has 9um pixels
and there is no way I can get a star less than 4 pixels wide. Using film
won't improve my resolution. Where film still wins is on widefield images
..This is why the 1.2m UK Schmidt telescope still used plates covering 4 deg
of sky and even this is on the way out.

Terry B
Moree
Australia



>
>
> > There are very few films that (in 35mm format) deliver anything close to
> 40
> > megapixels. At best, typical color films used by most astrophotographers
> can
> > yield spatial data at around 5-10 megapixels, and that varies with
> contrast. The
> > MTF for a digital sensor is flat, so you get uniform response regardless
> of
> > contrast. Since film is non-linear and doesn't have much dynamic range,
> you have
> > to deal with much lower intensity resolution.
>
> Are most Astrophotgraphers using older types of film, or are they possibly
> processing them in such a way that degrades their performance? 40 MP is
not
> actually near the limits of current 100 ISO films, which makes this really
> odd sounding. Are you thinking like 1600 ISO?
>
> Interesting outlook on the future of film. As a lower end film camera
still
> blows the highest end digital out of the water for resolution, I do not
> believe film is doomed.
>
> Thanks for the info.
>
>

Michael A. Covington
December 29th 03, 03:09 PM
"Robert Meyers" > wrote in message
...

> > There are very few films that (in 35mm format) deliver anything close to
> 40
> > megapixels....
>
> Are most Astrophotgraphers using older types of film, or are they possibly
> processing them in such a way that degrades their performance? 40 MP is
not
> actually near the limits of current 100 ISO films, which makes this really
> odd sounding. Are you thinking like 1600 ISO?

For reciprocity reasons I use Elite Chrome 100 and 200. They are quite
sharp, but remember, the lines/mm rating of film does not translate directly
into pixel resolution. Remember also that the three color layers have
different resolutions.

I routinely digitize my color slides. It works out best to digitize at
about 50 pixels/mm, giving a 2-megapixel image. Believe it or not, this
almost always does justice to the entire slide. Twice that resolution,
giving an 8-megapixel image, certainly does. Beyond that, I won't be
picking up any more picture detail, just film grain.

A good 6-megapixel cooled CCD camera should outperform 35-mm film for
astrophotography. (Bear in mind that for smoothness, you often have to
"bin" the pixels 2x2, which reduces the number of megapixels to a quarter of
what it was; 1.5 in this case.) SBIG has a camera in this range, priced at
$15,000 to $45,000 depending on the grade of CCD. Big observatories have
even bigger ones, up into the 100 megapixel range, but they cost a fortune.

Right now, an SLR body ($100 used) and a roll of film ($10) still beats a
$15,000 CCD camera.

> Interesting outlook on the future of film. As a lower end film camera
still
> blows the highest end digital out of the water for resolution, I do not
> believe film is doomed.

I don't think it's dead yet. Neither is oil painting... :)


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

Michael A. Covington
December 29th 03, 03:14 PM
"Roger Hamlett" > wrote in message
...

> For the highest sensitivity, film needs to be cooled, and hypered.

With the newest-technology color film (e.g., Kodak E100G), this does not
appear to be the case. There is very little reciprocity failure. All the
hypering you need (to get above the "toe" of the curve) can be accomplished
by preflashing.

> The idea of 'instant gratification', probably reflects a misunderstanding
of
> just how much work a CCD image will entail. By the time, you have taken
dark
> frames, flat fields, processed each image with these, and combined the
> components, an evenings work, may allow the final image to be seen.

Right... But you do get "instant feedback" -- an almost instant indication
of whether you're getting something useful.

> Yes modern films do still suffer from reciprocity failure (it is inherent
in
> the chemistry). The improvements generally, have slightly reduced the
> amount, and often massively improved the behaviour across the spectrum.

I would say the reciprocity failure has diminished tremendously. Using
Schwarzschild's formula, the exponent is 1 for a "perfect" film or CCD, 0.95
for the newest color films, and 0.7 for the films of the 1970s.

> I think the only people who would 'flame', would either be 'diehard' film
> users, who want to believe there is no improvement with CCDs (you have to
> wonder why observatories have allmost universally stopped using film...),
or
> CCD users, who have never had the delight of the sort of images that film
> can with care, in the right circumstances produce.

My own feeling is that I want to know how to use all the tools in the kit!


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

Don Stauffer
December 29th 03, 03:25 PM
Ah, but serious astrophotographers DO cool film in film cameras, and do
such fancy things as presensitizing film with various gases and
chemicals.

Jason Donahue wrote:
>
>
> OK, so that's the basic argument as to the superiority of digital over film
> in astrophotography, and it makes sense. However, is CCD imaging really
> that much better? For example, the CCD has to be cooled to cut down on
> noise, an issue you don't see with film. Also, the majority of CCDs in use
> are smaller than 35mm film format - wouldn't that generally mean poorer
> maximum resolution? I mean, some of the better 35mm films give incredible
> resolutions, and, combined with 40 megapixel film scanners, you get better
> resolution than digital. Also, is reciprocity failure as pronounced on
> newer films as it used to be - IIRC, doesn't the new formula for Elite
> Chrome 100 go a long way towards solving this? Are there others? And,
> wouldn't lower ISO film, while requiring longer exposures, give far better
> color saturation as well?
>
>snip
>
> --Jason

--
Don Stauffer in Minnesota

webpage- http://www.usfamily.net/web/stauffer

Davoud
December 29th 03, 04:23 PM
Michael A. Covington:
> ...A good 6-megapixel cooled CCD camera should outperform 35-mm film for
> astrophotography. (Bear in mind that for smoothness, you often have to
> "bin" the pixels 2x2, which reduces the number of megapixels to a quarter of
> what it was; 1.5 in this case.) SBIG has a camera in this range, priced at
> $15,000 to $45,000 depending on the grade of CCD. Big observatories have
> even bigger ones, up into the 100 megapixel range, but they cost a fortune.

"A fortune" is quite relative. I'm trying to imagine myself telling my
wife -- aka "the breadwinner" -- that I want to spend $15-$45k on a CCD
camera. "You've been raving about the F3 that you bought on Ebay. All
of a sudden it's no good and you want to spend a fortune on a CCD
camera?"

> Right now, an SLR body ($100 used) and a roll of film ($10) still beats a
> $15,000 CCD camera.

I'll know if this is true for me in a couple of days. I'm about to take
my first roll of Elite Chrome 100 in for processing. (Nikon F3, 200mm
Nikkor/piggyback). I do my commercial and personal stuff with digital
cameras, and I had practically forgotten what it's like to be anxious
for transparencies to come back!

Davoud

--
usenet *at* davidillig dawt com

Chris L Peterson
December 29th 03, 04:57 PM
On Mon, 29 Dec 2003 00:40:37 -0800, "Robert Meyers" >
wrote:

>If you buy good film, and keep with good optics, you end up starting where
>the best of these CCDs get too. Especially for wide feild. No real reason
>you shouldn't equal or match, hell, pretty much all the film I use day in
>and day out does. Hell, most film starts at 100 line pairs per millameter,
>or 5um. That is a starting point. You can actually get well below that,
>with some B&W getting down to .69um (720 lpmm) or smaller. Hosw would CCDs
>have higher resolution?

100 lp/mm is _not_ equivalent to 5um pixels on a digital sensor. Indeed, the
lp/mm spec of film is nearly worthless. Look instead at the MTF curve for the
film (if it is available!). The actual resolution is highly dependent on
contrast. Ektachrome 200, for example, (a very popular film for
astrophotography) has a resolution as low as 6 lp/mm for contrasty objects! Most
color 35mm films are oversampled when scanning them at 2K x 3K, which
corresponds to 12u pixels. In tests I have made with several color films, the
film doesn't actually start behaving like a CCD until you treat it as having
20u-50u virtual pixels.


>Are most Astrophotgraphers using older types of film, or are they possibly
>processing them in such a way that degrades their performance? 40 MP is not
>actually near the limits of current 100 ISO films, which makes this really
>odd sounding. Are you thinking like 1600 ISO?

No, I'm thinking of things like the newer Provia and Gold emulsions. I've got
professional drum scans made at 40 MP. In resolution, they are indistinguishable
from a 6 MP scan from a desktop film scanner. You can also resample the 40 MP
down to 6 MP and see that no real information is lost.


>Interesting outlook on the future of film. As a lower end film camera still
>blows the highest end digital out of the water for resolution, I do not
>believe film is doomed.

I hope not. But since the images I'm seeing from 6 MP digital cameras (in my
eyes) are equivalent to the best I'm seeing from 35mm film, I obviously disagree
with your assessment. I suspect your view represents a minority one. There are
still people who think tube amplifiers sound better, or that vinyl discs sound
better. It doesn't matter whether they are right or wrong, it only matters that
they represent a very small part of the audio market, and anyone can see what
that has done to prices and new developments. I'm only suggesting that I think
it likely the same thing will happen with film.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Del Johnson
December 29th 03, 07:22 PM
Chris,

You have it backwards. Because film is nonlinear, it has a greater dynamic
range than a CCD. Don't confuse range with sensitivity. CCDs are more
prone to oversatuation than film. For example, a single unprocessed
exposure of the Orion Nebula will turn out better on film that on a CCD with
regard to dynamic range.

Also, the original poster meant to say that film has more definition rather
than more resolution. Definition is the pixel count (like HDTV); resolution
is the pixel size coupled with optical performance.

Del Johnson



"Chris L Peterson" > wrote in message
...
> On Sun, 28 Dec 2003 21:11:27 -0800, "Jason Donahue"
> > wrote:
>
> >OK, so that's the basic argument as to the superiority of digital over
film
> >in astrophotography, and it makes sense. However, is CCD imaging really
> >that much better? For example, the CCD has to be cooled to cut down on
> >noise, an issue you don't see with film.
>
> Does that matter? A digital camera designed for long exposures _is_
cooled, so
> it is that cooled camera you are comparing to film.
>
>
> >Also, the majority of CCDs in use
> >are smaller than 35mm film format - wouldn't that generally mean poorer
> >maximum resolution?
>
> It depends on your ability to match your optics to your imager/film. CCDs
(with
> pixels in the 5-10um range) are higher resolution than most films at the
focal
> plane.
>
>
> >I mean, some of the better 35mm films give incredible
> >resolutions, and, combined with 40 megapixel film scanners, you get
better
> >resolution than digital.
>
> There are very few films that (in 35mm format) deliver anything close to
40
> megapixels. At best, typical color films used by most astrophotographers
can
> yield spatial data at around 5-10 megapixels, and that varies with
contrast. The
> MTF for a digital sensor is flat, so you get uniform response regardless
of
> contrast. Since film is non-linear and doesn't have much dynamic range,
you have
> to deal with much lower intensity resolution.
>

Del Johnson
December 29th 03, 07:25 PM
Not really. Many color films work just fine uncooled and unhypered. It is
mostly the Tech Pan B&W film that needs the boost.

Del Johnson


"Roger Hamlett" > wrote in message
...
> For the highest sensitivity, film needs to be cooled, and hypered. The
> difference here is unimportant, since an astronomical CCD, will have the
> cooling built in.

Chris L Peterson
December 29th 03, 07:59 PM
On Mon, 29 Dec 2003 11:22:01 -0800, "Del Johnson" <[email protected]{right star in
Orion's belt}.sdsu.edu> wrote:

>Chris,
>
>You have it backwards. Because film is nonlinear, it has a greater dynamic
>range than a CCD. Don't confuse range with sensitivity. CCDs are more
>prone to oversatuation than film. For example, a single unprocessed
>exposure of the Orion Nebula will turn out better on film that on a CCD with
>regard to dynamic range.

I don't have it backwards at all. At the ends of the "S" curve you get with film
the range is compressed down to the noise level. A decent CCD detector will have
between 10 and 50 times the dynamic range of a good film.

Yes, a single exposure on the film may turn out "better" because the film is
compressing the range- that is, you are losing information at the top and
bottom. IMO that is not an advantage; I see how some might see it that way,
though.


>Also, the original poster meant to say that film has more definition rather
>than more resolution. Definition is the pixel count (like HDTV); resolution
>is the pixel size coupled with optical performance.

Yes, the terminology is a problem here. Different disciplines use the same words
in quite different ways. In terms of pixel count, I'd say that a typical 35mm
color film is somewhere between 2 MP and 10 MP, depending heavily on the
characteristics of the image. A typical CCD these days is between 1 MP and 4 MP,
but without the dependence on the image. So the spatial information content
isn't all that different between the two, and CCDs are rapidly becoming higher
density devices.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Alan Browne
December 29th 03, 08:30 PM
>>For the highest sensitivity, film needs to be cooled, and hypered. The
>>difference here is unimportant, since an astronomical CCD, will have the
>>cooling built in.


An engineer I knew who was into astrophotography used to cool his B&W
film and then in the 30 minutes before loading it into the camera would
HEAT it to about 45C...he built a very small regulated oven for the
purpose. If I remember correctly, he claimed this made the film more
sensitive (I would expect noisier as well).

Comments?

Alan

Michael A. Covington
December 29th 03, 10:16 PM
"Davoud" > wrote in message
...
> Michael A. Covington:
> > ...A good 6-megapixel cooled CCD camera should outperform 35-mm film for
> > astrophotography. (Bear in mind that for smoothness, you often have to
> > "bin" the pixels 2x2, which reduces the number of megapixels to a
quarter of
> > what it was; 1.5 in this case.) SBIG has a camera in this range, priced
at
> > $15,000 to $45,000 depending on the grade of CCD. Big observatories
have
> > even bigger ones, up into the 100 megapixel range, but they cost a
fortune.
>
> "A fortune" is quite relative. I'm trying to imagine myself telling my
> wife -- aka "the breadwinner" -- that I want to spend $15-$45k on a CCD
> camera. "You've been raving about the F3 that you bought on Ebay. All
> of a sudden it's no good and you want to spend a fortune on a CCD
> camera?"

I should add that contrary to what people often think, as a book author I am
not rich. I too consider a Nikon F3 to be a luxurious camera. And I use
one. For me, $15k is too much to pay for a car, much less a camera.


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

Michael A. Covington
December 29th 03, 10:19 PM
"Chris L Peterson" > wrote in message
...

> >You have it backwards. Because film is nonlinear, it has a greater
dynamic
> >range than a CCD. Don't confuse range with sensitivity. CCDs are more
> >prone to oversatuation than film. For example, a single unprocessed
> >exposure of the Orion Nebula will turn out better on film that on a CCD
with
> >regard to dynamic range.
>
> I don't have it backwards at all. At the ends of the "S" curve you get
with film
> the range is compressed down to the noise level. A decent CCD detector
will have
> between 10 and 50 times the dynamic range of a good film.

The real problem, as you point out, is that with film, the toe is
compressed. We would rather have the toe be perfectly linear and do our
compression, if any, at the shoulder, because the faintest objects in the
picture are usually the most important. Also, the compressed toe works
against you if you want to stack images or subtract out the sky background.

I seem to recall that CCDs typically have a 12- to 16-bit dynamic range. 12
bits is 12 stops, photographically speaking; film is 9 or 10 stops maximum
when developed normally, much less when processed for high contrast in
astronomy.

macnmotion
December 29th 03, 11:33 PM
Michael A. Covington wrote:

I should add that contrary to what people often think, as a book author I am
> not rich. I too consider a Nikon F3 to be a luxurious camera. And I use
> one. For me, $15k is too much to pay for a car, much less a camera.
>


That's a shame. It's a good book and you deserve to be rich. macnmotion

Chris L Peterson
December 29th 03, 11:49 PM
On Mon, 29 Dec 2003 17:19:40 -0500, "Michael A. Covington"
> wrote:

>I seem to recall that CCDs typically have a 12- to 16-bit dynamic range. 12
>bits is 12 stops, photographically speaking; film is 9 or 10 stops maximum
>when developed normally, much less when processed for high contrast in
>astronomy.

The sensors in most commonly used cameras have dynamic ranges of 76-78dB, or
about 13 bits. A couple of cameras are as high as 85dB (14 bits); that's as high
as any sensors I'm aware of amateurs using. There are some tradeoffs. If you
really want a lot of pixels (11M) for not too much money, you could go with the
SBIG STL-11000M, but then you get a sensor with rather poor performance: only 11
bits of dynamic range, shallow pixels, poor linearity, and microlenses. Of
course, with a linear detector, you can just take more pictures- every time you
double the number it is like you added another 6dB, or one stop. This kind of
stacking is very imperfect when applied to film, because you've already lost the
information down at the low intensity end of the range, and because adding
non-linear frames just makes things less linear.

It is important to remember that lots of pixels (or the film equivalent) is
really only important for wide field imaging. For the vast majority of DSOs, one
or two million pixels is more than enough to reach the point where the seeing
and optics are the limiting factor, not the sensor pixel count.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Michael A. Covington
December 30th 03, 12:37 AM
"macnmotion" > wrote in message
...
> Michael A. Covington wrote:
>
> I should add that contrary to what people often think, as a book author I
am
> > not rich. I too consider a Nikon F3 to be a luxurious camera. And I use
> > one. For me, $15k is too much to pay for a car, much less a camera.
>
> That's a shame. It's a good book and you deserve to be rich. macnmotion

Persuade a million of your friends to buy my books and I will be :) :)

Actually I should be careful about saying "I'm not rich" because I've
recently come across people who really look down on me for not being rich.
This is a value system that I don't understand. But right now, with
daughters in and approaching college, I'm not going for high-budget
equipment.

Anyhow, the audience for my books is primarily people with common equipment,
so if I bought really high-end gear, I'd actually become less qualified for
the writing that I do. My main endproduct is not astrophotos -- it's
knowledge of how to make astrophotos.

Thank you for your support!

Michael

Jack Schmidling
December 30th 03, 03:54 PM
Don Stauffer

> Ah, but serious astrophotographers DO cool film in film cameras, and do
> such fancy things as presensitizing film with various gases and
> chemicals.....

Hypersensitizing yes but I think you will have to dig very deep to
find anyone cooling film cameras these days.

In the days before TechPan, cooled cameras were a must but I think
everyone getting into astrophotography since than is mighty glad they
don't have to deal with cooling.

I would be interested in knowing who, if anyone, has any info on
cooling TechPan and if it helps much.

One more point while I am at it, browsing this thread I have not seen
any mention of film grain size.. just a lot of converted electonic
jargon. If anyone has ever looked at a piece of film under a
microscope and then looked at a CCD chip, the argument about
resolution would be pretty moot.

Authors in older books make all sorts of strange claims for the grain
size in film but if you look at the grain under a microscope, you will
realize how shaky these statements are. The pixel is a well defined
rectangle while the film grain looks like a blob of jellow running
down a wall and is sigficantly larger to boot.

Take a half inch square of a film photo and fill you monitor with it
and you will get the idea. CCD resolution is vastly better.

Keep an eye on my web site and see how the old film phots get replaced
by CCD images as time goes by.

js

PHOTO OF THE WEEK... http://schmidling.netfirms.com/weekly.htm

Michael A. Covington
December 30th 03, 04:20 PM
"Jack Schmidling" > wrote in message
m...
> Don Stauffer
>
> > Ah, but serious astrophotographers DO cool film in film cameras, and do
> > such fancy things as presensitizing film with various gases and
> > chemicals.....
>
> Hypersensitizing yes but I think you will have to dig very deep to
> find anyone cooling film cameras these days.
>
> In the days before TechPan, cooled cameras were a must but I think
> everyone getting into astrophotography since than is mighty glad they
> don't have to deal with cooling.
>
> I would be interested in knowing who, if anyone, has any info on
> cooling TechPan and if it helps much.

I researched this a few years ago... It has been shown that most cooled
cameras were too cold. Cooling the film too much reduces the speed.

Cooling hypered Tech Pan should not help, for the simple reason that once
the reciprocity failure is near zero, there's not much possibility of
lowering it any further. At some point you get very close to zero
reciprocity failure, and there you stay.

Ditto for new-technology color films that already have little reciprocity
failure.

Cooling worked miracles with one generation of color films, back in the
1970s. Films have changed.

> Authors in older books make all sorts of strange claims for the grain
> size in film but if you look at the grain under a microscope, you will
> realize how shaky these statements are. The pixel is a well defined
> rectangle while the film grain looks like a blob of jellow running
> down a wall and is sigficantly larger to boot.

What I think you're getting at is that the film grain is *irregular* -- you
will see granularity in a film image even when you're not near the
resolution limit, because of random large-scale variations. In a digital
image, you do not see granularity until you approach the actual resolution
limit.

Keep up the good work!


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

Robert Berta
December 30th 03, 10:17 PM
I have sort of a different view of this issue. I own a professional
photo studio and lab (film based) and am also an avid
astrophotographer. I use both film and CCD and find that each has its
own strong points. While I don't do commercial CCD photo work in my
business (mostly all medium and large format film work)...it is very
obvious that film will soon be a very limited market. The convenience
of digital for Joe average is an easy sell for the convenience,
cross-platform ability (can be printed on home color printers, saved
on computer storage media, etc.) You can also email pics to your
friends. That being said...film for THAT purpose still has the edge in
quality, etc. but only when processed by good labs and knowledgeable
technicians. The average suff you get from the one hour labs is pretty
poor quality and the average digital photo printed out on your $200
color printer at home will likely be better! But film is quickly
dissappearing as CCD is leapfroging with the latest innovations. Even
the traditional film areas like large format photography are changing
over to digital. Of course this isn't cheap...it isn't unusual for a
CCD back for a large format camera ALONE to run over $35,000. This
doesn't include the huge overhead in very high end computers and
computer storage...and large format computer color printers.

The bottom line is that as film becomes more and more of a dead end
media for the masses...you can count on good films suitable for
astrophotography to also go away.

The other differences are that in film there is about a 5% efficiency
ratio...5% of the photons hitting the film are saved. In CCD there is
about a 95% efficiency ratio. This accounts for the greater
sensitivity of a CCD. In addition the response on CCD is lineal or
nearly flat in response. On film even the best ones still have
reciprocity failure...doubling the exposure won't give twice the
photons....you need a longer exposure. This last is probably the main
reason scientists prefer CCD....CCD is lineal...twice the exposure
time doubles the photons captured. From a science standpoint that is a
huge advantage.

And yes...I prefer CCD for astronomy....although I still use film for
wide field imaging. Big chip cameras suitable for covering a wide FOV
and maintaining a favorable sampling ratio are still too
expensive...but they are getting cheaper. However I see the consumer
type big chip digital cameras like the Canons replacing the dedicated
CCD astronomy specific cameras for the average person in a short time.
However, the better IR and blue response and lower noise of a CCD
camera designed for astronomy will still be the instrument of choice
for serious scientists and advanced amateurs for a long time.

Bob Berta

David Littlewood
December 30th 03, 11:19 PM
In article >, Robert
Berta > writes
>
>The other differences are that in film there is about a 5% efficiency
>ratio...5% of the photons hitting the film are saved. In CCD there is
>about a 95% efficiency ratio. This accounts for the greater
>sensitivity of a CCD. In addition the response on CCD is lineal or
>nearly flat in response. On film even the best ones still have
>reciprocity failure...doubling the exposure won't give twice the
>photons....you need a longer exposure.

Film reciprocity failure does not quite work the way you suggest. It's
not that "twice the exposure doesn't mean twice the photons": it's more
a case of "half the rate of photons per second gives less than half the
nucleus sites". This is because (simplifying a complex situation
somewhat) a stable nucleus site requires several Ag atoms, which in turn
requires several (typically 3) photons to create. If a single Ag atom is
left alone for too long before being joined by others it will be lost
and no "exposure" is registered. At "normal" light levels this is
unlikely to happen, but as the level reduces it becomes more probable.

Twice the exposure always (even in the region of severe reciprocity
failure) results in twice the recorded density, as long as you are in
the linear area of the film's characteristics; it just may not be as
much density (for either length of time) as you expected.
--
David Littlewood

Del Johnson
December 30th 03, 11:21 PM
It is this "compression" that gives film greater range. The CCD may
distinguish more levels of brightness, and is certainly more sensitive, but
film prevails when there is a large difference between bright and dark
objects in the same image.

Why would this not be an advantage? The alternative is a complete loss of
detail in the oversaturated areas.

Del Johnson



"Chris L Peterson" > wrote in message
...
>
> Yes, a single exposure on the film may turn out "better" because the film
is
> compressing the range- that is, you are losing information at the top and
> bottom. IMO that is not an advantage; I see how some might see it that
way,
> though.
>
>

Chris L Peterson
December 31st 03, 06:27 AM
On Tue, 30 Dec 2003 15:21:14 -0800, "Del Johnson" <[email protected]{right star in
Orion's belt}.sdsu.edu> wrote:

>It is this "compression" that gives film greater range. The CCD may
>distinguish more levels of brightness, and is certainly more sensitive, but
>film prevails when there is a large difference between bright and dark
>objects in the same image.
>
>Why would this not be an advantage? The alternative is a complete loss of
>detail in the oversaturated areas.

It's not an advantage because you pay for your lack of saturation at the bright
end with a huge loss of detail at the dim end (everything is compressed into a
very narrow brightness range). It is precisely in the ability to show detail at
the dim, low contrast end of things where CCDs shine, and that is the region
that is usually of the most interest (to me, anyway) when examining astronomical
objects.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Del Johnson
December 31st 03, 06:08 PM
Sounds like you are still confusing range with sensitivity. It is a given
that a CCD will pick up fainter objects for the same integration. If one
adjusts the integration time so that the faint range is about the same
between film and CCD, one will find that film will be less likely to
overexpose the brighter portions of the image.

Any single unprocessed CCD of the Orion Nebula that shows the fainter wisps
will completely burn out the bright core, whereas a film image will do a
better job of capturing the entire dynamics of this object (albeit with a
longer exposure). The only good images of the Orion Nebula with a CCD are
a result of multiple stacked images or mosaics that have been pumped up with
paint software.

Del Johnson


"Chris L Peterson" > wrote in message
...
>>
> It's not an advantage because you pay for your lack of saturation at the
bright
> end with a huge loss of detail at the dim end (everything is compressed
into a
> very narrow brightness range). It is precisely in the ability to show
detail at
> the dim, low contrast end of things where CCDs shine, and that is the
region
> that is usually of the most interest (to me, anyway) when examining
astronomical
> objects.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com

Chris L Peterson
December 31st 03, 06:46 PM
On Wed, 31 Dec 2003 10:08:49 -0800, "Del Johnson" <[email protected]{right star in
Orion's belt}.sdsu.edu> wrote:

>Sounds like you are still confusing range with sensitivity.

Not at all. Sensitivity is a whole separate issue, and I'm not discussing it at
all.


>Any single unprocessed CCD of the Orion Nebula that shows the fainter wisps
>will completely burn out the bright core, whereas a film image will do a
>better job of capturing the entire dynamics of this object (albeit with a
>longer exposure).

You are fooling yourself here. Most film has an overall dynamic range of about
3A, or maybe 3.5A if you really push out into the extremely non-linear portion
of the response curve (that is, where a factor of 10 difference in source
intensity produces essentially the same density on the film). Most CCDs have an
overall dynamic range of about 78dB, or 3.9A, and that is nearly linear end to
end. The simple fact is that if you make a single CCD exposure of the Orion
nebula adjusted just to the point where the core is about to saturate, you will
have captured more detail at the wispy edges than the film image will give you
assuming that you expose it long enough to compensate for the difference in
sensitivity.

The trick with film is that you can expose it even longer than that in order to
bring some of the wispy detail up on the image, and still have a reasonable
looking core. But even so, that core has been pushed up onto the flat part of
the response curve, which means that much of the structural detail has been
obliterated, even if it doesn't have the characteristic blown-out appearance of
a saturated CCD image.


> The only good images of the Orion Nebula with a CCD are
>a result of multiple stacked images or mosaics that have been pumped up with
>paint software.

I think this is a bit of an exaggeration, but if not, so what? In what way is
taking multiple CCD images a problem? There is virtually no difference in effort
between taking one CCD image or taking several, and the overall exposure time is
still shorter with the CCD. So if the normal CCD technique involves collecting
and stacking several images, so be it. This is neither an advantage nor a
disadvantage compared with film.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Jose Suro
December 31st 03, 08:06 PM
Talking about Orion - here's a film Orion - a stacked composite. Technique
are the same on software. Well exposed film has a very good range.

Take Care,

JAS


"Chris L Peterson" > wrote in message
...
> On Wed, 31 Dec 2003 10:08:49 -0800, "Del Johnson" <[email protected]{right star in
> Orion's belt}.sdsu.edu> wrote:
>
> >Sounds like you are still confusing range with sensitivity.
>
> Not at all. Sensitivity is a whole separate issue, and I'm not discussing
it at
> all.
>
>
> >Any single unprocessed CCD of the Orion Nebula that shows the fainter
wisps
> >will completely burn out the bright core, whereas a film image will do a
> >better job of capturing the entire dynamics of this object (albeit with a
> >longer exposure).
>
> You are fooling yourself here. Most film has an overall dynamic range of
about
> 3A, or maybe 3.5A if you really push out into the extremely non-linear
portion
> of the response curve (that is, where a factor of 10 difference in source
> intensity produces essentially the same density on the film). Most CCDs
have an
> overall dynamic range of about 78dB, or 3.9A, and that is nearly linear
end to
> end. The simple fact is that if you make a single CCD exposure of the
Orion
> nebula adjusted just to the point where the core is about to saturate, you
will
> have captured more detail at the wispy edges than the film image will give
you
> assuming that you expose it long enough to compensate for the difference
in
> sensitivity.
>
> The trick with film is that you can expose it even longer than that in
order to
> bring some of the wispy detail up on the image, and still have a
reasonable
> looking core. But even so, that core has been pushed up onto the flat part
of
> the response curve, which means that much of the structural detail has
been
> obliterated, even if it doesn't have the characteristic blown-out
appearance of
> a saturated CCD image.
>
>
> > The only good images of the Orion Nebula with a CCD are
> >a result of multiple stacked images or mosaics that have been pumped up
with
> >paint software.
>
> I think this is a bit of an exaggeration, but if not, so what? In what way
is
> taking multiple CCD images a problem? There is virtually no difference in
effort
> between taking one CCD image or taking several, and the overall exposure
time is
> still shorter with the CCD. So if the normal CCD technique involves
collecting
> and stacking several images, so be it. This is neither an advantage nor a
> disadvantage compared with film.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>

Chris L Peterson
December 31st 03, 08:23 PM
On Wed, 31 Dec 2003 20:06:54 GMT, "Jose Suro" > wrote:

>Talking about Orion - here's a film Orion - a stacked composite. Technique
>are the same on software. Well exposed film has a very good range.

No link? But anyway, don't mistake me- I'm not saying that it isn't possible to
get excellent results with film. People have done so for years, and with the
increased use of tricolor filter imaging on B&W film have done even better. It's
just that in a side-by-side comparison between digital and film imaging, I'm
hard pressed to think of any way in which film is better other than cost per
square inch of detector.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Jose Suro
December 31st 03, 09:43 PM
Sorry about the link! I was on the phone and thought I had copied it.

http://astrosurf.com/lorenzi/images/m42.htm

I think 35mm film doesn't have any advantage over CCD other than cost - but
that's a big one. Also, starting with film and moving to CCD is a good way
to get your feet wet before spending the megabucks. Film can't compare with
CCD in sensitivity. I still use it though, because I find the color
saturation of film and the smaller stars appealing.

Happy New Year!

JAS


"Chris L Peterson" > wrote in message
...
> On Wed, 31 Dec 2003 20:06:54 GMT, "Jose Suro" >
wrote:
>
> >Talking about Orion - here's a film Orion - a stacked composite.
Technique
> >are the same on software. Well exposed film has a very good range.
>
> No link? But anyway, don't mistake me- I'm not saying that it isn't
possible to
> get excellent results with film. People have done so for years, and with
the
> increased use of tricolor filter imaging on B&W film have done even
better. It's
> just that in a side-by-side comparison between digital and film imaging,
I'm
> hard pressed to think of any way in which film is better other than cost
per
> square inch of detector.
>
> _________________________________________________
>
> Chris L Peterson
> Cloudbait Observatory
> http://www.cloudbait.com
>

Del Johnson
December 31st 03, 11:49 PM
I think that is what I have been saying......

Del Johnson



"Chris L Peterson" > wrote in message
...
>
> The trick with film is that you can expose it even longer than that in
order to
> bring some of the wispy detail up on the image, and still have a
reasonable
> looking core. But even so, that core has been pushed up onto the flat part
of
> the response curve, which means that much of the structural detail has
been
> obliterated, even if it doesn't have the characteristic blown-out
appearance of
> a saturated CCD image.
>

Del Johnson
December 31st 03, 11:52 PM
Thank you! Well put and very nice work.

Del Johnson





"Jose Suro" > wrote in message
. com...
> Sorry about the link! I was on the phone and thought I had copied it.
>
> http://astrosurf.com/lorenzi/images/m42.htm
>
> I think 35mm film doesn't have any advantage over CCD other than cost -
but
> that's a big one. Also, starting with film and moving to CCD is a good
way
> to get your feet wet before spending the megabucks. Film can't compare
with
> CCD in sensitivity. I still use it though, because I find the color
> saturation of film and the smaller stars appealing.
>
> Happy New Year!
>
> JAS

Jose Suro
January 1st 04, 12:53 AM
It's not mine - I wish! It's and example of what's out there, but the
comments stand.

Happy New Year!

JAS

"Del Johnson" <[email protected]{right star in Orion's belt}.sdsu.edu> wrote in
message ...
> Thank you! Well put and very nice work.
>
> Del Johnson
>
>
>
>
>
> "Jose Suro" > wrote in message
> . com...
> > Sorry about the link! I was on the phone and thought I had copied it.
> >
> > http://astrosurf.com/lorenzi/images/m42.htm
> >
> > I think 35mm film doesn't have any advantage over CCD other than cost -
> but
> > that's a big one. Also, starting with film and moving to CCD is a good
> way
> > to get your feet wet before spending the megabucks. Film can't compare
> with
> > CCD in sensitivity. I still use it though, because I find the color
> > saturation of film and the smaller stars appealing.
> >
> > Happy New Year!
> >
> > JAS
>
>
>

William D. Tallman
January 1st 04, 06:25 AM
Robert Berta wrote:

<snip>
> And yes...I prefer CCD for astronomy....although I still use film for
> wide field imaging. Big chip cameras suitable for covering a wide FOV
> and maintaining a favorable sampling ratio are still too
> expensive...but they are getting cheaper. However I see the consumer
> type big chip digital cameras like the Canons replacing the dedicated
> CCD astronomy specific cameras for the average person in a short time.
<snip>

Interesting thread to read through! Learned a lot!

Question: Now that Canon is using CMOS for it's digital battlewagons, given
your comment, it's worth asking what sort of performance CMOS arrays have,
as compared to both film and CCD.

Thanks,

Bill Tallman

Chris L Peterson
January 2nd 04, 03:54 AM
On Wed, 31 Dec 2003 15:49:03 -0800, "Del Johnson" <[email protected]{right star in
Orion's belt}.sdsu.edu> wrote:

>I think that is what I have been saying......

Well, then I guess we are in agreement (but while I think the image posted by
Jose is better than the one you suggested, I think this-
http://www.starrywonders.com/m42new.html - taken with a 10D- is better yet. And
that isn't even a proper astrocamera!

Anyway, I still think the non-linear response of film is a disadvantage. I don't
know why I would want to use film, throwing away intensity detail at one end or
the other according to the whim of the emulsion designer, when for less effort I
can collect linear data and apply a compression curve of _my_ design to it to
bring out the detail of _my_ choice.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Michael A. Covington
January 5th 04, 03:11 PM
"Jack Schmidling" > wrote in message
om...
> "Michael A. Covington"
>
> > Actually my own two best Mars shots are one of each -- one with a
> > traditional CCD (using a "repeat and pick the best" mode on my STV) and
one
> > with ToUCam Pro. Since the ToUCam Pro costs only 1/10 as much, and
gives a
> > color image, and produced a good image with much less work, I consider
it
> > the winner.....
>
> By definition, there can only be one "best" so you need to make a
> choice. However, it still does not prove the point that it wins in
> any scientific sense.
>
> Until or unless someone produces a web cam picture as good or better
> than the best out there,the CCD wins.

I doubt that the same kind of chip will produce substantially different
pictures at the same temperature with different hardware around it!

The one significant variable is the color mask. I would *expect* monochrome
chips with tricolor masks to have an edge over color chips.

Apart from that, this is almost like asking (in the old days) whether a
Canon or a Nikon would take better astrophotos.