Digital vs. Film in Astrophotography

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/ProductD...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

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

"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.

"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.

"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:
...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

"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

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

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.

On Mon, 29 Dec 2003 11:22:01 -0800, "Del Johnson" delastro@{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