Digital quality (vs 35mm): Any real answers?

Gordon Moat wrote:

Toralf wrote:

snip

3. I know that the most common sensors are made up of individual
elements for the read, green and blue channels, arranged in a special
pattern, whose data is somehow interpolated into RGB pixels. But what
exactly does e.g. 6 megapixels mean in that context? Does it mean that
the sensor has (just) 6 million elements, or that data from a higher
number (like 18 or 24 million) is combined into 6 million RGB pixels?

A Bayer pattern is an array of Red, Green, or Blue pixels, often in a repeating
pattern. Most of these Bayer pattern filters are arranged so that there are
twice as many Green pixels as all others. The patent actually dates from around
1978 from Kodak, and the choice of Green dominance was determined then based on
the human eye being able to resolve Green slightly better than Blue or Red.
Again, check out the Fill Factory web site link for more technical information.

more snip

A couple of thoughts about Bayer resolution. For a 6 megapixel sensor, there are
2MP sensitive to red, 2MP sensitive to blue, and 4MP sensitive to green, as Gordon
says. So, a pure red or pure blue image will theoretically be rendered with only
2MP, while a green image will be rendered with 4MP. The saving grace is that in
real life, very few colors are really saturated primary colors. Most are mixtures
of primary colors together with a considerable gray, or luminance' content, and,
just as in televison where the bandwidth allows up to 5 or so MHz of luminance
signal but only about 1 MHz of color signal, the luminance - gray - signal
predominantly provides the resolution, which is the whole 6MP. If you could drop
out the luminance brightnesses from a digital image, the remaining color result
would look pretty bad.

Colin D.

Justin Thyme wrote:
"Toralf" wrote in message
...

Hi.

I'm still wondering about how good the image quality of modern digital
cameras (especially SLRs) really is, in particular how it compares with
35mm film. I've seen many articles on the subject on the Net, but few of
them seem to give you a lot of tangible information (I want to see the
numbers, please), and I can't help feeling that tests they refer to are
usually done to prove a point, i.e. that digital cameras are as good as
35mm, which is not the way you do proper research.

Check out http://clarkvision.com/imagedetail/f...digital.1.html
Seems to be not trying to prove a point. In some tests the film wins and in
some the digital wins.

To say a few words about myself, I'm working for a company that makes
high-accuracy, large-format scanners, so I'm not particularly impressed
when I hear e.g 6 million pixels (you need to talk about *billions* of
pixels if I'm really going to listen), and the word "interpolation"
leaves a bad taste in my mouth. But this also means I know that high
resolution isn't everything, of course; parameters like geometric
precision or signal-to-noise ratio also count a lot.

Actually, they mean SFA. I think too often we forget the purpose of
photography - to make images that look good. Who cares if the SN ratio is
crap if the image looks good. Some of my favorite digital photos are as
noisy as all heck, in these the noise added to the photo, not took away from
it.
So, essentially what you are saying is that the noise doesn't matter
anything, but it's somehow still contributing to the picture?


The proof isn't in the technical specifications, the proof is in
whether the photo looks good.
You're missing the point. The point of the technical specification is
actually that it tells you something about whether or not a photo will
generally look good - so you won't have to see a high number of them to
find out. Also, for most people a statistically significant number of
photos just won't be available, so all there is to go by is the numbers
and some highly subjective opinions. Of which I've found a lot of the
latter, while the former is obviously preferrable.

People will tell you that 2MP is no good
above 8x10 - I have a 16x12 photo made from 2MP on the wall that looks fine.
If you walk right up to it you can see some pixelation, but you can't see it
from a normal viewing distance of about 2 feet. Likewise I have images made
from ISO400 consumer grade film that look great too.

Be that as it may, some of the questions I'd like to have answered are
these:

1. What is the resolution of a 35mm film anyway? I think I read
somewhere that a colour negative is at least 3000dpi. Is that correct?
How about black&white? (Yeah I know, a film doesn't have pixels in
exactly the same sense as a digital image, but it *is* made up of
discrete elements after all.)

The site I posted above indicates that Fuji Velvia is approximately
equivalent to 15MP in it's resolving power.
OK. Thanks.

[ snip ]

Gordon Moat writes:

[an *extremely* detailed and clear discussion of many of the issues in
the topi in the subject line]

First, *very* nice explanation! It obviously involved quite a bit of
work.


Obviously you don't know Gordon's posts; he's capable of giving a *very* nice
explanation at a moment notice; no "quite a bit of work" required. .

Gordon Moat writes:

[an *extremely* detailed and clear discussion of many of the issues in
the topi in the subject line]

First, *very* nice explanation! It obviously involved quite a bit of
work.


Obviously you don't know Gordon's posts; he's capable of giving a *very* nice
explanation at a moment notice; no "quite a bit of work" required. .

Camera's with a decent quality lens (eg mid to
high end olympus, canon, nikon) don't suffer from purple fringing as bad as
the cheap cameras.

I really think Olympus makes the nicest high-end non-slr digital cameras; the
5060, the 8080 are digicams I'd love to buy.

The quality of construction, magnesium alloy bodies that are built like a tank
and superb glass, contrasts well with the cheap plastic bodies that canon
churns out and explains pretty well why Olympus is a loss making company while
Canon is a profitable business. You just get your money's worth when you buy
Olympus, they give it all away.

Camera's with a decent quality lens (eg mid to
high end olympus, canon, nikon) don't suffer from purple fringing as bad as
the cheap cameras.

I really think Olympus makes the nicest high-end non-slr digital cameras; the
5060, the 8080 are digicams I'd love to buy.

The quality of construction, magnesium alloy bodies that are built like a tank
and superb glass, contrasts well with the cheap plastic bodies that canon
churns out and explains pretty well why Olympus is a loss making company while
Canon is a profitable business. You just get your money's worth when you buy
Olympus, they give it all away.

"Michael Scarpitti" skrev i en meddelelse
om...
"MXP" wrote in message
...
All the tests I have seen where 35mm film is compared to a modern DSLR
(6-11MP)...the DSLR pictures shows more detail and less noise than a
fine
grained film like Provia 100F.

That's not so startling. That film is not as sharp as Kodachrome. It's
a poor choice to compare.

Kodachrome 25 was a nice film. But I don't have any. It was the only
Kodachrome.
I don't think Kodachrome 64 is sharper or more fine grain than any of the
100F's.
I want to see a prove of that.

It is quite fustrating that 6MP can beat
35mm.
I know many scanners can do 4000 dpi but if most of the information is
noise?

I still use film and it will be quite interresting to see a test where
e.g.
Provia 100F
shows more detail than an e.g. D1X/D70 or 1Ds/300D.

When I see my slides projected it seems strange that a 6MP DSLR can do
better....

Max


"Toralf" skrev i en meddelelse
...
Hi.

I'm still wondering about how good the image quality of modern digital
cameras (especially SLRs) really is, in particular how it compares
with
35mm film. I've seen many articles on the subject on the Net, but few
of
them seem to give you a lot of tangible information (I want to see the
numbers, please), and I can't help feeling that tests they refer to
are
usually done to prove a point, i.e. that digital cameras are as good
as
35mm, which is not the way you do proper research.

To say a few words about myself, I'm working for a company that makes
high-accuracy, large-format scanners, so I'm not particularly
impressed
when I hear e.g 6 million pixels (you need to talk about *billions* of
pixels if I'm really going to listen), and the word "interpolation"
leaves a bad taste in my mouth. But this also means I know that high
resolution isn't everything, of course; parameters like geometric
precision or signal-to-noise ratio also count a lot.

Be that as it may, some of the questions I'd like to have answered are
these:

1. What is the resolution of a 35mm film anyway? I think I read
somewhere that a colour negative is at least 3000dpi. Is that
correct?
How about black&white? (Yeah I know, a film doesn't have pixels in
exactly the same sense as a digital image, but it *is* made up of
discrete elements after all.)

2. What about the print? 300dpi?

3. I know that the most common sensors are made up of individual
elements for the read, green and blue channels, arranged in a special
pattern, whose data is somehow interpolated into RGB pixels. But what
exactly does e.g. 6 megapixels mean in that context? Does it mean that
the sensor has (just) 6 million elements, or that data from a higher
number (like 18 or 24 million) is combined into 6 million RGB pixels?

The same question more bluntly put: When Canon/Nikon/Pentax is talking
about 6MP, is that just a big a lie as the one about 10MP on Sigma
cameras? (I'm hoping not, as I think the Sigma/Foveon way of counting
really takes the cake.)

4. Can the inaccuracy associated with the above mentioned
interpolation
be quantified and/or measured against e.g. the error introduced by
scanning a negative with a film-scanner? And how does it compare with
pixel interpolation in the scanning sense?

5. And how about those other parameters I mentioned briefly above -
like
different kinds of geometric distortions, noise, flat field bias etc.?
Can those be compared with the ones of plain old film?

6. And the chromic aberration effects? How serious are they these
days?
And are the full-frame sensors that are actually found in some
high-end
cameras now, in any way comparable to film in that respect?

Well, maybe some people will say I have a somewhat critical or
conservative attitude towards digital cameras, but I actually think
you
ought to be a bit sceptical when something "new and wonderful" comes a
long; new technology is too often introduced for technology's own
sake,
IMO.

- Toralf

"Michael Scarpitti" skrev i en meddelelse
om...
"MXP" wrote in message
...
All the tests I have seen where 35mm film is compared to a modern DSLR
(6-11MP)...the DSLR pictures shows more detail and less noise than a
fine
grained film like Provia 100F.

That's not so startling. That film is not as sharp as Kodachrome. It's
a poor choice to compare.

Kodachrome 25 was a nice film. But I don't have any. It was the only
Kodachrome.
I don't think Kodachrome 64 is sharper or more fine grain than any of the
100F's.
I want to see a prove of that.

It is quite fustrating that 6MP can beat
35mm.
I know many scanners can do 4000 dpi but if most of the information is
noise?

I still use film and it will be quite interresting to see a test where
e.g.
Provia 100F
shows more detail than an e.g. D1X/D70 or 1Ds/300D.

When I see my slides projected it seems strange that a 6MP DSLR can do
better....

Max


"Toralf" skrev i en meddelelse
...
Hi.

I'm still wondering about how good the image quality of modern digital
cameras (especially SLRs) really is, in particular how it compares
with
35mm film. I've seen many articles on the subject on the Net, but few
of
them seem to give you a lot of tangible information (I want to see the
numbers, please), and I can't help feeling that tests they refer to
are
usually done to prove a point, i.e. that digital cameras are as good
as
35mm, which is not the way you do proper research.

To say a few words about myself, I'm working for a company that makes
high-accuracy, large-format scanners, so I'm not particularly
impressed
when I hear e.g 6 million pixels (you need to talk about *billions* of
pixels if I'm really going to listen), and the word "interpolation"
leaves a bad taste in my mouth. But this also means I know that high
resolution isn't everything, of course; parameters like geometric
precision or signal-to-noise ratio also count a lot.

Be that as it may, some of the questions I'd like to have answered are
these:

1. What is the resolution of a 35mm film anyway? I think I read
somewhere that a colour negative is at least 3000dpi. Is that
correct?
How about black&white? (Yeah I know, a film doesn't have pixels in
exactly the same sense as a digital image, but it *is* made up of
discrete elements after all.)

2. What about the print? 300dpi?

3. I know that the most common sensors are made up of individual
elements for the read, green and blue channels, arranged in a special
pattern, whose data is somehow interpolated into RGB pixels. But what
exactly does e.g. 6 megapixels mean in that context? Does it mean that
the sensor has (just) 6 million elements, or that data from a higher
number (like 18 or 24 million) is combined into 6 million RGB pixels?

The same question more bluntly put: When Canon/Nikon/Pentax is talking
about 6MP, is that just a big a lie as the one about 10MP on Sigma
cameras? (I'm hoping not, as I think the Sigma/Foveon way of counting
really takes the cake.)

4. Can the inaccuracy associated with the above mentioned
interpolation
be quantified and/or measured against e.g. the error introduced by
scanning a negative with a film-scanner? And how does it compare with
pixel interpolation in the scanning sense?

5. And how about those other parameters I mentioned briefly above -
like
different kinds of geometric distortions, noise, flat field bias etc.?
Can those be compared with the ones of plain old film?

6. And the chromic aberration effects? How serious are they these
days?
And are the full-frame sensors that are actually found in some
high-end
cameras now, in any way comparable to film in that respect?

Well, maybe some people will say I have a somewhat critical or
conservative attitude towards digital cameras, but I actually think
you
ought to be a bit sceptical when something "new and wonderful" comes a
long; new technology is too often introduced for technology's own
sake,
IMO.

- Toralf

"Toralf" wrote in message
...
Hi.

I'm still wondering about how good the image quality of modern digital
cameras (especially SLRs) really is, in particular how it compares with
35mm film. I've seen many articles on the subject on the Net, but few of
them seem to give you a lot of tangible information (I want to see the
numbers, please), and I can't help feeling that tests they refer to are
usually done to prove a point, i.e. that digital cameras are as good as
35mm, which is not the way you do proper research.

To say a few words about myself, I'm working for a company that makes
high-accuracy, large-format scanners, so I'm not particularly impressed
when I hear e.g 6 million pixels (you need to talk about *billions* of
pixels if I'm really going to listen), and the word "interpolation"
leaves a bad taste in my mouth. But this also means I know that high
resolution isn't everything, of course; parameters like geometric
precision or signal-to-noise ratio also count a lot.

Be that as it may, some of the questions I'd like to have answered are
these:

1. What is the resolution of a 35mm film anyway? I think I read
somewhere that a colour negative is at least 3000dpi. Is that correct?
How about black&white? (Yeah I know, a film doesn't have pixels in
exactly the same sense as a digital image, but it *is* made up of
discrete elements after all.)

When Kodak brought out their 13 Mp camera, they said it equals thr
reoslution of 35 mm film. Halation in the emulsion limits the resolution of
film.


2. What about the print? 300dpi?

Unless you have exceptional paper, somewhere around 250 dpi gives the
maximum resolution. The limitation here is the spreading of the ink
droplets.


3. I know that the most common sensors are made up of individual
elements for the read, green and blue channels, arranged in a special
pattern, whose data is somehow interpolated into RGB pixels. But what
exactly does e.g. 6 megapixels mean in that context? Does it mean that
the sensor has (just) 6 million elements, or that data from a higher
number (like 18 or 24 million) is combined into 6 million RGB pixels?

That color data from 6 Mp is converted to 6 Mp. The math is tricky, and
there are many misunderstandings. To convince oyurself, it would be best to
take photos of a resolution test chart.


The same question more bluntly put: When Canon/Nikon/Pentax is talking
about 6MP, is that just a big a lie as the one about 10MP on Sigma
cameras? (I'm hoping not, as I think the Sigma/Foveon way of counting
really takes the cake.)

Hard data on this is hard to come by. I haven't seen any - just arm-waving
arguments.


4. Can the inaccuracy associated with the above mentioned interpolation
be quantified and/or measured against e.g. the error introduced by
scanning a negative with a film-scanner? And how does it compare with
pixel interpolation in the scanning sense?

Again, hard date will trump theory. But the comparisons must be done
carefully to avoid unintended artifacts.

5. And how about those other parameters I mentioned briefly above - like
different kinds of geometric distortions, noise, flat field bias etc.?
Can those be compared with the ones of plain old film?

I think they are better than film. Film is subject to distortion in the
camera and in processing. Anyway, software can correct mst distortions.


6. And the chromic aberration effects? How serious are they these days?
And are the full-frame sensors that are actually found in some high-end
cameras now, in any way comparable to film in that respect?

It seems ot depend on the particular camera. When I had an Olympus 3040, I
saw many complaints about "purple fringing", often misidentified as
chromatic aberration - which is a lens problem. I looked for the fringing
in some of my photos with sharp, high-contrast edges, where the effect is
supposed ot be present. It wasn't there.


Well, maybe some people will say I have a somewhat critical or
conservative attitude towards digital cameras, but I actually think you
ought to be a bit sceptical when something "new and wonderful" comes a
long; new technology is too often introduced for technology's own sake,
IMO.

Digital imaging isn't new anymore. It is routinely used in some of the most
demanding photographic applications, like astronomy.


- Toralf

"Toralf Lund" wrote in message
...
Stephen H. Westin wrote:
Toralf writes:
[ snip ]



Be that as it may, some of the questions I'd like to have answered are
these:

1. What is the resolution of a 35mm film anyway?


It's hard to say, as the resolution limit is different from that of a
digital sensor. Rather than a hard limit, you get less information and
more blur and noise as you increase resolution in scanning a piece of
film.


I think I read
somewhere that a colour negative is at least 3000dpi. Is that
correct?


It's in the ballpark. [ ... ]
OK. Thanks

That means a 24 x 36 mm sensing plane would need about 12 megapixels to have
the same resolution as film. Digital cameras are not too far from that
now....Perhaps in another couple of years..........