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



 
 
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  #1  
Old July 22nd 04, 09:00 PM
Toralf
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Default Digital quality (vs 35mm): Any real answers?

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
  #2  
Old July 22nd 04, 09:45 PM
Dave Herzstein
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

Toralf wrote:
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.
.....


Why not convince yourself (one way or the other) by comparing
side-by-side prints (or whatever final output you like) of 35mm
prints/scans and 6MP DSLR. I viewed some 20" X 30" prints from a 6PM
digital, bought one, sold my film bodies and haven't regreted it. YMMV

-Dave
  #3  
Old July 22nd 04, 10:35 PM
nitzsche
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.

2. What about the print? 300dpi

- Unless you're printing posters, it's not relevant.

3. exactly does e.g. 6 megapixels mean

- 6.3 megapixels is 6,291,456 sensors.

4. Can the inaccuracy associated with the above mentioned

interpolation be measured
- Film will almost always be better, but it's what the outside eyes see
that matters.

5. geometric distortions, noise, flat field bias etc.

- That's a lens issues, not sensor/film issues

6. And the chromic aberration effects?

- As far as I know, all digicams are prone to purple fringing, which is
something you don't see on any cheap slr.

My two cents worth.


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

  #4  
Old July 22nd 04, 11:01 PM
Stephen H. Westin
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

nitzsche writes:

OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.


Not in this universe. For practical purposes, it's somewhere between
30-75 cycles/mm, most of the time.

snip

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.
  #5  
Old July 23rd 04, 08:10 AM
Toralf Lund
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

nitzsche wrote:
OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.

2. What about the print? 300dpi

- Unless you're printing posters, it's not relevant.

But I want to *know* exactly how large prints you can make at "standard"
resolution with the different formats.


3. exactly does e.g. 6 megapixels mean

- 6.3 megapixels is 6,291,456 sensors.

So, it's *really* equivalent to about 2M of true RGB data???

4. Can the inaccuracy associated with the above mentioned

interpolation be measured
- Film will almost always be better, but it's what the outside eyes see
that matters.

5. geometric distortions, noise, flat field bias etc.

- That's a lens issues, not sensor/film issues

There are lens issues, but those are not the ones I'm talking about.
CCDs at least do have the problem that the light sensitivity of each
pixel or sensor is not quite the same. And there may be varying offsets,
too, i.e. each pixel doesn't quite have the same opinion on what "black"
is. Also, the individual sensors aren't necessarily evenly distributed
or positioned exactly right. Then there is the "smear" between adjacent
pixels, which is one of the arguments against CCD and for CMOS, I think.


6. And the chromic aberration effects?

- As far as I know, all digicams are prone to purple fringing, which is
something you don't see on any cheap slr.

My two cents worth.



  #6  
Old July 24th 04, 09:51 PM
Sander Vesik
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

In rec.photo.equipment.35mm Toralf Lund wrote:
nitzsche wrote:
OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.

2. What about the print? 300dpi

- Unless you're printing posters, it's not relevant.

But I want to *know* exactly how large prints you can make at "standard"
resolution with the different formats.


This mainly depends on teh subject you are photographing, and the resolution
you want varies between 600+ PPI to 150PPI.


--
Sander

+++ Out of cheese error +++
  #7  
Old July 24th 04, 09:51 PM
Sander Vesik
external usenet poster
 
Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

In rec.photo.equipment.35mm Toralf Lund wrote:
nitzsche wrote:
OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.

2. What about the print? 300dpi

- Unless you're printing posters, it's not relevant.

But I want to *know* exactly how large prints you can make at "standard"
resolution with the different formats.


This mainly depends on teh subject you are photographing, and the resolution
you want varies between 600+ PPI to 150PPI.


--
Sander

+++ Out of cheese error +++
  #8  
Old July 23rd 04, 11:49 AM
Justin Thyme
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?


"nitzsche" wrote in message
. ..
6. And the chromic aberration effects?

- As far as I know, all digicams are prone to purple fringing, which is
something you don't see on any cheap slr.

You don't see it on all digicams - it is directly proportional to the
quality of the lens on the digicam.

Here in Australia a cheap film SLR is about $400-$500, with a 28-80 lens. Of
that, about $250 is the lens and the remainder is the body. Considering
that a compact digital with a similar zoom range can be picked up for $300 -
6x zoom for $400 and 10x for $500, it is pretty clear to see the difference
in quality of lens used. 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 dunno what the prices in the USA would be, but I
suspect the ratio of the prices would be pretty similar


  #9  
Old July 24th 04, 09:48 PM
Sander Vesik
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

In rec.photo.equipment.35mm nitzsche wrote:
OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.


While a popular answer, its also untrue. I don't think anybody will get
more the 100mp from 35mm sensor in the next 100 years.

--
Sander

+++ Out of cheese error +++
  #10  
Old July 22nd 04, 11:01 PM
Stephen H. Westin
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Posts: n/a
Default Digital quality (vs 35mm): Any real answers?

nitzsche writes:

OK, I'll take a shot at it...

It used to be "Film is cheap,' now it's "Cameras are cheap."

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

- For practical purposes, it's infinite.


Not in this universe. For practical purposes, it's somewhere between
30-75 cycles/mm, most of the time.

snip

--
-Stephen H. Westin
Any information or opinions in this message are mine: they do not
represent the position of Cornell University or any of its sponsors.
 




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