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Need help in calculating digital camera's MP



 
 
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  #21  
Old January 9th 09, 10:33 AM posted to rec.photo.digital,uk.rec.photo.misc
Trev
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Posts: 81
Default Need help in calculating digital camera's MP

In ,
John Navas bashed on keyboard and typed:
On Thu, 8 Jan 2009 13:27:55 -0800 (PST), Scott W
wrote in
:

On Jan 8, 10:12 am, John Navas wrote:
On Wed, 07 Jan 2009 00:33:34 GMT, TheRealSteve
wrote in :


I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

21MP on a FF 35mm camera is not all that high, any decent lens should
be able to make full use of the pixels. ...


Actually at the limit of the resolving power of Canon zoom lenses
under ideal conditions.


The resolving power of the lens is far greater than the resolving power of
the sensor and there is no connection between the two other then one focus
the light to fall on the other

--
Trev
Nobody is perfect.
But Being a Yorkshire man is as close as you can get.


  #22  
Old January 9th 09, 10:34 PM posted to rec.photo.digital,uk.rec.photo.misc
John Navas[_2_]
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Posts: 3,956
Default Need help in calculating digital camera's MP

On Fri, 9 Jan 2009 09:29:44 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and typed:
On Thu, 8 Jan 2009 21:22:43 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and
typed:


Yes I reckon with a decent lens you can still get good detail at
60" x 40".

Not in 35 mm.

Why not? If you use something like a 35mm 21MP 1DsMkIII and print
to 60x40", you're getting over 90 ppi. While not great, if viewed
from more than a foot or two away, you'd wouldn't be able to make
out pixelation if the printer is doing any interpolation. But once
again, pixel level noise, CA, etc, would be very important.

I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

As I remember it, the lens resolving power was mesured in Lines per
Millmeter. Typical for a lens made to fit a 35 mm body is 40 to 60
lpm


Now do the math on the size of the sensor.


What has the sensor got to do with it? As long as a lens can resolve more
then the media used to capture its output you will get the best you can.


The size of the sensor is the area of the captured image, and the
resolving power of the lens in terms of pixels is one of the two
limiting factors on captured resolution, the other being the resolution
of the sensor, with the captured resolution being roughly the lower of
the two.

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others
  #23  
Old January 9th 09, 10:34 PM posted to rec.photo.digital,uk.rec.photo.misc
John Navas[_2_]
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Posts: 3,956
Default Need help in calculating digital camera's MP

On Fri, 9 Jan 2009 09:33:24 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and typed:
On Thu, 8 Jan 2009 13:27:55 -0800 (PST), Scott W
wrote in
:

On Jan 8, 10:12 am, John Navas wrote:
On Wed, 07 Jan 2009 00:33:34 GMT, TheRealSteve
wrote in :


I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

21MP on a FF 35mm camera is not all that high, any decent lens should
be able to make full use of the pixels. ...


Actually at the limit of the resolving power of Canon zoom lenses
under ideal conditions.


The resolving power of the lens is far greater than the resolving power of
the sensor and there is no connection between the two other then one focus
the light to fall on the other


Not true.

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others
  #24  
Old January 10th 09, 01:06 AM posted to rec.photo.digital,uk.rec.photo.misc
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Need help in calculating digital camera's MP

On Fri, 9 Jan 2009 09:33:24 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and typed:
On Thu, 8 Jan 2009 13:27:55 -0800 (PST), Scott W
wrote in
:

On Jan 8, 10:12 am, John Navas wrote:
On Wed, 07 Jan 2009 00:33:34 GMT, TheRealSteve
wrote in :


I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

21MP on a FF 35mm camera is not all that high, any decent lens should
be able to make full use of the pixels. ...


Actually at the limit of the resolving power of Canon zoom lenses
under ideal conditions.


The resolving power of the lens is far greater than the resolving power of
the sensor and there is no connection between the two other then one focus
the light to fall on the other


Not so.

Simplified math:

The Canon sensor has a resolution of 5,616 x 3,744 pixels
on a sensor size of 36 x 24 mm.
That's 156 pixels/mm, which needs minimum resolving power of 78 li/mm.
There are very few lenses with that kind of resolving power.
Good zoom lenses are on the order of 40 li/mm.
More resolving power (contrast) is needed for pixel-level crispness.

More complete math:

http://www.luminous-landscape.com/tutorials/resolution.shtml

Consider a 35mm system with a lens at f/11. At best, the maximum
resolution you will get is equivalent to 16 MP, even if your camera
has 22 or 25 MP. In the case of an APS-C based system the limit goes
to 7 MP, and 4 MP considering a Four Thirds format. Stopping down to
f/22 the limit of the effective resolution of the 35mm based system
goes to 4 MP!

Only for highly corrected lenses (with better performance at f/5.6
than f/8) do higher sensor resolutions make sense. For instance, you
can put 60 million of pixels into a 35mm sensor, but only a
diffraction-limited lens at f/5.6 would take advantage of it.

Sensors for larger formats are approaching the diffraction limit of
real lenses, and it is more difficult to get high levels of
aberration suppression for them. THE POINT IS THAT YOU CANNOT FULLY
EXPLOIT THE RESOLUTION POTENTIAL OF HIGH-RESOLUTION SENSORS WITH
REGULAR MASS-PRODUCED LENSES, PARTICULARLY FOR LARGER FORMATS.
[emphasis added]

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others
  #25  
Old January 10th 09, 02:27 AM posted to rec.photo.digital,uk.rec.photo.misc
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Need help in calculating digital camera's MP

On Fri, 9 Jan 2009 17:08:51 -0800 (PST), Scott W
wrote in
:

On Jan 9, 2:06*pm, John Navas wrote:


Simplified math:

The Canon sensor has a resolution of 5,616 x 3,744 pixels
on a sensor size of 36 x 24 mm.
That's 156 pixels/mm, which needs minimum resolving power of 78 li/mm.
There are very few lenses with that kind of resolving power.
Good zoom lenses are on the order of 40 li/mm.
More resolving power (contrast) is needed for pixel-level crispness.

More complete math:

http://www.luminous-landscape.com/tutorials/resolution.shtml

* *Consider a 35mm system with a lens at f/11. At best, the maximum
* *resolution you will get is equivalent to 16 MP, even if your camera
* *has 22 or 25 MP. In the case of an APS-C based system the limit goes
* *to 7 MP, and 4 MP considering a Four Thirds format. Stopping down to
* *f/22 the limit of the effective resolution of the 35mm based system
* *goes to 4 MP!

* *Only for highly corrected lenses (with better performance at f/5.6
* *than f/8) do higher sensor resolutions make sense. For instance, you
* *can put 60 million of pixels into a 35mm sensor, but only a
* *diffraction-limited lens at f/5.6 would take advantage of it.

* *Sensors for larger formats are approaching the diffraction limit of
* *real lenses, and it is more difficult to get high levels of
* *aberration suppression for them. THE POINT IS THAT YOU CANNOT FULLY
* *EXPLOIT THE RESOLUTION POTENTIAL OF HIGH-RESOLUTION SENSORS WITH
* *REGULAR MASS-PRODUCED LENSES, PARTICULARLY FOR LARGER FORMATS.
* *[emphasis added]


So use a better lens, not everyone uses zooms exclusively.


"Then let them eat cake!"

Only a very few premium lenses, carefully used at medium aperture, are
able to match that sensor.

I know that I get more scene detail when I put a 1.4x tele-converter
in front of my 300mm f/4 lens, compared to just using the 300mm lens.


Samples please.

If the lens was not resolving more then the sensor could pickup then
there would be no added detail, there would be more pixels / degree
but all detail that could be seen with the 1.4 converter would also be
visible without the converter.


What sensor?

If you look back into the camera what the converter is doing is making
the pixel density higher, from around 6.5 microns pitch to around 4.6.

With both my 50mm and 300mm lens I often get aliasing, something that
I would not see if the sensor had more pixels then needed, in fact it
tell me for those lenses I could use more pixels/mm.


What are the resolving powers of those two lenses in lp/mm at your
working aperture? (You can roughly determine the values from the MTF
curves.)

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others
  #26  
Old January 10th 09, 08:37 AM posted to rec.photo.digital
David J Taylor[_9_]
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Posts: 262
Default Need help in calculating digital camera's MP

Scott W wrote:
[]
With both my 50mm and 300mm lens I often get aliasing, something that
I would not see if the sensor had more pixels then needed, in fact it
tell me for those lenses I could use more pixels/mm.

Scott


... and you would not see aliasing anything like as often if you camera had
a properly designed anti-aliasing filter. The high spatial frequency
components from the image should not be allowed to reach the sensor.

David

  #27  
Old January 10th 09, 11:07 AM posted to rec.photo.digital,uk.rec.photo.misc
Trev
external usenet poster
 
Posts: 81
Default Need help in calculating digital camera's MP

In ,
John Navas bashed on keyboard and typed:
On Fri, 9 Jan 2009 09:33:24 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and
typed:
On Thu, 8 Jan 2009 13:27:55 -0800 (PST), Scott W
wrote in
:

On Jan 8, 10:12 am, John Navas wrote:
On Wed, 07 Jan 2009 00:33:34 GMT, TheRealSteve
wrote in :

I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

21MP on a FF 35mm camera is not all that high, any decent lens
should be able to make full use of the pixels. ...

Actually at the limit of the resolving power of Canon zoom lenses
under ideal conditions.


The resolving power of the lens is far greater than the resolving
power of the sensor and there is no connection between the two other
then one focus the light to fall on the other


Not so.

Simplified math:

The Canon sensor has a resolution of 5,616 x 3,744 pixels
on a sensor size of 36 x 24 mm.
That's 156 pixels/mm, which needs minimum resolving power of 78 li/mm.
There are very few lenses with that kind of resolving power.
Good zoom lenses are on the order of 40 li/mm.
More resolving power (contrast) is needed for pixel-level crispness.


Ah but the lens can resolve the 40 lpm ( x2 = 80 a sq millimeter) on to one
sq pixel


More complete math:

http://www.luminous-landscape.com/tutorials/resolution.shtml

Consider a 35mm system with a lens at f/11. At best, the maximum
resolution you will get is equivalent to 16 MP, even if your camera
has 22 or 25 MP. In the case of an APS-C based system the limit goes
to 7 MP, and 4 MP considering a Four Thirds format. Stopping down to
f/22 the limit of the effective resolution of the 35mm based system
goes to 4 MP!

Only for highly corrected lenses (with better performance at f/5.6
than f/8) do higher sensor resolutions make sense. For instance, you
can put 60 million of pixels into a 35mm sensor, but only a
diffraction-limited lens at f/5.6 would take advantage of it.

Sensors for larger formats are approaching the diffraction limit of
real lenses, and it is more difficult to get high levels of
aberration suppression for them. THE POINT IS THAT YOU CANNOT FULLY
EXPLOIT THE RESOLUTION POTENTIAL OF HIGH-RESOLUTION SENSORS WITH
REGULAR MASS-PRODUCED LENSES, PARTICULARLY FOR LARGER FORMATS.
[emphasis added]




--
Trev
Nobody is perfect.
But Being a Yorkshire man is as close as you can get.


  #28  
Old January 10th 09, 09:07 PM posted to rec.photo.digital,uk.rec.photo.misc
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Need help in calculating digital camera's MP

On Sat, 10 Jan 2009 10:07:18 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and typed:


Simplified math:

The Canon sensor has a resolution of 5,616 x 3,744 pixels
on a sensor size of 36 x 24 mm.
That's 156 pixels/mm, which needs minimum resolving power of 78 li/mm.
There are very few lenses with that kind of resolving power.
Good zoom lenses are on the order of 40 li/mm.
More resolving power (contrast) is needed for pixel-level crispness.


Ah but the lens can resolve the 40 lpm ( x2 = 80 a sq millimeter) on to one
sq pixel


Nope. Doesn't work that way.
Read the citation from my post that you snipped:
http://www.luminous-landscape.com/tutorials/resolution.shtml

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others
  #29  
Old January 10th 09, 11:37 PM posted to rec.photo.digital,uk.rec.photo.misc
Roger Blackwell
external usenet poster
 
Posts: 7
Default Need help in calculating digital camera's MP

"John Navas" wrote in message
...
On Fri, 9 Jan 2009 09:33:24 -0000, "Trev" trevbowdenAT.dsl.pipex.COM
wrote in :

In ,
John Navas bashed on keyboard and typed:
On Thu, 8 Jan 2009 13:27:55 -0800 (PST), Scott W
wrote in
:

On Jan 8, 10:12 am, John Navas wrote:
On Wed, 07 Jan 2009 00:33:34 GMT, TheRealSteve
wrote in :

I'm talking resolving power of the lens, not just the number of
megapixels in the sensor.

21MP on a FF 35mm camera is not all that high, any decent lens should
be able to make full use of the pixels. ...

Actually at the limit of the resolving power of Canon zoom lenses
under ideal conditions.


The resolving power of the lens is far greater than the resolving power of
the sensor and there is no connection between the two other then one focus
the light to fall on the other


Not so.

Simplified math:

The Canon sensor has a resolution of 5,616 x 3,744 pixels
on a sensor size of 36 x 24 mm.
That's 156 pixels/mm, which needs minimum resolving power of 78 li/mm.
There are very few lenses with that kind of resolving power.
Good zoom lenses are on the order of 40 li/mm.
More resolving power (contrast) is needed for pixel-level crispness.

More complete math:

http://www.luminous-landscape.com/tutorials/resolution.shtml

Consider a 35mm system with a lens at f/11. At best, the maximum
resolution you will get is equivalent to 16 MP, even if your camera
has 22 or 25 MP. In the case of an APS-C based system the limit goes
to 7 MP, and 4 MP considering a Four Thirds format. Stopping down to
f/22 the limit of the effective resolution of the 35mm based system
goes to 4 MP!

Only for highly corrected lenses (with better performance at f/5.6
than f/8) do higher sensor resolutions make sense. For instance, you
can put 60 million of pixels into a 35mm sensor, but only a
diffraction-limited lens at f/5.6 would take advantage of it.

Sensors for larger formats are approaching the diffraction limit of
real lenses, and it is more difficult to get high levels of
aberration suppression for them. THE POINT IS THAT YOU CANNOT FULLY
EXPLOIT THE RESOLUTION POTENTIAL OF HIGH-RESOLUTION SENSORS WITH
REGULAR MASS-PRODUCED LENSES, PARTICULARLY FOR LARGER FORMATS.
[emphasis added]


Well, having said all that a 60" x 40" print from a dSLR will still be
acceptable (at least to my personal standards) if it is interpolated to 300
dpi and the sharpness is the best that can be obtained. After all, who goes
to art galleries with a magnifying glass looking to see the most detail in
the paintwork?

Roger


  #30  
Old January 11th 09, 09:01 AM posted to rec.photo.digital
David J Taylor[_9_]
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Posts: 262
Default Need help in calculating digital camera's MP

Roger Blackwell wrote:
[]
Well, having said all that a 60" x 40" print from a dSLR will still be
acceptable (at least to my personal standards) if it is interpolated
to 300 dpi and the sharpness is the best that can be obtained. After
all, who goes to art galleries with a magnifying glass looking to see
the most detail in the paintwork?

Roger


... and would probably look just as stunning if it were from a 5MP camera
if the subject is interesting enough to justify such a print.

David

 




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