A Photography forum. PhotoBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » PhotoBanter.com forum » Digital Photography » Digital SLR Cameras
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Math question - sort of



 
 
Thread Tools Display Modes
  #21  
Old September 26th 09, 02:40 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Eric Miller[_3_]
external usenet poster
 
Posts: 11
Default Math question - sort of

Kennedy McEwen wrote:
In article , Eric Miller
writes
Kennedy McEwen wrote:

If it is just about the math then you need to quantify the lens
quality contribution as well


No, the question posed in the original post had nothing to do with that.

I suggest you read what you wrote in your question again and, in future
ask what you mean or mean what you ask! You specifically refer to
resolution and that is a lot more than just pixel density!

- your math is less than half the story, dealing only with pixel
geometry.


That would actually be the whole story, since the original question
strictly concerned the pixels.

No, you stated: "if there is a way to think of resolution as effective
focal length versus the 10D".


Which is a selective quote designed to explain your need to pontificate
about something other than what was really asked (and as argument that
the most direct and succinct response to the question posed really
missed the point), which was:

"So, for example, if I were to get a 7D at 18 megapixels how would that
compare to 10D resolution wise in terms of what focal length lens would
I have had to put on the 10D to get a 5 inch tall bird at 20 meters (or
any distance) to be rendered by the same number of pixels (one dimension
only or my head will hurt too much) on the 10D that it would be rendered
on the 7D using the 400mm lens."

It isn't surprising that, on the usenet, posters will feel the necessity
to take every question as an opportunity to educate those lesser minds
about what they really should have asked. But why hide from that conceit
by quoting a selected part of the preamble to my math question to
suggest that I really asked about that which you want to talk about?
Seriously, why not just say what your thinking? You're smarter than
everyone else and we should all worship you, right?

Oh wait, let me mimic that little voice you just heard, "Remember, this
post is an opportunity to tell them more of what we know about what they
should have been asking, but were too ignorant to, hee hee hee . . . God
we are smart."

Eric Miller
www.dyesscreek.com
  #22  
Old September 26th 09, 03:50 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Kennedy McEwen
external usenet poster
 
Posts: 639
Default Math question - sort of

In article , Eric Miller
writes
Kennedy McEwen wrote:
In article , Eric Miller
writes
Kennedy McEwen wrote:

If it is just about the math then you need to quantify the lens
quality contribution as well

No, the question posed in the original post had nothing to do with that.

I suggest you read what you wrote in your question again and, in
future ask what you mean or mean what you ask! You specifically
refer to resolution and that is a lot more than just pixel density!

- your math is less than half the story, dealing only with pixel
geometry.

That would actually be the whole story, since the original question
strictly concerned the pixels.

No, you stated: "if there is a way to think of resolution as
effective focal length versus the 10D".


Which is a selective quote designed to explain your need to pontificate
about something other than what was really asked


No it is an exact quote of your question, excluding the waffle that put
it in context as that was already clear from the preceding thread.

"So, for example, if I were to get a 7D at 18 megapixels how would that
compare to 10D resolution wise in terms of what focal length lens would
I have had to put on the 10D to get a 5 inch tall bird at 20 meters (or
any distance) to be rendered by the same number of pixels (one
dimension only or my head will hurt too much) on the 10D that it would
be rendered on the 7D using the 400mm lens."

Context. The answer is NOT simply scaling pixel size of the 10D to the
7D, which is what you were given. Without taking optical resolution
into account the equivalent focal length you would need on the 10D
compared to the 7D could be close to 50% higher than is in fact the
case! Optics, even perfect optics, don't have infinite resolution! When
the optical resolution is close to the pixel resolution then they MUST
be taken into account to answer your question, or you end up with
meaningless unresolved pixels. You seem to have a major problem
understanding that.

It isn't surprising that, on the usenet, posters will feel the
necessity to take every question as an opportunity to educate those
lesser minds about what they really should have asked.


When you were 5 and asked your Mom where you came from, you were
probably happy with her reply that a stork brought you. By the time you
were 10 you would expect a better, more complete answer, to exactly the
same question. By the time you were 15 you ought to know the full
answer yourself. Stop behaving like a 5 year old - there is no Santa
Claus, even if some of your friends still believe there is!

Oh wait, let me mimic that little voice you just heard, "Remember, this
post is an opportunity to tell them more of what we know about what
they should have been asking, but were too ignorant to, hee hee hee . .
. God we are smart."

Smart enough to know that any question I ask may well have an answer
which is more complex than I expected and with enough common decency not
to criticise those who make the effort to explain that.

Carry on living in ignorance: the x1.7 scale factor given by the partial
answer is at least 50% too high. A 400mm lens on the 7D would NOT give
equivalent resolution to a 680mm lens on a 10D: you will be lucky to
achieve half of that 280mm effective focal length extension depending on
the optical resolution of the 400mm lens in question. In other words
540mm, or less, equivalence in terms of what is actually RESOLVED.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's ****ed.
Python Philosophers (replace 'nospam' with 'kennedym' when replying)
  #23  
Old September 27th 09, 03:41 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
John Sheehy
external usenet poster
 
Posts: 878
Default Math question - sort of

John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml


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.


The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.
  #24  
Old September 27th 09, 03:55 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Alan Browne
external usenet poster
 
Posts: 12,640
Default Math question - sort of

John Sheehy wrote:
John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml


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.


The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.


Is that another way of saying the Kodak empirical formula for end image
resolution (on film) is...

1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ?

So increasing either the sensor density or the lens resolution results
in higher output resolution, though of course with diminishing returns.
  #25  
Old September 27th 09, 04:46 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Paul Furman
external usenet poster
 
Posts: 7,367
Default Math question - sort of

John Sheehy wrote:

The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems.


Extreme microlenses can emphasize CA and even vignetting. I don't know
if that's necessarily proportional to pixel density but it appears to be
more of an issue.

Lower densities lower the resolution, so you see less of everything,
including subject detail.


--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
  #26  
Old September 27th 09, 05:25 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Paul Furman
external usenet poster
 
Posts: 7,367
Default Math question - sort of

Paul Furman wrote:
Eric Miller wrote:
I went from the 10D to the 5D. When I had my 10D, I learned to like
the 1.6x way of fooling myself into thinking my 400mm lens was a 560mm
lens. Now I am thinking of getting myself another birding camera and
am trying to figure out if there is a way to think of resolution as
effective focal length versus the 10D. So, for example, if I were to
get a 7D at 18 megapixels how would that compare to 10D resolution
wise in terms of what focal length lens would I have had to put on the
10D to get a 5 inch tall bird at 20 meters (or any distance) to be
rendered by the same number of pixels (one dimension only or my head
will hurt too much) on the 10D that it would be rendered on the 7D
using the 400mm lens.


It's all relative,...
...but yes it would be useful to have a common terminology for
describing pixel magnification rather than 35mm equivalent FOV. Hmm, I
was thinking macro when I wrote "pixel magnification" but at infinity I
guess it would be pixels/field of view in degrees?


On second thought, the original question is about magnification, just
magnification at/near infinity. FOV only matters here if the 5 inch tall
bird goes outside the frame. Print size doesn't exactly matter either
unless you want the result in inches instead of pixels, the only
question is how much the bird can be enlarged.

Set the number relative to a 'normal' lens, which coincidentally is very
close to 50 degrees for the diagonal FOV of a 50mm lens on a 35mm
camera. Then let's use 300dpi as a standard metric for enlargement, on
an 8x10 print that's 2400x3000 or 7.2MP. So, a full frame 7.2MP camera
making an acceptable 8x10 print with a normal lens of 50 degrees
diagonal field of view represents the basepoint.


This is still a handy basepoint. How many pixels tall would the 5 inch
bird be for a 7.2MP full frame 35mm camera, focused to infinity? I guess
we need to know how far away the bird is.

Damn, now I've exceeded my mathematical skills and/or patience...

...It would look something like if
you doubled the focal length, the number would be 2 and the number is 1
with the default setup.


Or if you double the linear pixel count, that doubles the number also.
So the pixel spacing is really all you need, though it's nice to nail it
all back to that normal lens at infinity and an 8x10 print as the basepoint.


A 500mm lens on FX would be a 10 and a 10mm FX
fisheye would be -5.


Yeah, this is magnification, like binoculars, microscopes & telescopes
are described as 5x, 10x, etc.

scratch this comment:

I'm not certain what doubling the megapixel count
would do to the number, probably not double it.

Can anyone finish my logic? A chart would be nice g.


Lastly, the lens has resolution limits so you can say that the lens is
only good up to a particular magnification and decide not to waste money
on pixels beyond that point. However, the point where a lens gives up is
variable according to many factors like how close to the edge or center,
what aperture, subject distance/magnification, etc. The MTF charts have
to pick a narrow definition and the nyquist lines on those have to pick
a simple theoretical diffraction point but there is usually some
discernible detail beyond that even if it doesn't meet the strict criteria.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
  #27  
Old September 27th 09, 09:49 PM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
You Are The Weakest Link
external usenet poster
 
Posts: 2
Default Math question - sort of

On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne
wrote:

John Sheehy wrote:
John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml


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.


The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.


Is that another way of saying the Kodak empirical formula for end image
resolution (on film) is...

1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ?

So increasing either the sensor density or the lens resolution results
in higher output resolution, though of course with diminishing returns.


Film has silver grain (analog photosites) sizes of 2um or less, the size of
photosites on most small sensor cameras of 1/2.5 being approx. 2um. You
will always be limited to your weakest link. If you increase the lens
resolution you are limited to the resolution of your sensor being 4-8um in
photosite sizes. (Luckily, in P&S cameras the optics quality and resolution
is matched to the photosite sizes.) If you increase the pixel density
without increasing the lens quality then all you are capturing with those
smaller photosites are the blurry edges afforded by the lens. No gain in
useful information. A bit like those toy telescopes that advertise 600x
magnification on a 2" diameter objective lens. All you are doing is
magnifying blur beyond 50x magnification with a 2" lens. Or those that put
high-gain amplifiers on their fringe-area TV antennas to only amply noise.

It's not an "either/or" venture. It's an "and" issue.
  #28  
Old September 28th 09, 01:27 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
John Sheehy
external usenet poster
 
Posts: 878
Default Math question - sort of

Paul Furman wrote in
:

John Sheehy wrote:

The lenses are to blame for any optical issues with high densities.
The higher density *NEVER* exacerbates any lens problems.


Extreme microlenses can emphasize CA and even vignetting. I don't know
if that's necessarily proportional to pixel density but it appears to
be more of an issue.

Lower densities lower the resolution, so you see less of everything,
including subject detail.


I meant the density itself. Of course, microlenses could be poorly
designed. Even then, however, oversampling allows extemely easy and smooth
correction of CA, both from the lens, and that generated by poor
microlenses.
  #29  
Old September 28th 09, 02:02 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
Alan Browne
external usenet poster
 
Posts: 12,640
Default Math question - sort of

You Are The Weakest Link wrote:
On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne
wrote:

John Sheehy wrote:
John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml

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.
The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.

Is that another way of saying the Kodak empirical formula for end image
resolution (on film) is...

1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ?

So increasing either the sensor density or the lens resolution results
in higher output resolution, though of course with diminishing returns.


It's not an "either/or" venture. It's an "and" issue.


You really don't know how to read and understand that "increasing
either" also includes "increasing both" do you?
  #30  
Old September 28th 09, 03:34 AM posted to rec.photo.equipment.35mm,rec.photo.digital,rec.photo.digital.slr-systems
You Are The Weakest Link
external usenet poster
 
Posts: 2
Default Math question - sort of

On Sun, 27 Sep 2009 21:02:51 -0400, Alan Browne
wrote:

You Are The Weakest Link wrote:
On Sun, 27 Sep 2009 10:55:01 -0400, Alan Browne
wrote:

John Sheehy wrote:
John Navas wrote in
:

On Fri, 25 Sep 2009 17:10:27 -0400, "Charles"
wrote in
:

Let the reader decide:

http://www.luminous-landscape.com/tu...solution.shtml

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.
The lenses are to blame for any optical issues with high densities. The
higher density *NEVER* exacerbates any lens problems. Lower densities
lower the resolution, so you see less of everything, including subject
detail.

You position is all "talk" and "logic". You can not demonstrate what you
believe, because it only exists in bad logic and bad paradigms.

Here's what happens when you try to demonstrate, and go about it the
right way:

You shoot the same scene with the same lens, same ISO, same Av and Tv,
and then you use a converter with no noise reduction, and upsample
critical crops from both images to the same subject size. No matter how
much lens fault is brought into the light with the higher density, the
higher density still has a more accurate rendition of the subject,
because those faults ARE ALWAYS THERE, REGARDLESS OF PIXEL DENSITY. Less
agressive sampling does not avoid lens issues; it just makes it harder to
tell why the image has so much less real subject detail.
Is that another way of saying the Kodak empirical formula for end image
resolution (on film) is...

1/sqrt(res_out) = 1/sqrt(res_lens) + 1/sqrt(res_sensor) ?

So increasing either the sensor density or the lens resolution results
in higher output resolution, though of course with diminishing returns.


It's not an "either/or" venture. It's an "and" issue.


You really don't know how to read and understand that "increasing
either" also includes "increasing both" do you?


You don't know how to comprehend that increasing either does NOT include
increasing both.

Pray tell, if you have a sensor that can only record the absolute minimum
of (for sake of argument) 3" of arc, how then will a lens that can resolve
1" of arc be recorded on that sensor?

If you have a sensor that can record 1" of arc, how then can a lens that
can only resolve 3" of arc record 1" of arc on that sensor?

You will always be limited by your weakest resolution link. Now if you add
in antialiasing masks, printer limitations, and the limits of the human eye
depending on viewing distance, then the resolution limits climbs
exponentially.

You're an idiot pretend-photographer troll. Plain and simple. Proved 100%.

You ARE the weakest link.

throwing a dead goat under its troll's bridge to see if it'll go feed on
that

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
a techie sort of question about p&s cameras and optical viewfinders albert Digital Photography 9 December 15th 08 08:03 PM
A meter math question Steven Woody 35mm Photo Equipment 7 April 11th 07 04:51 PM
help with aperture math Beach Bum Digital SLR Cameras 18 February 15th 06 03:18 AM


All times are GMT +1. The time now is 06:59 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 PhotoBanter.com.
The comments are property of their posters.