Hi Mike:

No, I do not support,"a resolution of 4 lp/mm delivered to the final
image, after magnification, to be sharp enough", for my. "taste."

In my (3.7X) MF viewer, with 68mm lenses, I CAN SEE 40 lp/mm, and
consider 24 lp/mm as being adequately sharp. 254/68=3.7X 24 lp/mm
divided by 3.7 = a theoretical 6.5 lp/mm ! Using Fuji Velvia 50 film.

You did say, "I don't actually know what resolution I am achieving after
magnification in the viewer...."

In have little faith in reverse engineering.


I am still waiting to hear why using f/32 will not be permit one to
produce usably sharp MF stereo images.


Best regard,

DON

Hi Don,

At 11:16 PM 11/14/2006, you wrote:

No, I do not support,"a resolution of 4 lp/mm delivered to the final
image, after magnification, to be sharp enough", for my. "taste."

In my (3.7X) MF viewer, with 68mm lenses, I CAN SEE 40 lp/mm, and
consider 24 lp/mm as being adequately sharp. 254/68=3.7X 24 lp/mm
divided by 3.7 = a theoretical 6.5 lp/mm ! Using Fuji Velvia 50 film.

OK.  I thought perhaps you considered 4 lp/mm to be "sharp enough" because my views are considered by many to be "sharp enough" and more, and they were all created with a strict adherence to DoF calculations using a CoC diameter of 0.03 mm - to support a desired resolution of 7.6 lp/mm after magnification, as calculated by my simply taking the reciprocal of lp/mm on-film to get the CoC.

Were I to use your formula for doing the conversion, the 0.03115 mm CoC's I've used for all my DoF calculations would equate to only 3.8 lp/mm after magnification.  You've just stated that you would not consider 4 lp/mm, delivered to the final image, to be sharp enough.  I agree.  That's why I chose a resolution of 7.6 lp/mm.

Do you see the paradox your formula creates?  Your formula mandates that I should have been using a CoC that's half the size of the one I've been using to create images that support a resolution of 7.6 lp/mm after magnification.   My images are about as sharp as sharp gets, so... am I only getting a "not sharp enough" 3.8 lp/mm after magnification or is your formula wrong?

For a short while, you had a protagonist that started a thread with me off-list, who has since declared that we are both wrong.  But while he was on his initial tack of agreeing with your contention that two CoC's equate to each line pair instead of just one, he simultaneously argued (and continues to argue) that no viewer can deliver more than 4 lp/mm to the eye (when you take into account all the factors that degrade resolution throughout the entire system - camera lenses, film, defocus, film flatness issues, camera motion, viewer lenses, etc.)  

So, this fellow believes that the sharp as sharp gets images I produce are actually only delivering 4 lp/mm.  And that conviction correlates with your formula much better than your conviction (and mine) that we can enjoy resolutions much higher than 4 lp/mm in the viewer. 

Again, if my views are delivering more than 3.8 lp/mm in the viewer, then you're formula is wrong to suggest that my CoC's should be half the size I've been using.

I am still waiting to hear why using f/32 will not be permit one to
produce usably sharp MF stereo images.

Did you see my two responses to Sam?

In short, it depends on the what magnifications a viewer can achieve and just what resolution you hope to support in the viewer.  In the thread I had with Sam, I agreed not to use math, but to answer your question, I'll not refrain from diving into it:

The aperture at which diffraction becomes visible can be obtained by working backwards from your anticipated enlargement factor and desired resolution in the viewer (or at the print):

Maximum N = 1 / desired resolution / enlargement factor / 0.00135383

Where did I get the constant 0.00135383? See the section on diffraction in David Jacobson's Lens Tutorial:

http://www.graflex.org/lenses/photographic-lenses-tutorial.html

When I plug in a desired resolution of 7.6 lp/mm (a subjective choice) and an enlargement factor of 4.21x (78mm lenses of my SaturnSlide focused to an image distance of 10 inches for maximum magnification), I get f/23 as the smallest aperture I can use.  Stopping down any further would cause diffraction's Airy disks to grow large enough to inhibit my desired resolution of 7.6 lp/mm.

If instead, I used the formula above, plugging in a desired resolution of 7.6 lp/mm and an enlargement factor of only 3.39x (75mm lenses of the 3DWorld STL viewer focused at Infinity), I would get a more lenient f/29 (almost f/32).

Now if I also lowered my resolution requirement from 7.6 lp/mm to say, 6 lp/mm, again using the 3.39x enlargement factor of the Infinity-focused 3DWorld STL viewer, I would find myself able to stop down to f/36 (well past f/32).

Keep in mind that these thresholds are the apertures at which diffraction will only just BEGIN to inhibit your desired resolution, but... you only have to stop down two stops below the calculated stop to cut your desired resolution in half.

Also keep in mind that many other factors can interfere with achieving your desired resolution.  This discussion only deals with quantifying the impact that diffraction alone has on resolution.  Think of this as one link in the chain.  As long as every link supports your goal resolution, you'll achieve your goal resolution.  In practice, it's impossible to control all the links in the chain, but that shouldn't give us an excuse to weaken the links we CAN control.

Mike Davis

Hi Mike:

Again, why, "so many insignificant digits"?

"....the 0.03115mm CoC...." Why not 0.03mm ?

"Maximum N....0.0013583...." Why not 0.001 ?

How do you know that you are seeing an effective resolution of 4 lp/mm
in your stereo images, in your MF stereo viewer ?

I was not aware that you new what resolution you were seeing, in your MF
Saturn viewer.

How did you determine that your MF viewer produces a magnification of
4.1X, not 4.0X or 4.2x or whatever ?

As regards to using f/32, I have seen many MF stereo slides taken at
f/32, taken by both Sam Smith and by Bob Clark. I don't recall seeing
any lack of sharpness.

Incidentally, Modern Photography published their resolution test results
of a Nikon f/2.8, 90mm lens which produced a resolution, (on Kodak T Max
100 film, developed in D 76), of 49 line pairs per mm at f/32. More
than enough for hi-res MF stereo slides, IMO. So much for theory.

Best regards,

DON













I am puzzled by the need for shooting MF stereo images using f/45 with a
twin lensed stereo camera. My understanding is that a 80mm lensed
camera will provide an on film deviation of about 2.0mm at f22! Who
wants excessive on film deviation, if f/45 is needed ?

Hi Mike:

Apparently, as of 4-13-06, you were in agreement with my view as to the
relationship between circles of confusion, (CoC), and line pairs per mm,
(lp/mm).***

When one photographs a standard National Bureau of Standards resolution
test chart, (from a distance of 26 x the fl of the lens), the 12 lp/mm
section, of the film, shows 24 individual, B&W lines per mm. 12 black
and 12 white lines, (each of the same width).


On 4-13-06, you posted the following:

"The brightness within the CoC is constant. If we use the criterion
that two points are resolved when their CoC's do not overlap....then the
resolution is related to the diameter of the CoC by R=1/c."

"This is the number of non-overlapping CoC's that can fit in a unit length."

"If c is expressed in millimeters, the R represents the number of line
pairs per mm (lp/mm)....We have considered two bright lines separated by
a dark line."

***"Each element consists of a dark line and a bright line. The
separation BETWEEN each element is 'c'."

(Is this not what I have been saying ?) ('c') represents CoC).

"A source of confusion is that some authors consider a line pair (a
dark line and a white line to be two lines, so they would use R=2/c.
This corresponds to the number of pixels." (Ridiculous, IMO)

The diameter of the CoC must be of the same width as is the width of the
white line or of the black line on the NBS resolution test chart.


My version of an example, posted by Brian, on 4-9-06

<-------12 lp/mm------->
XOXOXOXOXOXOXOXOXOXOXOXOX x= The vertical black line
XOXOXOXOXOXOXOXOXOXOXOXOX O= The vertical white line.
XOXOXOXOXOXOXOXOXOXOXOXOX
XOXOXOXOXOXOXOXOXOXOXOXOX
XOXOXOXOXOXOXOXOXOXOXOXOX

XO= a line pair.
----------

Incidentally, I believe that your airy disk formula is no longer
applicable to modern optics similar to the way that the cosine to the
4th power law no longer applies to modern optics since the advent of the
Schneider Super Angulon lens. How else can a modern lens produce 53
lp/mm at f/32, on T Max 100 film.

Ask the 35mm macro 3d shooters, as to whether or not they are happy with
the results that they get, even at f/105, contrary to the, alleged,
'airy disk' problem.

Best regards,

DON




































































































































































XOXOXOX

Don,

At 07:51 AM 11/18/2006, you wrote:

>Hi Mike:
>
>Apparently, as of 4-13-06, you were in agreement with my view as to the
>relationship between circles of confusion, (CoC), and line pairs per mm,
>(lp/mm).***
>
>When one photographs a standard National Bureau of Standards resolution
>test chart, (from a distance of 26 x the fl of the lens), the 12 lp/mm
>section, of the film, shows 24 individual, B&W lines per mm. 12 black
>and 12 white lines, (each of the same width).
>
>On 4-13-06, you posted the following:

-------------------------

>"The brightness within the CoC is constant. If we use the criterion
>that two points are resolved when their CoC's do not overlap....then the
>resolution is related to the diameter of the CoC by R=1/c."
>
>"This is the number of non-overlapping CoC's that can fit in a unit length."
>
>"If c is expressed in millimeters, the R represents the number of line
>pairs per mm (lp/mm)....We have considered two bright lines separated by
>a dark line."
>
>***"Each element consists of a dark line and a bright line. The
>separation BETWEEN each element is 'c'."

-------------------------

>(Is this not what I have been saying ?) ('c') represents CoC).

If you are asking me, "Doesn't the quoted text support my (Don's)
contention that we should equate two CoC diameters to one line pair (2 *
CoC = 1 * lp/mm) ?", my answer is "No."

The first paragraph of the material you quoted makes this
clear. Specifically, " ... the resolution is related to the diameter of
the CoC by R=1/c."

>"A source of confusion is that some authors consider a line pair (a
>dark line and a white line to be two lines, so they would use R=2/c.
>This corresponds to the number of pixels." (Ridiculous, IMO)

Don, it sounds ridiculous because of the way it's worded, but that author,
Q.-Tuan Luong, and many other people, including me, think of a line pair as
a single unit of data. Read it again with that in mind (whether you accept
it or not) and the sentence will at least make sense.

By the way, the text you've quoted from my 4/13/06 post, can be found at
this page, on Q.-Tuan Luong's large format photography
site: http://www.largeformatphotography.info/fstop.html

>The diameter of the CoC must be of the same width as is the width of the
>white line or of the black line on the NBS resolution test chart.
>
>My version of an example, posted by Brian, on 4-9-06
>
><-------12 lp/mm------->
>XOXOXOXOXOXOXOXOXOXOXOXOX x= The vertical black line
>XOXOXOXOXOXOXOXOXOXOXOXOX O= The vertical white line.
>XOXOXOXOXOXOXOXOXOXOXOXOX
>XOXOXOXOXOXOXOXOXOXOXOXOX
>XOXOXOXOXOXOXOXOXOXOXOXOX
>
>XO= a line pair.
>----------

I understand that one white line and one black line, together, make one
line pair.

Consider this seat-of-the-pants, real world illustration that supports the
majority contention that we should equate only one CoC per line pair:

I think we can agree that the 0.03 mm "standard" CoC diameter used for the
35mm format in many different types of DoF scales, charts, and calculators
is too "soft" to satisfy our requirements for making 8x
enlargements. Therefore, I think it safe to say that we both find the
"standard" 0.06 mm CoC diameter, commonly used with 6x6cm format DoF
calculations, to be equally "soft" if the intent is to make an 8x
enlargement.

This is why so many people, using the seat-of-their-pants (not my formula,
nor your formula), adhere to the practice of stopping down one or even two
additional stops beyond that indicated by the DoF scales engraved on their
lenses, when they intend to make an 8x enlargement.

I think we can agree that 0.06 mm is too large a CoC diameter for making 8x
enlargements from the 6x6cm format.

Using a MF lens barrel engraved with DoF scales calculated to deliver
maximum CoC diameters of 0.06 mm, if we decided to stop down TWO full stops
below the indicated stop for a given subject space, the resulting maximum
CoC diameter would be 0.03 mm instead of 0.06mm. I'm hoping you will agree
that this is a fairly aggressive action, but not at all unwarranted, if it
is our intent to make an 8x enlargement from the 6x6cm format.

Now consider this: How about if we were to tighten our requirements even
further by stopping down TWO full stops below the indicated stop -AND-
using an enlargement factor of only 4x instead of 8x? At a given viewing
distance, that 4x enlargement will appear TWICE as sharp (ignoring factors
other than CoC diameter) as would an 8x enlargement. Right?

Thus, we could say that stopping down two stops below the stop indicated by
a DoF calculation done with 0.06mm CoC's yields 0.03 mm CoC's on-film, but
cutting our enlargement factor in half, gives us a degree of "sharpness"
that could only be achieved in an 8x enlargement only by limiting on-film
CoC diameters to 0.015 mm (half of 0.03 mm). This is the equivalent of
stopping down FOUR full stops below that indicated by a lens barrel DoF
scale that was calculated to deliver 0.06 mm maximum CoC diameters.

Do you know any MF shooters who routinely stop down FOUR stops below that
indicated by "standard" 0.06 mm DoF scales on their lens barrels when their
intent is to make 8x enlargements?

I exercise precisely that same degree of aggressiveness when I use 0.03mm
CoC diameters to perform DoF calculations with the intent to make 4x
enlargements (via my stereo viewer).

Just think about that for a moment before we proceed. When I use DoF
calculations that deliver a 0.03mm maximum CoC diameter on-film, then view
those chromes at only 4x magnification, my choice to use 0.03 mm CoC's is
IDENTICAL to an MF shooter who wants to make an 8x enlargement choosing to
stop down FOUR stops below the stop indicated on his lens barrel DoF scales
(assuming those DoF scales were calculated to the MF standard of 0.06 mm).

Punchline: When I use a maximum CoC diameter 0.03mm in DoF calculations
that govern how I shoot for my 4x MF3D viewer, I am pursuing "sharpness"
with fervor.

Now let's go back to our formulas for calculating the lp/mm seen, after 4x
magnification, when the maximum CoC diameter captured to film is only 0.03 mm:

Mike's formula:
lp/mm supported on-film = 1 / 0.03 mm = 33 lp/mm
lp/mm supported in the 4x viewer = 33 / 4 = 8 lp/mm

Don's formula:
lp/mm supported on-film = 2 / 0.03 mm = 67 lp/mm
lp/mm supported in the 4x viewer = 67 / 4 = 17 lp/mm

Wow? 17 lp/mm is quite a bit higher than the human eye is capable of
resolving, isn't it Don?

I know you don't believe the human eye can appreciate 17 lp/mm, so is my
use of 0.03mm needlessly aggressive or is your formula wrong?

That's the paradox your formula creates, as I've mentioned twice before in
this thread.

If I start with a desired resolution of 8 lp/mm after 4x magnification, and
use my formula to calculate the CoC needed for a 4x enlargement, I get 0.03
mm, a CoC that's already so aggressive, it's equivalent to someone who
wants to make an 8x enlargement stopping down FOUR stops below the stop
indicated on a "standard" DoF scale.

But with your formula, if I set out to achieve that same desired resolution
of 8 lp/mm after 4x magnification, I would have to use a maximum CoC
diameter of only 0.015 mm. That would be the equivalent to someone who
wants to make an 8x enlargement stopping down SIX full stops below the stop
indicated on a "standard" DoF scale. That would require shooting at f/22
when f/2.8 is indicated, to produce an 8x enlargement.

If this seat-of-the-pants approach hasn't convinced you, I've nothing
further to add. As with our discussion regarding the effects of
diffraction, I'll leave it to you to close the thread with any final comments.

[snip]

>Best regards,
>
>DON
>
>XOXOXOX

Don, that is the funniest thing I've ever seen in any of your posts! (Are
those kisses and hugs, or line pairs?)

You DO have a sense of humor!

:-)

Mike Davis

I let the factory know that I had fixed the aperture
inaccuracies in my camera. They responded a couple days later
and asked for the lens serial # because they wanted to trace
out the origin of the assembly problem. So they do have
concern over the quality of the camera as well as making
continuous improvements in what is probably a very low volume
product.

A question, what are the electrical contacts in the prism for?
The led's for the exposure meter are under the focusing
screen.

Sam, you asked us to test our prism focusing. Mine viewed in
focus which you said was a problem. On the camera, the split
screen, prism circle, and ground glass seem to all go into
focus at the same spot. Does that mean I still have a problem
or that it is inaccurate when it appears to be in focus?

I would really like to take some handheld shots as I am not one
to haul around sturdy tripods. I thought I could just push
process Provia 1 stop and that would make it possible over a
reasonable exposure range. I never tried this before and I
wondered how film appears different when push processed? Also,
can the new Velvia 100 be pushed?

Dale Yingst

Dale Yingst wrote:

> A question, what are the electrical contacts in the prism for?

I suspect they transmit the f/stop back to the camera body.
Exposure is dependent on
Film speed
Shutter speed
Aperture

Film speed is set on the top knob
Shutter speed is set there, too
Aperture setting comes from the lens

> I never tried this before and I
> wondered how film appears different when push processed?

I have pushed Provia without problems.
My processor would only push one stop so I have never tried
pushing it farther.

--
________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

Hi Mike:

Please tell me, when and where did I ever say that, "2/0.03mm = 67
lp/mm" ???

I have stated that 0.015mm CoC equals 33 lp/mm.

Your previous post said: "We have considered two bright lines sepsarated
by a dark line. Each element consists of a dark line and a bright
line. The separation between each element is c."

I assume that the separation refers to the space between the black
lines, or the space between the white lies, as there is no reason, IMO,
for there be a space between the paired black and white lines, when I
photograph a resolution test chart.

How is it possible that a pair of B&W lines could provide any resolution ?

The definition of, 'c', in the above post was- "CoC in mm."
Therefore, CoC equals the distance between the pair of black lines, or
the distance between the pair of white white lines. Therefore, 33
lp/mm = 1/66 of a mm = 0.015mm CoC, not your, asserted, 0.03mm CoC.

Incidentally, I have read that the DoF lines on your Mamiya 7 lenses are
based on a resolution of 15 lp/mm, which if according to your theory,
should give you about 3.7 lp/mm in your viewer.

I have my doubts.


Best regards,

DON

Don,

At 07:39 PM 11/18/2006, you wrote:

>Please tell me, when and where did I ever say that, "2/0.03mm = 67
>lp/mm" ???

You never explicitly wrote, "2/0.03mm = 67 lp/mm" - it was just an example
that embodies your contention that two CoC's are equated to one line pair.

Mike Davis

Don,

>At 07:39 PM 11/18/2006, you wrote:
>
> >Please tell me, when and where did I ever say that, "2/0.03mm = 67
> >lp/mm" ???

You were right to question my having said that your formula would convert
0.03mm to 67 lp/mm.

I revisited your protest and have discovered that I misquoted your formula.

Your formula would do the conversion like this:

1 / 0.03 mm / 2 = 17 lp/mm

My formula would do the conversion like this:

1 / 0.03 mm = 33 lp/mm

I apologize for the angst that caused you, but can assure you it was an
honest mistake. Now, having reexamined my "seat-of-the-pants" argument, I
still find it makes sense up until the point I tried to compare our
formulas and misquoted yours.

Here are the closing paragraphs of that argument, edited to use your
formula correctly:

--------

Do you know any MF shooters who routinely stop down FOUR stops below
that indicated by "standard" 0.06 mm DoF scales on their lens barrels when
their intent is to make 8x enlargements?

I exercise precisely that same degree of aggressiveness when I use
0.03mm CoC diameters to perform DoF calculations with the intent to make
4x enlargements (via my stereo viewer).

Just think about that for a moment before we proceed. When I use
DoF calculations that deliver a 0.03mm maximum CoC diameter on-film, then
view those chromes at only 4x magnification, my choice to use 0.03 mm
CoC's is IDENTICAL to an MF shooter who wants to make an 8x enlargement
choosing to stop down FOUR stops below the stop indicated on his lens
barrel DoF scales (assuming those DoF scales were calculated to the MF
standard of 0.06 mm).

Punchline: When I use a maximum CoC diameter 0.03mm in DoF calculations
that govern how I shoot for my 4x MF3D viewer, I am pursuing "sharpness"
with fervor.

Now let's go back to our formulas for calculating the lp/mm seen, after 4x
magnification, when the maximum CoC diameter captured to film is only 0.03 mm:

Mike's formula:
lp/mm supported on-film = 1 / 0.03 mm = 33 lp/mm
lp/mm supported in the 4x viewer = 33 / 4 = 8 lp/mm

Don's formula:
lp/mm supported on-film = 1 / 0.03 mm / 2 = 17 lp/mm
lp/mm supported in the 4x viewer = 17 / 4 = 4 lp/mm

Wow? 4 lp/mm is quite a bit lower than the human eye is capable of
resolving, isn't it Don?

I know you don't believe the human eye can appreciate only 4 lp/mm, so is
my use of 0.03mm insufficiently aggressive (remember, it's got me stopping
down four stops below what a 0.06 mm calculated DoF scale would indicated)
or is your formula wrong?

That's the paradox your formula creates, as I've mentioned twice before in
this thread.

If I start with a desired resolution of 8 lp/mm after 4x magnification, and
use my formula to calculate the CoC needed for a 4x enlargement, I get 0.03
mm, a CoC that's already so aggressive, it's equivalent to someone who
wants to make an 8x enlargement stopping down FOUR stops below the stop
indicated on a "standard" DoF scale.

But with your formula, if I set out to achieve that same desired resolution
of 8 lp/mm after 4x magnification, I would have to use a maximum CoC
diameter of only 0.015 mm. That would be the equivalent to someone who
wants to make an 8x enlargement stopping down SIX full stops below the stop
indicated on a "standard" DoF scale. That would require shooting at f/22
when f/2.8 is indicated, to produce an 8x enlargement.

--------

Please note that I've made no edits to the last two paragraphs,
above. They were correct despite my having used the wrong formula in the
preceding paragraphs.

Thus, my argument stands: To support a desired resolution of 8 lp/mm after
4x magnification, My formula already has me stopping down FOUR stops from
that indicated on a 0.06 mm calculated DoF scale. Your formula would have
me stop down SIX stops from that indicated on a 0.06 mm calculated DoF
scale. If the lens barrel indicates that f/2.8 will provide sufficient
DoF, your formula would have us use f/22 to achieve 8 lp/mm after 4x
magnification. Doesn't that just *feel* wrong to you
(seat-of-the-pants)? My views already exhibit extremely "sharp" Nears and
Fars - consistently - and that's not just my opinion. Does it make sense
to stop down TWO additional stops because your formula says my 0.03 mm CoC
is supporting only 4 lp/mm after magnification. My formula says my 0.03 mm
CoC is supporting 8 lp/mm in the viewer. Many people, including you, would
say that 8 lp/mm is a lot closer to the limit of human resolving power than
4 lp/mm.

Mike Davis

Hi Mike:

I have long been bothered when reading CoC numbers such as: 0.03115mm,
or even 0.00.0013383mm. How can any of your CoC numbers be
considered as being so precise ?

Have you ever seen any CoC's on your stereo slides that have a diameter
as small as 0.03115mm, (slightly over three one hundredths of a mm) ?

Can you see any difference between a CoC that measures 0.02mm, and one
that measures 0.04mm in diameter ?

I have my doubts,concerning your use of numbers that indicate exagerated
precision, such as 0.03115mm, 7.625mm, 4.21x magnification, and 32
lp/mm.

You mentioned that, "I use a CoC of 0.03115 to support a resolution of
7.625mm after 4.21X magnification in my adjustable-focus Saturn Slide
viewer."

Have you ever seen or measured a CoC which was 0.03115mm in diameter ?

I am curious as to how you were able to determine that the actual
resolution on your stereo slides was 32 lp/mm ?

I am also curious as to how you were able to determine that your Saturn
viewer provides a magnification of, "4.21X", and not 4.22X or whatever ?

How do you know that when you are using your Saturn MF viewer that you
are actually seeing a resolution of, "7.625mm", lp/mm, and not 7 or 8
lp/mm ?

The above proposals appear, to me, to be a case of reverse engineering
!
--------

Because I do not trust theoretical numbers, I take stereo slides which
include N.B.S. resolution test charts. I can determine what the on
film resolution is, at different distances, at different f/stops. The
numbers are not theoretical. My charts indicate resolution numbers,
of 12,14,17,20,24,28,34,40,48,56,68 and 80 lp/mm.

I am not able to see any significant difference 7, 8, or 9 lp/mm on my
slides as the Fuji films I use is not capable of showing such slight
differences, IMO. By changing the distance to the test charts, I can
get different resolution numbers.

50 some years ago, while I was at Boeings, the Air Force required that
both air speeds and altitude numbers had to be accurate to within two
decimals.

Boeings solved the problem by starting with approximate metric numbers
and converted them to MPH and to feet, getting all of the,"precise
numbers", required.

Best regards,

DON

Don,

At 12:25 PM 11/22/2006, you wrote:

>Hi Mike:
>
>I have long been bothered when reading CoC numbers such as: 0.03115mm,

Recent posts evidence my having made an effort to accommodate the fact that
you are bothered by my use of insignificant digits.

Getting back on topic (see the subject header), we were discussing which of
two formulas should be used to convert a CoC diameter in mm to a resolution
in lp/mm:

At 09:26 AM 11/19/2006, I wrote:

>Mike's formula:
>lp/mm supported on-film = 1 / 0.03 mm = 33 lp/mm
>lp/mm supported in the 4x viewer = 33 / 4 = 8 lp/mm
>
>Don's formula:
>lp/mm supported on-film = 1 / 0.03 mm / 2 = 17 lp/mm
>lp/mm supported in the 4x viewer = 17 / 4 = 4 lp/mm

I've not seen a response to the "seat-of-the-pants" argument I presented in
my last post to this thread (specifically the portion seen below). You
don't have to respond if you don't want to, but I would appreciate it.

At 09:26 AM 11/19/2006, I wrote:

>If I start with a desired resolution of 8 lp/mm after 4x magnification, and
>use my formula to calculate the CoC needed for a 4x enlargement, I get 0.03
>mm, a CoC that's already so aggressive, it's equivalent to someone who
>wants to make an 8x enlargement stopping down FOUR stops below the stop
>indicated on a "standard" DoF scale.
>
>But with your formula, if I set out to achieve that same desired resolution
>of 8 lp/mm after 4x magnification, I would have to use a maximum CoC
>diameter of only 0.015 mm. That would be the equivalent to someone who
>wants to make an 8x enlargement stopping down SIX full stops below the stop
>indicated on a "standard" DoF scale. That would require shooting at f/22
>when f/2.8 is indicated, to produce an 8x enlargement.
>
>[snip]
>
>Thus, my argument stands: To support a desired resolution of 8 lp/mm after
>4x magnification, my formula already has me stopping down FOUR stops from
>that indicated on a 0.06 mm calculated DoF scale. Your formula would have
>me stop down SIX stops from that indicated on a 0.06 mm calculated DoF
>scale. If the lens barrel indicates that f/2.8 will provide sufficient
>DoF, your formula would have us use f/22 to achieve 8 lp/mm after 4x
>magnification. Doesn't that just *feel* wrong to you (seat-of-the-pants)?
>
>My views already exhibit extremely "sharp" Nears and Fars - consistently -
>and that's not just my opinion. Does it make sense to stop down TWO
>additional stops because your formula says my 0.03 mm CoC is supporting
> only 4 lp/mm after magnification. My formula says my 0.03 mm CoC is
>supporting 8 lp/mm in the viewer. Many people, including you, would
>say that 8 lp/mm is a lot closer to the limit of human resolving power than
>4 lp/mm.

Mike Davis

Unless someone else prefers otherwise, I would appreciate it if this
topic could be continued offlist. I have not seen a single third party
respond to an interest in this somewhat off topic train of emails.

If someone else would like it continued, please speak up.

Sam (moderator)

Hi Mike:

IMO, you have the cart before the horse.

You are in my opinion, starting with an unknown factor.

How do know that your viewer provides 4X magnification ?

Also, how do you kmnow that your stereo slides are presenting a
resolution of 32 line pairs per mm ?


Best regards,

DON

Sam,

Dale asked if anyone had prepared a DoF chart for the TL-120. I am the
only person who responded to his request. I've been defending that
response ever since, but one complaint is all I need to terminate the
thread - my half of it, at least.

Thanks for putting us out of our misery,

Mike Davis

Sam Smith wrote:

> If someone else would like it continued, please speak up.

I have no problem with the continuation here, on-list. TWith
that said, as moderator you are the boss.

The fact that I haven't commented on them doesn't mean I
haven't read them.

--
John Thurston
Juneau Alaska
http://stereo.thurstons.us

I haven't responded to any postings because frankly, I don't know what
the heck you guys are talkin' about! Depth of field for me has always
been to shoot at the smallest aperture and focus for the best DOF, the
end. All this math doesn't add up for me (forgive the pun):-)

Arthur Payson

On Nov 22, 2006, at 7:56 PM, John Thurston wrote:

> Sam Smith wrote:
> > If someone else would like it continued, please speak up.
>
> I have no problem with the continuation here, on-list. TWith
> that said, as moderator you are the boss.
>
> The fact that I haven't commented on them doesn't mean I
> haven't read them.
>
> --
> John Thurston
> Juneau Alaska
> http://stereo.thurstons.us
>
>
>

--- In MF3D-group@yahoogroups.com, John Thurston wrote:

>
> Sam Smith wrote:
> > If someone else would like it continued, please speak up.
>
> I have no problem with the continuation here, on-list. TWith
> that said, as moderator you are the boss.

No I'm not. I merely set up the list. What is relevant to it needs to
be decided by the members themselves. The original topic is entirely
relevant and is strongly encouraged to continue. Challenges should
however be considerate and perhaps a tad compromising. It keeps others
interested in participating.

I would strongly encourage members to permanently post relevant info
(like COC data, spread sheets or charts) in the FILES section of this
discussion forum. That way it will be there to use at any time. I
myself completely lost track as what the original information was, and
am too lazy to sort through 20 plus emails of the same heading to find
out!

Sam