4x5 Ultra Fine Focusing and Calibration

[rvhalejr]

... Vacuum Grease...

...largeformatphotography.info/forum/showthread.php?p=1350#post1350

With the large amount of *depth of focus* inherent in large format, I seriously doubt that a vacuum film back would make much of a difference.

[rvhalejr]

I am sorry i can not offer anything else... so, enjoy your journey...

Au contraire .,.

...largeformatphotography.info/forum/showthread.php?p=430475#post430475
...largeformatphotography.info/forum/showthread.php?p=430476#post430476
...largeformatphotography.info/forum/showthread.php?p=430476#post430477

Ref post430475 Re: Top-end digital concerns {Intro into Spreadsheet and Plots}

> ... remember, the f #'s and their MP's are MAX. POSSIBLE recorded resolutions, not min. resolutions. This also represents the resolution at the POF (Point of exact Focus). So this assumes you are shooting a FLAT test target or an infinity scene, both having a flat focal plane. When you introduce depth into the equation, the near and far points will always have less resolution than the POF, (up to a point) so the f# and MP's values I offered above, you can cut them by 20 - 50% (estimate) based on the amount of depth you have in a scene. This is why the 568 MP values are so far from reality.... real world depth MP values for 8x10 at f45 can be in the 40 - 90 MP range, based on the amount of depth and f stop used. (more on this below) There has been several web examples of 40 MP digital captures nearly matching 8x10 film - same composure being compared...(color, not B&W) .... and when there is enough depth in the scene the gap can be surprisingly small...but shoot infinity subjects or FLAT subjects, and 8x10 film will destroy a 40 or 60 MP back. This is why the comparisons are all over the map... the devil is always in the details....

When I plot 4x5 @ f22 on a cy/mm vrs. rack and pinion distance (fl = 90mm so x-axis points are roughly at 78, 82, 86, 90, 94, 98, 102mm) I get a wedge shape (it looks like an inverted V, or roof pitch from the side) with the POF being the highest point (maxima and intersectoion of two somewhat straight lines). The line leading up to the POF (at points < 90mm) has a positive slope, The line past the POV (at points > 90mm) has a negative slope described as y=mx+b ...

When I plot 4x5 @ f32 the shape of the wedge becomes flatter due to DoFocus,
Let y'=m'x'+b'

When I plot 4x5 @ f45 the shape of the wedge becomes flatter due to DoFocus,
Let y''=m''x''+b''

and the differences between f22 and f32' and f45'' variables (and b the constant) should generally be ???

>
Here is a simple example that hopefully will bring these numbers into reality.....

We shoot a flat target at f45 with 8x10 color film with 60 lp/mm MTF at the given contrast value of the target. We assume perfect film alignment, focus and diffraction limited lens at f45, single focal plane.... OK?

AT best, we can resolve:

1/(1/33+1/60) = 21 lp/mm

(1500/45 = 33 lp/mm aerial rez)

This means a 30 lp/mm target at the film plane will NOT be resolvable under magnification...it will appear as a blob, vs. cleanly defined lines. It means 20 lp/mm target on the film will appear barely discernible....not a blob, but not sharp. A 10 lp/mm target will look sharp, and a 5 lp/mm target will look razor sharp. This is MTF at work... the finer the detail, the less contrast that is Transfered (hence the T, in MTF) This testing procedure is as old as the hills.... no voodoo math here.

Where does 1/33 come from ???

Where does 1500 come from ???

If we use a three targets:
(1) at near focus (probably near the ground)
(2) in between and to the side (the POF)
(3) at the hyper-focal distance (probably on the top of a light stand) and record three cy/mm values, should this data set (and the plane they define) still be called aerial ???

Thanks before hand,

R. (a sign of joy, not disrespect)

[bglick]

> Au contraire .,.

I stopped commented on your mis guided journey..... my posts after that point, were about generic issues... got it?



> I get a wedge shape (it looks like an inverted V, or roof pitch from the side) with the POF being the highest point (maxima and intersectoion of two somewhat straight lines).


This seems to be off from your previous journey, so i will comment. The Depth of focus at the image plane is equal, in front of, and behind the image plane, so perfect wedge is the ALWAYS the resultant plot....... but why plot it? Once you comprehend the definition of DofFocus, its always the same?


> Where does 1/33 come from ???

Your quote above shows where it comes from?? 1500 comes from the avg. wavelengths of light, that determines the MAX. aerial resolution value a lens can project..... 1500 / f stop = max aerial resolution. .... mentioned several times... research "Apt. Diffraction limits" to understand this aspect, again, 100 year old accepted formula, nothing new here either.... It's obvious, after all these posts, you are "now" just starting to investigate 1/R.... ??? carriage in front of the horse? :-)

[rvhalejr]

>
rvhalejr> I get a wedge shape (it looks like an inverted V, or roof pitch from the side) with the POF being the highest point (maxima and intersection of two somewhat straight lines)...

The Depth of focus at the image plane is equal, in front of, and behind the image plane, so perfect wedge is the ALWAYS the resultant plot....... but why plot it? ... :-)

"Complexity is our enemy", differentiation between stops might be enlightening, perhaps second derivatives and the previous question about 3 simultaneous targets .,.

Bummer, I just realized we cannot upload xls files here .,.

[rvhalejr]

...largeformatpro.com/examples_color.html

How many MP ?

Attached is an example of post scan grain reduction
est. image data loss 10&#37; (signal)
est. grain data loss 90% (noise)

Also distributions in sky pre/post

[rvhalejr]

Ref ...pbase.com/bglick/lens_tests

How many MP ?

Attached is an example of noise (grain) measurement as compared to the same area when it is ideally perfect.

This is a first order approximation.

The Original/Idealized under the curve ratio is ==
1/((base e) + (gamma/base e))

Where gamma is 2.2 (Windows) 1.8 (Mac) or 1.4 (some Archival Master Files more or less, the limits for gamma are 2.5 and 1) and base e == 2.71

This example (DSLR) exhibits the ratio similar to the previous Drum Scan example (Over-Scanned at 3200cy/mm yielding 320MP SOP - Standard Operating Procedure) after heavy post-scan processing and noise (grain) reduction.

A better Approximation would have targets in each (film and digital example) with the same cy/mm value.

The same cy/mm (or lp/mm) value is unlikely to be the same so a compensating factor would be used on the film and digital data to normalize.

There is no relationship implied here as to the 1/R, diffraction limits and airy disks as contrasted with the mini-camera-obscura and pinhole modeling of the different film (and digital) formats.

Individual point sampling (in the past) has verified that this method is
similar to the results obtained when calculating the standard deviation,
rms grain values or the generally accepted S/N ratios.

[rvhalejr]

….cityastronomy.com/rez-mag-contrast.htm

Let HRDS == One of the following limits Hale, Rayleigh, Dawes or Sparrow

Hale's Limit (2.71/2) or 1.36 550 • 0.206/D = resolution "arc.
(ex: 1.36 550 • 0.206 == 154.1/127mm= 1.213”arc
Simplified: 154.1/D in mm = resolution "arc or 6.06/D in inches
Rayleigh limit: 1.22 • 550 • 0.206/D = resolution "arc.
(ex: 1.22 • 550 • .206= 138.23/127mm= 1.088"arc)
Simplified: 138/D in mm = resolution "arc or 5.45/D in inches
Dawes Limit: 1.025 • 550 • 0.206/D = resolution "arc
(ex: 1.025 • 550 • 0.206 = 116.13/127 = 0.91"arc
Simplified: 116/D in mm = resolution "arc (or 4.56/D in inches)
Sparrow's Limit: 0.94 • 550 • 0.206/D = resolution "arc
(ex: 0.94 •550 • 0.206= 106.50/127mm= 0.839"arc
Simplified: 107/D in mm = resolution "arc (or 4.2/D in inches)

Where
D == Diameter of telescope mirror
ex: n.nn == period, peak-to-peak or trapezoid (OTDR cats eye) like pulse

Resolving power is the ability of the components of an imaging device to measure the angular separation of the points in an object.

ex: 1.213” == 0 degress 0 minutes 1.213 Seconds

1/60*60*60*1.213 == 3.82um

More: ...microscopy.fsu.edu/primer/anatomy/numaperture.html

ref: ...physics.emory.edu/~weeks/confocal/resolution.html

The best resolution for an optical microscope is about 0.2 microns = 200 nm.

The good news is, there's a difference between resolution and "ability to locate the position".

If you have one tiny and isolated fluorescent object, you can often locate the position of that object to better than your resolution. The image of the object will show up as an extended blob, and you can find the "center of mass" of that blob-shaped image. If the blob is N pixels wide and each pixel is M microns across, you can estimate the center of the blob to about M/N accuracy, which often beats the optical resolution. This is a useful trick, but not solving the same problem as resolution. In some cases you can do various tricks to make the spot size bigger (increase N) so that you can locate the center even better. Various experiments I've heard of have claimed to be able to locate the centers of spots to within 10-30 nm using this sort of method.

[rvhalejr]

Ref ...pbase.com/bglick/lens_tests

How many MP ?
...
This example (DSLR) exhibits the ratio similar to the previous Drum Scan example (Over-Scanned at 3200cy/mm yielding 320MP SOP - Standard Operating Procedure) after heavy post-scan processing and noise (grain) reduction.
...

*** Note: 320MP from 4x5 film == 4000 dpi !!! *** TYYYPPPoooo...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(3200 dpi is 200MP from 4x5 SOP)

SNR Noise Reference ...imatest.com/docs/noise.html (Standard Deviation)

The Following Approximates End Product YIELDS for various formats
(DeFocus <= 0 mm; film flatness <= .001 for LF)

Let SNR for 4x5 film = 1/3 (200MP film scan yields about 65MP);
1.75 MP per cm^2 from 3200dpi fluid film scan (10cm x 12.5cm == 125cm^2)
0.58 MP per cm^2 end product yield

Let SNR for 120/220 == 1/2 (33MP/66MP for 645/6x9 yields 16MP/32MP)
1.24 MP per cm^2 from 2800dpi fluid scan
.65 MP per cm^2 end product yield

Let SNR for 35mm film == 2/3 (16MP film scan yields about 12MP)
1.75 MP per cm^2 from 3200dpi fluid film scan
1.24 MP per cm^2 end product yield

=============================================================
See attached Table of Resolution when DeFocus <> 0

1.) An example of how film flatness, precise focusing (with a 35-40x loupe) and
calibration can be important. ref. ...normankoren.com/Tutorials/MTF5.html
for some more uses for loupes .,.

2.) In the table that followed, Lens aberration and resulting
lp/mm values look to be lowfor some quality LF primes that
have good Aberration Balancing.
ref. ...mellesgriot.com/products/optics/fo_6_5.htm

3.) Fairchild Imaging's CCD595 CCD sensor has 85 Megapixels,
9216x9216 8.75 &#181;m pixels; 8.064 cm2 It's designed for aerial
reconnaissance and probably six years old (check the
telescope mirror equations for the size needed to read a
license plate from 250 - 500 miles up on orbit).

4.) Under "Carl Zeiss MTF curves are measured – not just
calculated"

"As far as we can see today Carl Zeiss is still the only
manufacturer to print MTF curves which are measured,
which describe lenses that can actually be purchased,
not just calculated curves of highly ambitious designs
which may exceed the manufacturer's capability of
turning them into reality."
ref ...normankoren.com/Tutorials/MTF2.html#Zeiss

Note: check 120/220 Ziess Lenses .,. (6x7 or 6x9 ?) against Mamiya(s 6x6) .,.

[rvhalejr]

=============================================================
See attached Table of Resolution when DeFocus <> 0

The url to download the spreadsheet is on this page:
...largeformatphotography.info/merklinger-spreadsheet.html


Continuing from the previous post:
ISO 25 4x5 film held very flat and finely focused might yield

Let SNR for 4x5 film = 1/3 (320MP film scan would yield about 107MP);
(10cm x 12.5cm == 125cm^2 for 4x5" film)
(4000dpi == 2.5 MP / cm^2)

2.5 MP per cm^2 from 4000dpi fluid film scan
0.83 MP per cm^2 end product yield

[rvhalejr]

This product is no longer being offered.

Previous customers will continue to receive support.

For Sale:

Loupe and Stands for 4x5 Precision Plenum Photography

Focusing with GG (Ground Glass) is crude and inaccurate.

Offered here is a shimmed plenum and loupe that allows you to verify
that your emulsion plane and focal plane are aligned within .001"
by bringing both into focus simultaneously.

This allows the photographer to validate the camera system and
evaluate details that would not be possible otherwise.

Get the kind of resolution out of your equipment that would make Ansel
Adams cry. Isolate problems, calibrate and utilize equipment at the
highest possible level of performance.

With advances in sheet film scanning (the betterscanning.com fluid
scan film holder of one) you can create high quality 4x5 images that rival
several hundred dollar fluid drum scans.

Using GG is great for composition but almost useless for finely
focused precision photography. Create images reliably and consistantly
that fully exploits the 3200dpi fluid scan resolution with breathtaking
results.

To use the plenum and loupe simply remove the Ground Glass holder.
Once Focused remove the plenum, re-insert the GG and Film Holder
(or 120/220 back) and take the picture.

Satisfaction Guaranteed or Money Back (less shipping)

Pricing Includes Full Documentation and Support

DIY fabrication of the glass and shimming it to the critical dimension.

For normal to near telephoto lenses:
$79.95 for the Loupe (default center of frame stand).

For Wide Angle Angle:
$119 for Loupe and side (of 4x5 frame) stand

$149 for Loupe, side and corner (of 4x5 frame) stand

Ready to go tested shimmed plenums

$49.95 For Glass

$49.95 For Acrylic

Tools for lp/mm Lens Measurement and Profiling
$79.95 for Microscope with Reticule and CS Target.

Transactions will be conducted via ebay and paypal.
Search for "Fine Focusing Loupe" for example listings.
Let me know you saw it here so we can customize your kit.

Shipping is $10, $20 for 4x5 plenums and $30 for 8x10 plenums

Comming soon
$349 4x5 kit with everything for the serious LF photographer
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8x10 plenums are glass only

Still in development
$149 Precision Film Holder (+/- .0005" aligned emulsion plane), USB Black Bag Camera, Documentation and Support

$249 Precision Film Holder (+/- .0005" aligned emulsion plane), Darkroom Night Vision Documentation and Support

$Not Priced yet - Universal upgrade to CCD fluid scanning systems