Very helpful--and great to have the image posted here. Thanks a million!

Well you don't have to worry about that any more, folks.

I've been told "tone it down and no more replies in unestablished user's topics"
So I'm outta here.

It's been fun. Good luck to you all!

A bipod!

I've been told "tone it down and no more replies in unestablished user's topics"
So I'm outta here.

It's been fun. Good luck to you all!

OK, "triangle" a metaphor--I'll buy that..

We'll, I've been told "tone it down and no more replies in unestablished user's topics"
So I'm outta here.

It's been fun. Good luck to you all!

Most air crashes are due to pilot error. That does not make them OK.
Eveyrthing possible is done to reduce the possibility of pilot error,
and the severity of the consequences.

For example, in piston engine aircraft, the knob on a mixture control is a
different shape than the knob on the throttle. Good idea, no?

Sure, dropping and breaking a camera is not an aircrash.
But it sure can spoil your day.

Many once-common types of cameras in use today are no longer
made and so irreplacable. Parts also are no longer made, so much
be cannibalized from another identical camera, or fabricated in a
machine shop.

Also, some of these cameras (even some 35 mm--to say nothing of
large format) are much heavier then those made today. Some
(e.g., the Nikon F) really would stop a bullet (ask Don McCullin!).

Basically, the big Japanese camrea companies only make three
types of camera today:
* DLSRs (OVF)
* Digital, screen on the back (no OVF)
* Digital, screen inside (EFV)

Banished by the big makers are, the TLR, folding camera, box camera,
press camera, field camera, monorail camera, stereo camera, panaramic
camera. -- and anything that uses film (except Fuji's instant film cameras).
(Of course, some there are kludgey cut-and-paste ways to make
paramamas and click-move-click ways o make stereo photos.)

To cut assembly labor costs and stimulate customers to replaced all
their lenses, they'd like to discontinue DSLRs --- hence the heavy
promotion of "mirrorless".

Meanwhile, digital camera sales have declined by more than 70% since
2010, and are currently either flat or growing very slowly. Yet the
last Japaense maker to exit the camera business was Konica Minolta
in 2006 The same number of camera makers are vying for a much
smaller market.

This situation is maintainable only by keeping prices high while cutting
costs. And that won't play well during the next recession.

The future of cameras for photography--not counting cell phones -- is
uncertain. So dropping one can be a big loss.

Strictly speaking, exposure is a scalar quanity: luminance falling
on the film or image sensor times elapsed time: e.g., candelas per square
meter -seconds.

The relationship beween exposure and film density or sensor voltage
and exposure is given by the H-D curve of the particular film or sensor.

This is where ISO comes in. ISO speed is defined by certain
propeties of the H-D curve. An HD curve with a higher ISO value
will producer more density for a given amount of exposure for
over most of its range (the acutal definition is complex--and for a
long time there was no standard fo digital).

What you are talking about is camera exposure settings.

In this sense, exposure is a "space" having 3-dimensions:
Any particular combination of ISO, f-number and shutter
speed is represented as a point in exposure-space.

So it has nothing whatsoever to do with triangles (or
trigonometry) but does have to do with the cardinal number 3
and this 3-space.

Sorry if this is not a sound-bite or a slogan (like "exposure
triangle"). But ya' know, a triangle is a three-sided
polygon -- not any collection of three things.

Good thinking. It pays to use the right screw.

In aircraft, machine screws that must not come loose have holes though their heads,
and are wired in place with "safety wire" made of stainless steel, that is twisted
together like a twist-tie. To remove the screw, you must first cut the safety wire.

The Arca/"Swiss" quick release is strong, but not positive-action. It relies on tightening
a clamping screw---if one doesn't the screw enough, the camera can slide off. I've never
had that happen, but it is possible. Worse, you can't tell by looking if the screw is tight
or loose enough to let the camera slide out.

What it needs is a little latch that needs to be depressed before the camera can be removed.
I like the Arca QR, but it could be much better--and without making any changes to the plate.

I went back to my old Slik U-210 tripod to see if there was ny way to "fool" the QR.
There isn't . It has a QR post, not a plate. It is possible to insert the QR post into the mount
without the latch in the head closing. But the camera can only be removed by pulling it straight up,
and if I try to do that, the latch snaps shut.

Morever, Slik's old post QR separates the latch funciton from the hold-down function.
You lift the lever to insert attach the camera, then rotate the lever to pull the camera
bottom snug against the tripod. At that point, it is both clamped and latched. It ain't movin'.

Also the area of contact berween camera and tripod is greater than with most plate QRs--
including the short version of Arca/Swiss.

However, what would be ideal is a QR that goes "Snap!" when you insert the plate--
so the user knows for sure that camera can't fall off the tripod. Some QRs do this,
but I haven't come across one that both latches and is truly snug.

Mechanical engineers know how to design positive-action connectors -- seat belts for
example, or the door latches on pressurized cabin aircraft (it's either latched or its really
obvious that it's not.).

Sadly, Slik still makes the #6121 post, but not the tripods that used it. Instead, in typical
industry fashion, it sells 20 different QR plates! It's almost as bad as HP inkjet cartridges.
https://slikusa.com/collections/quick-release-plates

The only reason for company to have 20 different QR plates or 200 incompatible inkjet
cartridges is to prevent competition: it splits up the market so it isn't worth another
company's while to invest capital in making an aftermarket equivalent.

These days, safety is job Number Last!

And I thought I was the one being called names.

Well I sure wouldn't lsten to anybody who shouted "Fire!" unless they did it politiely,
in a low voice. Tone is so much more important than content.

"Pardon me, I hate to interrupt, but did you notice that the building appears to be undergoing
combustion?

When you hire a servant, you can tell him how to talk. Now as to filters:

The simplest way to test for distortion is to take an exposure with a square
(e.g., Cokin system) UV filter on the lens, then rotate it 90 degrees and take
a sconnd, then slide it up or down and take a third. Then compare the
three images. I guarantee, you won't see any differnce.

The two surfaces of a filter do not have to be perfectly flat or parallel to
be free of detectable distortion. They only have to be good enough so
that the maximum angle of distortion is less than the minimum angle
the camera's sensor and given lens can resolve.

Note that two surface that are flat but not exactly parallel will not produce
distortion, because the angle of refraction is uniform. but will act as a very
thin prism. Because the angle is so small, so is the chromatic aberration.

Light is refracted when it passes from one medium to another medium
having a different refractive index: such as from air to glass. The angle
of refraction is given by Snell's Law.

You can try to measure the variations in thickness of a filter using a
dial micrometer. But chances are it will be less than the micrometer
can measure. (The only practial way to tell it's not perfectly flat
is to set it on top of a optically flat piece of glass and look for
Newton's Rings.)

More importantly, no filter ever varies in shape as much as even the
thinnest simple lens. That's why its called a "lens". It does not converge
or diverge light rays (but does scatter them a bit and absorb some--but not
as much as a lens of comperable quality-- because its much thinner).

But all you reall need to do is look out the window at a billboard
or fence, or a grid test target if you have one. Do you see any
geometric distortion? Then neither will your camera. And window
glass (mass-produced large sheets of float glass) varies in thickness far
more than even the worst photographic filter.

And when sunlight shines though a window, it does not split into its
component colors, even on a wall 20 feet away. If there is any
chromatic aberration, it is a very, very, very small amount. Now
repeat the experiment with a simple 1-element lens., projecting the
light onto a white card. You'll see the infamous "colored fringe" -- even
at a distance of just 1 foot.

The entire history of camera lens design is one long attempt to deal
with the problems caused by simple lens (especially spherical
surfaced ones). And adding corrective elements or additional
groups addes new problems. IQ problems are usually caused
by lenses, not filters.

But if you want to waste your money, there are companies that will be
happy to sell you a filter made from an optical flat.

That's a great way to never have to admit you are mistaken.

That's a good lens and a useful one. It's one of best ultra-wide zooms available
That said, I suggest you look at Nikon's published MTF data.

From the standpoint of optical correction, the best lens in any manufacture's catalog
is a long prime.

Nikkor AF-S 14-23 f2.8G:
http://www.btobey.com/nikon/images/24mm-14-mtf.jpg

Nikkor 500 mm f/5.6 PF:
http://cdn.photographylife.com/wp-content/uploads/2018/08/Nikon-500mm-f5.6-MTF-Chart-634x650.png

Those are the results of rigrous testing. What you expressed was a a personal preferrence,
not an objective fact. You may like chocolate ice cream the best--that doesn't make it
"the best food". Sorry.

In addition to aberrations, ultra-wides always introduce distoration -- seen most clearly in a fish-eye
lens --which is not measured by MTF. That won't matter is a sunset, but might m a
scene with buildings in it. You can have your choice of several different kinds of
distoration, depending on the lens design. Shoot a grid test chart, and you'll find
out which kind that lens has.

Also, any zoom has more groups (and more air-glass surfaces) than a prime.
Alse being equal (e.g., the optical coatings), the zoom will create more flare.

No matter how much money you spend for an ultra-wide zoom, the MTF isn't going to
improve much. Each class of lens has limits to performance. If you insist on an ultrawide,
you get more distortion. If you insist on a zoom, you get more aberrations. It comes down
to the buyer's priorities.

It's a good idea to try framing the scene differnt ways. But you can't do much to
change the angle of the sun except point you camera in another direction entirely.

Flare can be an interesting effect. When cinematographers and directors first started
leaving flare in moves (which didn't happen in Hollywood until the 1960s), it was
considered revolutionary. However, the novelty soon wore off.

Flare has several effects: causing visible streaking, reducing global contrast,
and blowing out highlights. Not all of these can be satisfactorily fixed.

The problem with putting bandaids on image defects is the same as with
White-Out on calligraphy: it's almost always detecdtable. It looks like what it is:
an attempt to repair a defect. Image Bondo.

This doesn't apply to global color correction. global contrast adjustment and
other processing where there is no seam and no imformation lost from the
image.

Serious landscape photographer used to limit themselves to the usual
lens filters, global contrast expansion/contraction (push/pull devleopment),
and dodging and burning: no scissors, no paste, no hand-tinting. They
worked very hard to make their dodging and burning undetectable
(and sometimes failed).

Why bother with the camera? Why not just use paint software to create
a sunset? Oh, but that would required understanding how landcapes look
in different light, and how color works.

Whether an image is great or not all depends on what you plan to do with it.
A lot of images look good on computer screens or websites that do not look
good when printed and hung in a gallery.

Perhaps our language is to blame for much of the confusion.

It uses the same word, "painter" for people who paint houses and people
who paint portaits.

And it uses the same word, "photographer", for people who make portraits
or fina art landscapes and those who shoot crime scenes or make passport
photos.

Moreover, it uses the same word "camera" for a Linhof or a Hasselblad
and for the little boxes hanging from the ceiling in stores.

Photography is not the same thing as "image capture". But perhaps in
a few years we will start calling a trail camera a "trail photographer"
and a security camera a "security photographer".

My previous post expired before I finished editing it--sorry folks.

It's just not worth arguing with people who are irrational and repeatedly
post fallacies.

Yes, it does appear that the sun moves around the earth. I do not deny that
experience. But it's bad idea to trust appearances and not try to understand
the laws of nature.

The science of optics is very relevant to the evaluation optical systems and
the diagnosis of problems.

It took me years to get to the point where I could test, adjust and repair
some camera lenses. The first piece of test equiopment that I built was
a collimator. But most of the effort was in learning the science behind
the technology--and I'm still learning.

Some questions about a car engine can be answered by a test drive. But
others require checking the timing, measuring the compression on each
cylinder, sending a sample of the drained motor oil out to a lab to check
for metals. At the very least, you have to open the hood and take a look.

Somone who thinks they can tell everything from a test drive is going to
make some used car salesman very happy.

Rather than attacking me, I wish Robert would try to find a flaw in my
argument:

1) Being flat and thin, a typical filter does not have any measurable aberrations
or distortion.

2_ Thus, it is possible to make a filter much closer to a perfect optical system
than any camera lens, whic contains thick lenes requiring additional corrective
elements. Even with correction, no camera lens is perfect.

3) Filters have a much larger aperture than any camera lens, therefore they
also have lower diffraction.

4) The optical coatings on filters can be just as good (or identical to) the coatings
on camera lenses.

5) All else being equal, a bright light outside the angle-of-view (such as the
sun,) is more likely bounce harmlessly off a flat filter than a convex lens
(becuse it will tend to strike it at a higher angle)

This is not "speculation"--it is an attempt to apply the principles of optical
engineering and accepted natural science. I do not doubt ttat some filters flare
badly---so do some lenses.

It's quite possible I am mistaken, in which case the person who can point
out my mistake will be doing me a favor.

[quote=robertjerl]I am well aware we on on one of the discussion sub-forums.
This is Bipod's post I was commenting on:

[i]Bipod (a regular here) Joined: Aug 18, 2018 Posts: 2066

Haydon wrote:
Thanks Robert for your advice. You, Larry and Amfoto, all who have used that lens in particular provide the best insight opposing an armchair photographer who has no experience with that piece of glass."
[/quote]
This is indeed a good example of the anti-scientific, anti-reason attitude that I was alluding to.

This implication is clear: no historian can know anything about the US Civil War unless he was in it,
no doctor can know anything about a disease unless he has had it.

I haven't used heroin--but I am fairly cetain it that it is addictive. And I rather value the opinion
of doctors and scientists more than that of junkies. Users are just that: users--not experts.

The word "empiricism" has two meanings: it can mean using evidence derived from experiments,
or it can mean a fool who beleives that things are always just as they appear.

As the saying goes: the plural of "anecdote" isn't "evidence".

So your test methodolgy was that you took one picture and judged it by eye?
So which aberrations does it have? What kind of distortion? What is the resolution?

So if you take a pill and feel OK, I guess you "know" the medication is safe.
Don't need any egg-head medical scientists doing a long-term, mutli-center,
reandomized, double-blind study.

A certain person who thinks like you came up with the remarkable statement that
the noise from windmills causes cancer. See, the science minded person wants to
know how sound waves who'se wavelengths is measured in centimeters or meters
can affect a single cell whose size is measured in micrometers.

I thanked them, but I was addressing only you.

What evidence or science-based argument did you post, Robert? What citation?
All I heard was anecdote and opinion.

You said you once used this lens to take some photos. Okay-dokey. That would be value
if the issue was "does it fit tightly on the lens mount?" But optical quality is hard to assess--
and it's even harder to determine what went wrong. No lens is perfect.

Moreover, what aberrations and distortions are visible depends very much on the subject of
the photograph. For example, it's very unlikely that distortion--no matter how bad-- would be
noticed in a photo of clouds or a seascape. But photograph a picket fence, and distortion
becomes obvious. (Of course, the distortion might not be the fault of the lens--it could be
perspective or in a film camera, that the film isn't being held flat.)

An image file alone isn't evidence of anything---not even of the event it depicts. We've all see
dozens of photographs allegedly of UFOs, the Loch Ness Monster, ghosts, pixies, and Elvis
alive and well and living in Vegas.

Nor court of law in the United States will accept a photograph as evidence without sworn testimony
explaning how it came to be taken and establishing a chain of custody. And criminal lawyers and
criminologists know that eyewitness testimony is often inaccurate.


Scientific facts do not dervive from from everyday experience, but from
carefully designed experiemnnts and quantitative measurements made
under controlled conditions.

It is quite diffiuclt to test a lens and draw the correct conclusions.

Being sick a lot doen't make one a doctor. Doctors learn anatomy, physiology,
biochemstry---in short, medicine.

This is ad hominem argument--a type of logical fallacy

Might I point out that this is a dicussion forum.
Discussions are much more interesting when reasons are given for opinions and beliefs.
It's even better when the reasons are reasonable.

So many UHH discussions fail to reach any sort of conclusion because only anecdote and
opnion is present, rather than reasons that can be evaluated.

His argument is that in the terms Admin states: (So his own photo work is so great he thinks Admin will steal them, so he doesn't post any?????)
[/quote]
I did not say that. Unfortunately, work does not have to be "great" to get used on
some website.

It is not theft, because you gave the Admin the right to sublicense your work.
Probably you entered into this legally binding agreement without even reading it.
[/quote]

"SUBMISSIONS

Visitor agrees as a condition of viewing, that any communication between Visitor and Website is deemed a submission. By making a submission, Visitor grants the administration and the owners of the Website a worldwide, non-exclusive, irrevocable, royalty-free, sub-licenseable and transferable license to use in any way, reproduce and distribute the submission and prepare derivative works of the submission without further permission. This includes commercial and non-commercial use of all submissions, including portions thereof, graphics contained thereon, or any of the content of the submission. Visitor agrees to only communicate that information to the Website, which it wishes to forever allow the Website to use in any manner as it sees fit. "Submissions" is also a provision of the Privacy Policy."

In the 5 years I have been on UHH I remember a few cases of other members having their photos stolen by other members but none saying Admin stole any - Did I miss any?[/quote]
More illogic. How do you know images haven't been sublicensed????

Nothing in the contract requres the Admin to notify you when and if he sublicenses your image.

Do you Robert, have a bot that checks all the world's publications and all the stock photo services
and all the webites on the Internet every day to make sure that none of your images have been used?

Where can I get such a bot? I've found both images and text from my various
websites over the year show up in Google seraches in multiple locations. If you don't
realize that internet is full of plagiarism and pirated IP, then you are even more
naive than you sound.

As I said: what you do with your image files is your business, what I do with my prints is
my business.

Good points, Bill.