Azo & 3-D effect - Urban Legend?

Photo Engineer · Jan 14, 2008

Jed;

My descriptions of 'stereo' vision with some types of eye problems are certainly illusions, but are nonetheless quite real in appearance to those who see and experience them. You can see true stereo from a single camera with one lens just by moving the camera or subject between frames. You can also see motion in stereo stills by taking subsequent frames with the subject in different positions in left and right frames. Your eyes cannot fuse this properly and the brain supplies subject motion.

I have seen stereo pairs where the subject has an arm lifted in the left (or right) frame and has their hand at their side in the other frame of a stereo pair. When viewed, the subject appears to be in motion waving the hand. This pseudo motion effect has been known since the days of early stereo pictures which took extremely long exposures with two plates. The subject moved slightly and the viewers reported seeing motion.

And, BTW, I have a venerable Kodak Stereo camera with two lenses and a level.

PE

Jed Freudenthal · Jan 14, 2008

Photo Engineer said:
Jed;

My descriptions of 'stereo' vision with some types of eye problems are certainly illusions, but are nonetheless quite real in appearance to those who see and experience them. You can see true stereo from a single camera with one lens just by moving the camera or subject between frames.

Sure, one can take pictures with a stereocamera, or one can move the camera, and take more photographs. And one can see depth.
But, I am referring to the normal situation of one picture and one lens at one position. It is like a person with one eye seeing the world. That person (and this has nothing to do with photography) can estimate distances. This ability, and every person with normal vision has that, is based on the perception of differences in hue (color/ white light), as a result of the interaction of light and the atmospheric constituents. We do that all day, but are often hardly aware of it. Because hue plays a role in this phenomenon, I can imagine that persons with certain problems with their eyes might see the world in a 'special' way. But that is nothing new.
And it makes no difference whether it is an illusion or not. I think: most interpretations of photographs we see, are illusions. At least I hope it is not an 'exact copy of the real world'.

Now, by adjusting the technique, we can take advantage of 'the ability of estimating distance' it in painting and photography. A lot has been published in the case of painting. Not much in the case of photography. But, when one understands the 'physics behind it', one can adjust the technique in photography too. However, the photographer should have a good observation skill. Technique alone is not sufficient.

Jed

Photo Engineer · Jan 14, 2008

You can certainly try to estimate differences in distance due to perspective in a photo, but depth can be added by skillful use of art. The most famous of this is the scene of Dorothy in the crossroads of the yellow brick road in which the road ended a few inches beyond her feet, but the matte painting was so skilfully done that the road seemed to continue into the distance. You could 'estimate distances clearly' there when there were none at all.

PE

gainer · Jan 14, 2008

Visual estimation or perceiption of distance in the 3D world is very different from doing it from a flat photo. A one-eyed driver in motion has a continuous change of visual angle of and between objects the rate of which is different for different distances. A motion from side to side or fore and aft of the head gives distance clues from fairly near objects. You can get distance cues from a photo with one eye by head movements, but that won't help with distances between objects in the photo. Neither for that matter will stereo vision nor change of focus, which give only information about the distance of the photo plane.

Do we have prints of the same size and scene on AZO and another paper, made with the same printing skill, so as to be able to compare them and show them to persons who do not know beforehand which is which? Can one decribe the differences that make one better than the other?

Jed Freudenthal · Jan 14, 2008

gainer said:
Visual estimation or perceiption of distance in the 3D world is very different from doing it from a flat photo. A one-eyed driver in motion has a continuous change of visual angle of and between objects the rate of which is different for different distances. A motion from side to side or fore and aft of the head gives distance clues from fairly near objects. You can get distance cues from a photo with one eye by head movements, but that won't help with distances between objects in the photo. Neither for that matter will stereo vision nor change of focus, which give only information about the distance of the photo plane.

Do we have prints of the same size and scene on AZO and another paper, made with the same printing skill, so as to be able to compare them and show them to persons who do not know beforehand which is which? Can one decribe the differences that make one better than the other?

This subject has been treated in science at length. Therefore, I rather make a reference. It was Leonardo da Vinci, who introduced the importance of estimating distance, next to the question of depth. The best way is to look into the original version or in the translation of the original version [ treatise of painting, codex urbanus latinus 1270, Princeton University Press 1956]. There are numerous modified versions.
Although it is an old text; it never lost it value. Artists used this for 500 years. Leonardo introduced the 'aerial perspective'. After this physisists (often meteorologists) have added much more information.
As you might notice from the work of Leonardo and modern scientists: there are several kinds of perspective. In a landscape, the aerial perspective is important. With a portait it might be another one.
Painters adjust their technique to the situation. For a photographer, it is not different, in my opinion. As a matter of fact: I think a photographer is even more linked to the laws of nature than a painter. And at the same time, the photographer is not willing to make a 'copy of nature'. Like the painter, the photographer want to bring his own ideas into the final print. Luckily, the photographer can play with the optical effects of 'aerial perspective' and other kinds of persecive and of the feelings radiated by the light responsible for those perspectives. It aws Susan Sontag in het book on photography who had described this controversy.

Jed

Alex Hawley · Jan 14, 2008

gainer said:
Do we have prints of the same size and scene on AZO and another paper, made with the same printing skill, so as to be able to compare them and show them to persons who do not know beforehand which is which?

Sorta, kinda. I've printed my "Barn Siding" on Azo, Slavich, and Mowrey papers. I couldn't get the Slavich print quite as good as the others for some reason. (I need to go back and look at the Slavich print again. Its been several months since I looked at it.) If I ran several prints around this crowd, most would probably be able to identify which paper was which because of the experience level here, irregardless of the 3-D effect. Maybe I could try it on one of my family members, but they would be judging the prints base on their own "pretty" factor criteria.

gainer said:
Can one describe the differences that make one better than the other?

Perhaps, but then there's also inherent tonal differences between individual papers that make it hard to describe. Also, this is primarily a visual factor, that for me, seems to exceed my verbal descriptive abilities.

gainer · Jan 14, 2008

I spent the last 20 or so years of my 30 with NACA-NASA studying simulation and human factors. It is a fact that pilots often learn to fly the simulator, whether or not it really acts like an airplane or a space vehicle. I keep thinking there must be a connection between the art of photography and the art of simulation, but I'm darned if I can see how to use one in the other. We can learn much about human factors from simulations, but not always much about the vehicle we are trying to simulate. The fact that our test piolts could fly either one equally well only tells you how good the pilots were. Their greatest contribution is often their verbal description of how the simulator fails in truly simulating what it was meant to simulate. One of our test pilots took off one day in a test plane in which the elevator controls had been reversed by mistake. He very quickly learned how to control it well enough to land safely. He had no trouble remembering how to change his pants!

We have seen photographs we consider to be great by people who never used AZO. Maybe they would have loved it if they had.

Alex Hawley · Jan 14, 2008

Ahhh, Patrick, I think you may have touched upon a key point. The really good pilots are those who thoroughly understand what they are doing; they have the ability to continually synthesize in their mind what is going on. Thus when an anomaly occurs, they quickly understand it, know how to compensate for it, and get safely out of the situation. Such a situation would be lethal, almost instantly , for a less capable person. These are the ones who are continually operating with their heads, not doing it by rote. Same goes with anyone who successfully operates a high performance machine, say like a race car driver.

Anyone can take photographs by rote. That has been the goal of the technology ever since George Eastman. Lots of people can fly an airplane by rote. An extreme few can live to tell about doing it with control surfaces reversed.

So it is making photographs with this 3-D effect I believe. As for myself, I don't plan it that way. If I get it, I get; if I don't I don't. I'm just starting to understand what is going on so maybe I can start achieving it more often.

What an excellent, thought-provoking thread!

gainer · Jan 15, 2008

I guess we could safely say that while the best tools and materials make it easier to show ones talent, poor ones will not keep it from showing. Cavemen showed us that much. The art is the driving force for design of those tools and materials, not the other way around, though there is resonant feedback in the circuit.

Jed Freudenthal · Jan 15, 2008

gainer said:
I spent the last 20 or so years of my 30 with NACA-NASA studying simulation and human factors. It is a fact that pilots often learn to fly the simulator, whether or not it really acts like an airplane or a space vehicle. I keep thinking there must be a connection between the art of photography and the art of simulation, but I'm darned if I can see how to use one in the other. We can learn much about human factors from simulations, but not always much about the vehicle we are trying to simulate. The fact that our test piolts could fly either one equally well only tells you how good the pilots were. Their greatest contribution is often their verbal description of how the simulator fails in truly simulating what it was meant to simulate. One of our test pilots took off one day in a test plane in which the elevator controls had been reversed by mistake. He very quickly learned how to control it well enough to land safely. He had no trouble remembering how to change his pants!

I discussed the matter with the director of a similar institute, but for military aviation. I discussed it with physicists with civil applications in mind. My daughter developed a system with photographic images for use with minmal invasive surgery.
The general idea is that this is not applicable in art, without mentioning the reason. I think that the reason is that a pilot, surgeon etc. should not work with illusions, but a reality.
For an artist (and photographer), illusions are important. E.H. Gombrich has spent a book on the subject: ' Art & Illusion'.
And , to repeat Leonardo: 'One has to understand the world around us first'. Then the artist can give his view on the world, assuming he has sufficient skills (chiaroscuro).
There are many different kinds of photography. But in the photography direction, which you might call art, the situation is not different. As a matter of fact, Leonardo used the camera, without film, too. The manual written by Leonardo is to teach 'how the world around us is constructed'. Much is, in fact, physics.

Jed

Michel Hardy-Vallée · Jan 15, 2008

gainer;573104I keep thinking there must be a connection between the art of photography and the art of simulation said:
Ahhh, you must be thinking about something like this book:
http://www.hup.harvard.edu/catalog/WALMIM.html

It's influential, and while the argument can over-reach, it applies to many situations.

matti · Jan 15, 2008

I was thinking today that edge effects must have a sweet spot magnification. Maybe that also applies to resolution and grain and has something to do with the 3d-effect. Anyone have any ideas on this? If I remember correctly Barry Thornton argued that larger grain sometimes looks "sharper".
/matti

Photo Engineer · Jan 15, 2008

Matti;

Edge effects vary with magnification as does contrast. I have posted portions of Mike Kriss' 60 page paper on it here on APUG. The smaller the edge basically, the higher the contrast and so there is micro and macro contrast involved with just about every negative. This, of course, varies with developer and method, but only applies to film. Paper is another story.

PE

Photo Engineer · Jan 15, 2008

I just reposted the Kriss data in another thread for a similar question to yours Matti.

(there was a url link here which no longer exists)

PE

Photo Engineer · Jan 15, 2008

I've been revisiting this 3D effect over and over in my mind trying to remember something from the past, and suddenly with the Kriss data it clicked.

When you look at an enlargement of a MF or 35mm negative, you are looking at the micro-contrast of the negative for the most part. This micro contrast is in tune with the edge effects.

When you look at a contact print of a LF or ULF negative, you are seeing the macro and micro contrasts at the same time in one print as well as the edge effects. The result of this is that you see the image at different visual contrasts depending on size. Small things are at higher contrast than large things in a contact print while they are all at the same contrast (for all practical purposes) in an enlargement.

Does this seem like a logical explanation for some of the differences between enlargements and contact prints? It does to me.

PE

matti · Jan 15, 2008

Thank you. Interesting. But does the difference in line width come from different developer of different "line width" of the subject matter? (I am a bit slow here.)

/matti

Photo Engineer said:
I just reposted the Kriss data in another thread for a similar question to yours Matti.

(there was a url link here which no longer exists)

PE

Photo Engineer · Jan 15, 2008

Matti;

The line width is due to the size of the slit used. The density of the line on an absolute basis is due to exposure, and the edges on each line is due to the emulsion, developer and agitation. The macro and micro contrasts are a measure of density at each exposure at 1 given slit width at a time. This is only true in a film. The edge effects in paper may be assumed to be nonexistant.

PE

Jed Freudenthal · Jan 15, 2008

Photo Engineer said:
I've been revisiting this 3D effect over and over in my mind trying to remember something from the past, and suddenly with the Kriss data it clicked.

When you look at an enlargement of a MF or 35mm negative, you are looking at the micro-contrast of the negative for the most part. This micro contrast is in tune with the edge effects.

When you look at a contact print of a LF or ULF negative, you are seeing the macro and micro contrasts at the same time in one print as well as the edge effects. The result of this is that you see the image at different visual contrasts depending on size. Small things are at higher contrast than large things in a contact print while they are all at the same contrast (for all practical purposes) in an enlargement.

Does this seem like a logical explanation for some of the differences between enlargements and contact prints? It does to me.

PE

I think, you just hit an important point. I did not want to go in this detail before. One can observe macro and micro contrasts at the same time. And with certain modern lenses they show up. And, think about the implications for the final print. There is a difference between a contact and an enlargment. But, this is just the starting point. There is much more to it.

Jed

gainer · Jan 15, 2008

The eye has its own edge effects which can be seen when looking directly at sharp edged objects in the right lighting. The photographic chemical edge effects can be fairly constant in absolute dimension from 35 mm on up, but the perceived edge effects will be objectively greater in an enlarged print from 35 mm than in a contact print from 8X10. The edge effects in the contact print will probably look more like those perceived in the original scene, while those from the enlarged 35 mm will be exaggerated.

Photo Engineer · Jan 15, 2008

gainer said:
The eye has its own edge effects which can be seen when looking directly at sharp edged objects in the right lighting. The photographic chemical edge effects can be fairly constant in absolute dimension from 35 mm on up, but the perceived edge effects will be objectively greater in an enlarged print from 35 mm than in a contact print from 8X10. The edge effects in the contact print will probably look more like those perceived in the original scene, while those from the enlarged 35 mm will be exaggerated.

Patrick;

Look at the line traces from Kriss. You will note that as the size decreases, the edge effect goes down while contrast goes up. This is what you see with 35mm. Effectively the average object size in the negative becomes smaller and edges become less pronounced while the contrast between objects increases.

Of course, you can change the development condition to increase edges of smaller objects, but this is altering the test and therefore must be applied to contact prints of 8x10 negatives.

Therefore, although the eye does have an 'edge' effect between light and dark objects and it varies with intensity and wavelength, this is going to be part of every print at every size. All else being held constant, the edge effects in the negative will predominate.

PE

gainer · Jan 16, 2008

I thought we were talking about prints of the same size from negatives of different size, both of the same subject. Is not your last paragraph what I said? The truest negative would have no chemical edge effects and would have been exposed by a perfect lens. Then the eye could see the edge effects it would see in the original subject. The problem is with trying to increase edge effects in the belief that it will make the 35 mm photo look like one made with an 8X10.

Jed Freudenthal · Jan 16, 2008

gainer said:
I thought we were talking about prints of the same size from negatives of different size, both of the same subject. Is not your last paragraph what I said? The truest negative would have no chemical edge effects and would have been exposed by a perfect lens. Then the eye could see the edge effects it would see in the original subject. The problem is with trying to increase edge effects in the belief that it will make the 35 mm photo look like one made with an 8X10.

Gadsget: we are talking on prints of different size from a negative of the same size. The description has been somewhere back in this thread. The observations from looking at the different prints have implications for the conclusions.

Jed

Jed Freudenthal · Jan 16, 2008

Photo Engineer said:
Patrick;

Of course, you can change the development condition to increase edges of smaller objects, but this is altering the test and therefore must be applied to contact prints of 8x10 negatives.

Therefore, although the eye does have an 'edge' effect between light and dark objects and it varies with intensity and wavelength, this is going to be part of every print at every size. All else being held constant, the edge effects in the negative will predominate.

PE

This is absolutely right. My conclusion in the past was therefore: get rid of the edge effects, by adapting the film development conditions. And that is what I did. And the image quality of final prints was what I had predicted on theoretical grounds.

Jed

Kirk Keyes · Jan 16, 2008

Jed Freudenthal said:
My conclusion in the past was therefore: get rid of the edge effects, by adapting the film development conditions. And that is what I did.

Jed, how did you do that? Rotary processing or continuous agitation? How can you be on APUG and not be a believer in any of the multitudes of stand, semistand or whatever the latest variation of minimal agitation techniques are called?

While I'm not sure you can completely get rid of all edge effects, you certainly can do things to minimize the formation of them.

gainer · Jan 16, 2008

The trouble I have with the Criss data is that only a single line is used. A very different result can be obtained when a picket fence type of target is used. A fence of 10 micron lines separated by 10 micron spaces at the film plane would only show a blur with most lenses we can afford. There are not only edge effects but adjacency effects, some optical and others chemical.

Anyway, I find that perspective is important to the feeling of depth. The viewpoint for seeing the scene in proper perspective through the print is a function of focal length of the camera lens, size of the negative, and magnification between negative and print. Ultimately, one should be able to find a viewing distance where the feeling of depth is maximized. We can't hang it all on resolution and/or contrast, or there would be few works of great painters that gave a feeling of depth.

Azo & 3-D effect - Urban Legend?

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