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Archive 2012 · Pink Hyancith
  
 
Bob Jarman
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p.2 #1 · p.2 #1 · Pink Hyancith


Admitting I have not done a thorough read, does the f/11- diffraction behavior apply to lenses not designed for digital? I interpreted Greg's as a non-digital, manual focus Nikkor, one of which I gave to my daughter several years ago.

Bob



Feb 24, 2012 at 02:31 PM
gregfountain
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p.2 #2 · p.2 #2 · Pink Hyancith


Bob Jarman wrote:
Admitting I have not done a thorough read, does the f/11- diffraction behavior apply to lenses not designed for digital? I interpreted Greg's as a non-digital, manual focus Nikkor, one of which I gave to my daughter several years ago.

Bob


That's a good question Bob! I would guess that the quality of the glass also plays a part on how the light is resolved, in addition to how much the light is "squeezed" though the diaphragm.. But in defense of the Nikkor AiS lens I used, I find it resolves better than much of the AF glass in my kit! I have three of the AiS lenses and being perfectly honest, I would use none of them handheld, as I just don't have the skill to hold still long enough to get them focused properly, but on a tripod, I believe the results are hard to beat unless you move into the Leica realm.....

Greg



Feb 24, 2012 at 02:35 PM
cgardner
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p.2 #3 · p.2 #3 · Pink Hyancith


Because human perception is so subjective, and because there are so many other reproduction variables affecting IQ, in most cases you will not notice diffraction unless you shoot the same fine textured object at the same distance with different apertures and compare.

If you do take the time and trouble to compare you will see some difference. On test shots of resolution charts most lenses have optimal optical resolution about 2-3 f/stops smaller than wide open. So if you have an f/2.8 less it will sharpest optically in the 5.6 to 8 range. As physical aperture size gets smaller the diffraction progressively degrades resolution.

After validating and accepting the fact there is a difference it then becomes a conscious decision of whether the added DOF gained by shooting at smaller apertures is worth the loss in resolution. The best way to judge that I to bracket aperture then sort it out on the computer where you can see the differences by side-by-side comparison.

Camera gear is marketed on the basis of technical perfection rendering every pixel in the frame tack sharp and evenly exposed. But perceptually in a photograph having the edges of the frame a bit less sharp and darker is actually very effective because it makes what is sharper and brighter in the middle contrast by comparison, pulling the attention of the viewer here.

Most of the edits I do as part of C&C usually involve some degree of subliminal level blurring and darkening of the edges of the frame and other distracting areas to "push" the viewer to the sharper, brighter, more important content that tells the story.

It was said a well-known cinematographer could "light a set with just a bucket of black paint". That's pretty much true of portrait lighting. If you put a person in dark clothing on a dark background the viewer will find the face regardless of how it is lit they might not find it flattering, but they will find it.

But say you photograph a black dog on a black background, or a bug on a leaf. Because the dog and bug aren't wearing clothes there's nothing to artificially create the lighter area on the face to attract attention. So in the photo of dog and bug its more difficult for the viewer's brain to make heads or tails out of what they are looking at because there are no contrast gradient clues.

That's where sharpness and DOF come into play. If you use shallow DOF and make the head of the dog or bug sharp and the body blurred, tonal contrast being equal everywhere the viewer's brain will send the eyes to the area of greater sharpness. With a subject like a black dog you can also create that illusion of sharpness by using a direct accent light on the head to create more specular highlights, and the illusion of texture in the fur there.

For something like a reclining human nude the parts of the body which contrast with the tone of the background the most and are the most sharply focused will get the most attention. The distance of the various body parts to the key light and fill to create the contrast gradient, and their distance to the camera lens to create the DOF gradient create the "roadmap" for the viewer to follow along the body to whatever parts you want to feature.

The point is not to get too hung up on the technical stuff to the point of losing sight of the broader goals of the exercise which is creating an eye path across the content in the frame that tells a story by leading the viewer over any needed context to a focal point where the "Ah ha!" moment of recognition of what the photo is about occurs.

In a shot like this flower its more a matter of leading the eye to one pre-determined spot and making the trip to get there varied and thus more interesting...

With gradient of contrasting sharpness....
http://super.nova.org/EDITS/FlowerSharp.jpg
and gradient of tone and color saturation..
http://super.nova.org/EDITS/FlowerSharpDark.jpg

In the original the small flower down near the bottom is the brightest one in the frame the star in the spotlight. In my edit it is hidden in the shadows and the flower at the top put in the spotlight.

It's worth noting exercising that degree of pre-visualization and control at capture with the lighting is easy to do with flash which can be aimed. It can also be done with ambient using flags, scrims, mirror or foil covered cards, etc.





Feb 24, 2012 at 02:46 PM
RustyBug
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p.2 #4 · p.2 #4 · Pink Hyancith


Diffraction is a property of the trignometry involved with the angle at which the light is being 'fracted". Not sure of its origins, but I think of diffraction as a word that means "diffusion" caused by "fraction" i.e. diff + fraction = diffraction. Fraction referring to a fracturing or dismantling/dispersion/portion of something that was once whole.

In the case of photons, the change in angle requires the light to be spread farther apart which both reduces the density of photons and the angle of incidence. From a trignometry/physics perpsective, that means the photon is now striking the sensor (or film) with less energy (glancing blow) than if the light path were to remain perfectly straight/perpendicular. While we can compensate for the density/volume of photons reaching the sensor by allowing the shutter to remain open longer, we are not changing the angle of impingement that the photons are striking with ... i.e. "direct hit" vs. "just grazed him".

Light is a vector quantity. Most of us realize that AI=AR (Angle of Incidence = Angle of Reflection). Change the angle that light is striking, and you change the amount that if being reflected. However, the unmentioned corollary to that is ... change the angle of the light striking, and you change the amount that is being ABSORBED.

All surfaces exhibit some degree of reflectance and absorption. A surface that absorbs 99% of the light energy (i.e. black) only reflects 1% of that energy that is striking it. With more of the light entering at angles that create less absorption and more reflection, the amount of absorption is reduced. The remaining amount that is reflected, most of that light gets captured by the black internal components of the camera. That helps keep it from 'bouncing around' too much. But that still doesn't do anything to improve the LESS absorption aspect that is caused by the more oblique angles. When we are using apertures that induce diffraction, having a straighter incoming light path (think spot/grid) can help mitigate the effect of diffraction (as a trigonometric function).

From that it is simply that the more direct the light hits the sensor, the more absorption that occurs. In lighting, in general, we know that a soft box or umbrella disperses and changes the angles to much more obtuse ones, whereas a grid of a spot changes those angles to more direct angles. You can get a properly exposed image using either one, but the level of contrast will be significantly different. It is the same with light striking your sensor/film, as it is with it striking your subject.

Simply put ... light is light.

Whether you are shooting on film or digital, the change in angles caused by your choice of aperture remains to have the same effect on the projection. There might be a difference in refelctance/absorption between film vs. digital, but the light that you are SENDING to it remains the same. Adjusting the aperture, impacts the angle of the light path ... and I simply sum it up like this:

Straighter light = more absorption & more direct reflection = more contrast. Diff - fracted light = less absorption & more reflected away = less contrast.
(This is readily seen by simply changing the beam pattern of a flashlight as you shine it on an object from a constant position.)

Light is light, whether on the subject, through the lens or in the camera. And while most people will NEVER go throught the physics & trigonometry involved, this is a VERY LOOSE explanation of how/why diffraction is involved and one would have to know the distance between the aperture and the next element, as well as the shape of the next element to know which aperture is optimal by design to generate the least amount of loss. Suffice to say that whether it is 5.6 or 2-3 stops down from WO (fairly typical) ... the FARTHER you move away from the optimal aperture, the greater its effect.

Long, OT and a hodge-podge of science/analogy, but hopefully it helps more than it confuses.

BTW ... my physics instuctor was the co-inventor of night vision for the Pentagon ... suffice to say light was his thing.



Edited on Feb 24, 2012 at 06:22 PM · View previous versions



Feb 24, 2012 at 03:59 PM
gregfountain
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p.2 #5 · p.2 #5 · Pink Hyancith


Thanks for taking the time Chuck. I appreciate the effort, but two things stand out in your edits. One, the blurring effect you used destroys my efforts to produce an overall sharp image. Two, I absolutely detest coordinated frames!

In all honesty, the small bloom doesn't bother me, but I see your point. I think I would approach that a little differently and perhaps burn it down a little to lessen the distraction without losing the detail in the leaves that for me, are a major feature of the upward flow of the composition. The blurring kind of eliminates that effect.

I didn't mean to suggest that I'm against using flash. In fact, the vast majority of my images are produced using artificial light in one form or another. That said, I much prefer natural light when and where I can utilize it.

Greg



Edited on Feb 24, 2012 at 04:07 PM · View previous versions



Feb 24, 2012 at 04:01 PM
gregfountain
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p.2 #6 · p.2 #6 · Pink Hyancith


Kent. Huh? You have a far better understanding of the physics involved with photography than I would guess 99% of the photographers out there! I'm trying to gain more understanding of the technical side of photography, so bear with me!

Greg



Feb 24, 2012 at 04:05 PM
RustyBug
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p.2 #7 · p.2 #7 · Pink Hyancith


No worries ... all you need to remember is this:

Straight light packs more punch.
(S&P to taste)

Yeah, I went to school to learn that.



Feb 24, 2012 at 04:08 PM
dmacmillan
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p.2 #8 · p.2 #8 · Pink Hyancith


RustyBug wrote:
Long, OT and a hodge-podge of science/analogy, but hopefully it helps more than it confuses.
BTW ... my physics instuctor was the co-inventor of night vision for the Pentagon ... suffice to say light was his thing.

References please. Very little of what you said is anything like the theory and nature of light and optics I was taught in physics.
For instance, the discussion of light "glancing" off the sensor or hitting it straight confused me. The light that hits the sensor is collected and focused by the lens, how can the direction of the light change?

How does any of this relate to the photo up for consideration? How could the photographer put any of this to any practical use?


Edited on Feb 24, 2012 at 04:21 PM · View previous versions



Feb 24, 2012 at 04:19 PM
cgardner
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p.2 #9 · p.2 #9 · Pink Hyancith


gregfountain wrote:
Thanks for taking the time Chuck. I appreciate the effort, but two things stand out in your edits. One, the blurring effect you used destroys my efforts to produce an overall sharp image. Two, I absolutely detest coordinated frames!


No problem on either point. Baskin-Robbins sells 32 flavors of ice cream for the same reason tastes vary.

My point was simply that the goal creating a uniformly sharply focused image, a technically driven one, usually doesn't produce one which is as enjoyable to look at as one where contrast gradients guide the eye.

FWIW I find looking at dark photos surround by white borders very distracting when presented on a dark page background like FM and make very little sense on a cause and effect basis perceptually. It's like driving at night and being blinded by the high beams of an oncoming car. The white borders make more sense perceptually on a white page or wall where they recede into the larger negative space of the wall and make the content contrast with that larger negative space. That is after all the point of adding a mat, to increase the negative space and pull / push the view from edges to center of photo.



Feb 24, 2012 at 04:19 PM
gregfountain
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p.2 #10 · p.2 #10 · Pink Hyancith


cgardner wrote:
No problem on either point. Baskin-Robbins sells 32 flavors of ice cream for the same reason tastes vary.

My point was simply that the goal creating a uniformly sharply focused image, a technically driven one, usually doesn't produce one which is as enjoyable to look at as one where contrast gradients guide the eye.

FWIW I find looking at dark photos surround by white borders very distracting when presented on a dark page background like FM and make very little sense on a cause and effect basis perceptually. It's like driving at night and being blinded by the high
...Show more

No problem squared! my thing with the frames stems from viewing someone else's posts, from long ago, who in my opinion, misused the concept to a degree that I stopped looking at his work, and i became determined my work would never resemble his.



Feb 24, 2012 at 05:03 PM
 

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dmacmillan
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p.2 #11 · p.2 #11 · Pink Hyancith


I like your final version. It looks very nice. Experimentation is good.

I found some of my negatives had more range than I could capture in one pass. I tried multiple scans and a type of exposure stacking that allowed me to get what I was after.



Feb 24, 2012 at 05:19 PM
RustyBug
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p.2 #12 · p.2 #12 · Pink Hyancith


Dmac ... the amount of energy that is transferred to the film or sensor is responsible for the conversion of light energy into either the electrical signal or chemical change in the emulsion.

This is a vector force. Vector forces are subject to trigonometric functions. Diffraction changes the angle of impingment. Angle changes are trig changes and correspondingly reduce the force applied @ AI. This is the reason that sensor technology incoporates microlenses, in an effort to refract the oblique light to a more direct impingement of the sensor. More direct vs. more oblique is preferrable for the greatest transmission of force. Ideally, a sensor would not lie in a flat plane, but be curved in order to receive the maximum energy from a perpendicular impingement at all points ... but I digress.

BTW ... no references ... I just made it up.
You know, that whole vector quantity thing.

Wikipedia shows a couple of formulas @ diffaction. One is relative to the airy disc computation, the other @ sin of theta. Deeper research on the matter will reveal the continued trig function ... but you'll have to do that on your own. This is why sharpness (airy disc overlap) and contrast (applied energy @ vector force) are related by the effects of diffraction. Two different issues but we speak of them as one.

Edited on Feb 24, 2012 at 06:42 PM · View previous versions



Feb 24, 2012 at 05:25 PM
gregfountain
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p.2 #13 · p.2 #13 · Pink Hyancith


Mt head hurts. Anyone got some Tylenol?


Feb 24, 2012 at 05:28 PM
gregfountain
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p.2 #14 · p.2 #14 · Pink Hyancith


My head hurts. Anyone got some Tylenol?


Feb 24, 2012 at 05:28 PM
cgardner
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p.2 #15 · p.2 #15 · Pink Hyancith


My head hurts so bad I'm seeing double


Feb 24, 2012 at 07:05 PM
Bob Jarman
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p.2 #16 · p.2 #16 · Pink Hyancith


To infinity, and beyond!


Feb 24, 2012 at 08:18 PM
cgardner
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p.2 #17 · p.2 #17 · Pink Hyancith


I stay at hyperfocal distance nowadays.

When you venture beyond infinity, its often difficult to find your way back.

The 70's taught me that



Feb 24, 2012 at 08:25 PM
AuntiPode
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p.2 #18 · p.2 #18 · Pink Hyancith


Diffraction is a result of the wave behavior of light. Hopefully, this site's explanation will make sense:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm



Feb 24, 2012 at 08:57 PM
RustyBug
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p.2 #19 · p.2 #19 · Pink Hyancith


AuntiPode wrote:
Diffraction is a result of the wave behavior of light. Hopefully, this site's explanation will make sense:

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm


+1 ... see page 1



Feb 24, 2012 at 10:28 PM
lylejk
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p.2 #20 · p.2 #20 · Pink Hyancith


Three edits for you. The first one's the serious edit; just felt it needed a little brightness and vibrance (my taste; many here have different tastes of course). The second edit it some artistic descretion. Added some glow if you will. The third result's just pure play since I wanted to.



http://img585.imageshack.us/img585/9827/626195.jpg

http://img191.imageshack.us/img191/6414/softglow.jpg

http://img804.imageshack.us/img804/8929/bizaar.jpg



Feb 25, 2012 at 01:59 AM
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