Seeing the Unseen

This week I would like to celebrate the amazing capability of modern photography to help us to see the unseen.  My goal is only to touch on what is possible and to provide links to more detailed explorations.

From its invention, photography has been a medium that was prized for its ability to capture what we see in flawless detail, freezing more of "reality" than could ever be absorbed by our limited visual perceptions.  Without special forethought, my photography has tended toward images that celebrate the beautiful detail of the natural world.  I have tried to use the remarkable powers of digital photography and editing to place viewers in locations as I have seen them, working to display the mood as well as the reality of the remarkable world around us.  But photography has always provided a means to see things beyond our normal perceptual capacity, that are not accessible to the naked eye (THERE, I got the word "naked" into the article - TWICE!  Watch my hits soar!). 


Anyway, In the beginning photography captured "Reality" in its own way based on its technical limitations.  It has always had the remarkable ability to freeze time, not only for moments but for centuries.  As initially a black and white medium, photography washed the color from the world and forced a new focus on light and pattern that had always been hidden under a gaudy chromatic layer in our perception.  Photography has expanded and altered our vision in many other ways and, digital photography, although not required for many of these advances, has made them more easily accessible and pushed opened the door to these unseen new worlds.  I have discussed many of these techniques in much greater detail in previous articles, but here is a brief list of some of the ways that photography can open our eyes to a new worlds.  Let the journey begin.  




Infrared
Infrared photography is perhaps the best example of seeing the unseen.  Infrared is the portion of the electromagnetic spectrum beyond deep red.  Although these longer wave lengths are beyond the ability of our eyes to detect, infrared photographs have been captured since the early 1900's.  Today a digital camera can be modified to respond to the infrared making it much easier to capture this invisible world.  The infrared spectrum shows foliage in brilliant light, making summer scenes appear like winter landscapes.  It cuts through haze and reveals puffy clouds in stark contrast against inky black skies.  With infrared photography it is often possible to capture powerful images on days when the light is too flat and dull for strong conventional images.  I found it well worth the expense to modify my old Canon 20D doorstop to become my IR camera.
For More Information:
 Infrared, Seeing Photography in a Different Light


HDR
High dynamic range photography can be used to overcome the 

Improving Dynamic Range

limitations of film and digital sensors in recording the full range of light and dark apparent to our eyes.  In this sense it actually improves the ability to capture what we can already perceive, but HDR and its evil twin, tone mapping, has the seemingly unbounded artistic capability to mutate reality, 
turning a mirror on the artists mood and fancy rather than the reality of the moment.  I love HDR because it provides such an unlimited opportunity for self-expression.  I generally use these tools to render images that better reflect the dynamic range that was apparent in the field, but occasionally it is fun to go crazy, jump through the looking glass,  and produce something that truly would never be apparent to the eye.




Going Crazy

For More Information:
HDR: Bon Appetitt
Taming the HDR Beast



Stop Motion:
Stopping motion requires fast shutter speeds that the high ISO capability of new digital cameras has made more practical.  I remember, from the ancient past, when loading the camera with  ASA 400 film was a considered reckless, trading speed for the assumed damage to image quality.  Based on the lighting, I can now easily dial up the ISO to whatever is required, to allow a shutter speed fast enough to freeze the action or capture images in inky darkness..  The combination of the improved low light sensitivity of new digital sensors and the capability of software noise reduction algorithms has made it possible to maintain acceptable image quality at ridiculously high ISO levels.
For More Information:
 Accidental Bird Photography
Great Blue Heron on Harvey Pond


Long Exposure;
Long exposures have always been a capability of photography.  In 

Crowded Portland Street

fact in the early days it was a requirement. Daguerreotype portraits required an exposure of 2 or more seconds. Today long exposures can accomplish a long list of magical effects.  An exposure of a even a second or less can transform a roaring chaotic stream into a soft dream-like confection, looking nothing like the original scene, but providing a sense of frozen movement.  Long exposures of a busy street can remove all the distractions of moving cars and annoying people,  magically focusing on the stationary scene.  Star tract images of the night sky transforms individual stars from points of light into majestic arcs rotating around the north star. All of these technique are made much simpler by the ability, in the digital camera, to immediately review the results and adjust exposures accordingly

For More Information:
Photographing the Magic of Velvet Water
Long Exposure Crowd Control
Star Track Photography


Deep Space:
While we are talking about night sky images, I think one of the most impressive ways that digital cameras have altered our sense of nighttime wonder has come from the ability that long exposures and high ISO have to extend our vision into deep space. ISOs ranging from 1600 to 6400 and exposures of 20-30 seconds brings a dense sea of stars into view that are invisible to our eyes even on the darkest night.  Beyond doubt,  the celebrity of this celestial show is our own galaxy, the Milky Way.  The most impressive images usually show the Milky Way's brilliant band in some appropriately interesting setting, and there are now many programs and Apps that can tell us precisely when, and where to stand to place a lighthouse, a tree or a silo in front of the show.  I live in the country and I often get a clear view of the sky, but even here the digital camera easily converts a subtle smug into a breathtaking view of our galactic disc.
For More Information
Night Time Photography, Searching for the Milky Way
Photographing Comet PanSTARRS


Time Lapse
Time lapse photography compresses time allowing us to see in a few seconds what occurred over hours.  All that is necessary is a sturdy tripod, an intervalometer to time the exposures and software to assemble the hundreds of images into a video.  For quick and simple time lapse videos I have used Quick Time, but many other options exist. I'm still a novice, but I have enjoyed creating videos of the setting sun, billowing clouds,  or stars moving majestically across the sky.  I even have one of Susan and I decorating the Christmas tree. 

Monadnock Sunset



 
Tree Trimming


For More Information
Time Lapse Time


Focus Stacking
It may seem that the use of focus stacking to achieve a deep depth of field only replicates what our eyes can capture, but in fact eyes have the same focusing  limitations as any lens and iris system.  The only reason that we feel we can see everything from near to far in sharp focus is that our eyes are constantly and subconsciously adjusting focus as we move our attention around the scene.  A photograph with sharp focus throughout is actually a representation of the world beyond the capability of our vision, but it does match the dynamic nature of our perception.
For More Information:
Focus I
Focus II
Hand-Held Focus Stacking


Of course there are more ways that digital photography allows us to see the unseen. Editing software can alter our vision and a world without a tangle of wires in front of every beautiful scene is a priceless gift of Photoshop. It has been thrilling to explore some of the photographic options available, but It is also humbling to realize all that I need to learn.  But then again the endless opportunities to learn are what make photography endlessly exciting.

Jeffrey Newcomer
Partridgebrookreflections.com

Read More

Hand-Held Focus Stacking

Snow Peak, Mount Monadnock, Marlborough, NH

Using Auto-Focus Points to Hold the Frame

This week I wanted to share a simple technique to obtain multiple (or at least two) images for focus stacking while hand-holding the camera.


Focus Stacking
I have previously discuss in considerable detail the technique of focus stacking to achieve deep depth of field.  This approach
requires multiple images focused at different planes of the scene which are then combined in post processing to achieve sharpness throughout.  A key requirement of the technique is that the images all be framed to match when aligned in the computer.  With sophisticated software, such as Photoshop, the match does not have to be perfect, but typically this is best achieved with the camera locked down on a tripod.  It can be quite challenging to manually vary focus while trying to hand-hold the framing perfectly constant.  This is where my camera's auto focus points can come to the rescue.

I have never been a big fan of auto-focus for my landscape

Hibernation, Pomfret, Vt.  Two focus planes.

photography.  Even as the technology has improved, I tend to prefer to assure sharpness by manually focusing, often on a tripod and, in poor light frequently, using the Live View Screen.  But when I am faced with a scene which contains a discrete foreground and distant background,  I can often get good results with a two image stack, one focused on the foreground detail and the other on the background.  This is the situation where auto-focus can save me the chore of getting out my tripod, if I have it on hand.


Mount Monadnock
Most photographers are familiar with the technique of holding the shutter down half-way to lock focus on a part of the scene and then recomposing for the final shot.  This is most frequently used when focusing a subject that is off center, but the same technique can be used to grab a couple of images for a simple focus stack.  In the example of Mount Monadnock shot from Marlborough, New Hampshire, I locked focus on the detail of the fence and then re framed to include the distant mountain.  The first image caught the fence in clear focus and then without moving the camera I locked focus on mighty Monadnock and shot again.  As I shot the first image I carefully noted the position of the central focus point square to assist in close alignment of the second image.  In more complicated situations, fully sharp focus stacking can require more than two images, but in bright light, when I can stop down, two are often enough to get good results, especially when there are just two discrete planes of interest. 

Canon 5D Mark II Focus points

Mill Ice, Harrisville, New Hampshire
My Canon 5D Mark II has 9 focus points displayed on the screen, but only the central square is a cross sensor, vertical and horizontal, and therefore the most accurate.  When possible I try to use the central point for focus stacking but there are many times when the central point aligns with neither the foreground or background in my desired composition.  Faced with this situation I can usually find one of the other focus points that will provide the coverage I need.  In my image of the frozen mill pond in Harrisville, New Hampshire, I angled the camera down to using the top focus point to lock in the sharpness of the foreground ice and then recomposed.  In my second image, the focus point was in perfect position to catch the iconic Harrisville Public Library. 

Mill Freeze

Using one of the 8 peripheral focus points can reduce the reliability of the auto-focus, especially in dim light or low contrast. To help, I have switched my focus lock from the shutter to a button on the back of the camera that doesn't require continuous pressure to maintain the focus.  In the mill pond image, I could lock the foreground focus with the central point and then switch to the upper point ready for when I refocused on the background.  Not all cameras can switch the focus button. The directions for mine were buried in an obscure corner of my manual, but, with practice, the ability to lock focus without having to hold the shutter down, works well for me in most situations.

Focus Button on Back of the Camera

Ashuelot River, Keene, NH,
Multiple Focus Planes

The trick with this technique is to hold the camera steady as you re-press the shutter and to learn how to move the focus point around the screen.  I have gotten good enough that I will occasionally try to move the focus point within the screen to catch more than just two images for stacking.  The more manipulations I try, the harder it is to maintain the frame, but Photoshop can do some amazing things with auto-alignment.  Still it is about at this time that I grab for the tripod.




The speed and accuracy of auto-focus in modern cameras is amazing and improving all the time.  I still like to use manual focus in many landscape situation but it is important to understand your camera's focusing capabilities and to use them when the time is right.

Jeffrey Newcomer
partridgebrookreflections.com

Read More

Diffraction & Best Lens Sharpness

As a landscape photographer, I am frequently striving to capture the maximum depth of field possible, but as is true of all photography, compromises need to be made on the path to the sharpest images.  The widest DOF is obtained at high f stops (small apertures), but with ever smaller apertures diffraction begins to affect sharpness, making images progressively softer.

Yikes, Physics

http://innovativescience.blogspot.com/2011/02/diffraction.html

Diffraction is a property of light related to its behavior as a wave.  Light passing through a lens does not focus sharply to a point, but spreads out as it is bent around the hard edges of the iris. The result is a soft bull’s eye, which is called the “Airy disk” and results in a softening of the detail in an image.  The name “Airy disk” may seem remarkably fanciful, especially originating from optical

Airey Disk:Wikipedia

engineers, but it does not come from its soft airy appearance.  The fact is that the guy who discovered the disk was named “George Airy”.  Diffraction is an innate property of light and not a defect in the lens.  It is present in even the most precisely constructed and expensive lens and grows worse as the aperture becomes smaller.  A few weeks ago I demonstrated the star burst effect created by diffraction on Christmas lights when small apertures are used.  The effect is minimal when the lens is wide open, but other optical defects such as spherical aberration, diminished sharpness at large apertures.  The balance of these competing effects means that the sharpest f

Starburst Effect

stops tends to be those a few stops smaller than wide open.  A lens is “Diffraction Limited” at the f stop beyond which the image begins to soften.   This is a property of the lens and not the camera, but since a lens’ Airy disk is the same absolute size on any camera, the effect tends to be relatively larger and therefore more prominent in cameras with smaller sensors and with higher resolution.   It is great to have all those pixels, but crowding all those smaller elements on the sensor means that the lens will be diffraction limited at a wider f stop.  Physics sucks doesn’t it ?  The properties of every lens/camera combination are different and the only way to determine optimal sharpness is to test it.

The Test

Fortunately, testing lens' for their sharpest f-stop is not difficult.  You start with a target that is flat and has sharp detail.  I used an antique map of Vermont and New Hampshire.  I taped it to the glass on a photograph hanging in the kitchen and then set my camera on a tripod, aligning it so that the plane of the sensor was parallel to the target. I precisely focused on the map using the camera's Live View and used mirror lock-up and a cable release to avoid any vibration. With the camera set on aperture preferred, I  recorded a series of images covering the full range from wide open to the smallest aperture.  The result was a collection of images that I could quickly scan to find where image sharpness began to break down as the f stop increased.

 

The Results

Actually I was pleased to find that the loss of sharpness at small apertures was not as bad as I had expected.  I was able to identify the optimal f stop (usually between f/10 & f/16), but I also got a feeling for how far I could reasonably push the aperture when I needed more depth of field.  For my 100mm Macro, I found that the images were sharpest around f/8 - f/14, but that I could still get reasonable results up to at least f/22.  It is important to remember that this analysis does not take into account the power of sharpening algorithms to salvage sharpness when the results are marginal. 

 

Landscape Dilemma

So what can we do when extreme depth of field is needed?  Sadly I can’t afford a tilt-shift lens, but, now that I know how far I can stop down before diffraction significantly rears its ugly head, I can more intelligently balance the impact of DOF vs. Sharpness and I can apply post processing sharpening to correct some of the problems.  This is also a situation where focus stacking becomes extremely valuable. Multiple images at lower (and sharper) f stops, progressively focused through the scene, can be stacked and blended to get deep DOF with consistent sharpness.  The digital camera once again defeats the apparently immutable laws of physics – take THAT Newton!


 Photography is always a matter of compromise as our artistic vision collides with the limitations imposed by the physical properties of light, optics and camera sensors.  How these limitations are balanced has much to do with the outcome and knowing the most about the capabilities of your equipment is the key to striking the best balance.  Testing your lens' for their optimal sharpness is just one piece of the necessary homework required to get the most from your equipment and the best expression of your vision from the digital Camera.

Read More