Nov
17

The Science and Art of HDR Photography

Introduction

There are very few arts that have had as much influence from science on their creation and improvement as photography.  Having done photography for many years now, I feel that I understand the basics of good photography. I have studied the amazing features of my D700 Nikon DSLR camera and understand how to use them well enough to get a good photo under varying conditions. I have studied composition, lighting, exposure, color and many other topics that are important to good photography.

Even after mastering the aspects of photography, there are still many scenarios where what I see or what I want to emphasize in a scene is considerably different than what is produced by taking a single photo. This is because the relatively simple mechanism by which a camera works cannot reproduce what the human eye working directly with the brain can. For instance, when it comes to capturing and processing scenes of high contrast and widely varying areas of light and darkness, the biochemical and neurological processes which lead to sight are far superior to a simple mechanical aperture exposing some film in a camera (or a photosensor in a digital camera).

Three exposures of some trees and a sunlit cloud. None show the way the scene really looked.

 Until recently, unless you had access to sophisticated and expensive film processing equipment and the considerable time and knowledge required to use it, your only alternative was to say “you had to be there to appreciate it“.  Since the early 1800′s, when photography was invented, photographers have worked very hard to reproduce what they see in their mind’s eye and have used a myriad of techniques to do this. Because of the cost, expertise and time involved, these techniques were not practical though for anyone but the most accomplished of professional photographers. That has changed.

With the advent of the personal computer, the digital camera, and ever more sophisticated image manipulation software applications, almost anyone with some time and a little study can learn to adjust images taken on their digital cameras, including those with highly varying light and dark areas, to produce first class photos. Now you and I can recreate those scenes photographically that previously required the image plus an embellishment of verbal descriptions of how beautiful it was to get the point across. This technique is called High Dynamic Range Photography or simply HDR.

A more realistic image created from the three exposures using HDR photography techniques.

 What is HDR Photography?

HDR photography is a method of combining different exposures of the same scene to allow the photographer to capture a wider range of tonal detail than could be captured by a single shot. Since photography was invented in the early 1880′s, one of the classic problems that photographers have faced was creating a photo that was representative of what the eye could see in scenarios where the shot included areas of intense lighting as well as very dark areas. In such shots the resulting photo might show adequate detail in highly lit areas but the darker areas would all be very dark or black with little or no detail. Alternatively the shot might show detail in the darker areas but the lighter areas would be washed out with little detail.

 Camera vs the Human Eye

Three exposures taken of a poorly lit room which were used to create a composite image using HDR photography.

Dynamic range for a camera can be described in terms of Exposure Value differences between the brightest and darkest parts of an image. In a camera, a combination of the shutter speed and aperture setting controls the exposure.  One purpose of the aperture of a camera is to control the amount of light that is allowed to enter the camera. This limits the brightness of the image by restricting the size of the aperture to stop some of the light from entering the camera. Rather than allowing continuous control of the aperture size, cameras allow the photographer to increase or decrease the size of the camera’s aperture in discrete steps. These are called stops. As you go up the stop scale for a camera, each stop allows 1/2 the light intensity to enter the camera as the previous stop. I did a survey of several photography oriented websites and the consensus regarding the dynamic range of cameras vs the human eyeball measured in stops are as follows. Most point and shoot compact cameras have a dynamic range of 5-7 stops. Most high end SLR cameras have a dynamic range of 8-11 stops. The human eyeball static dynamic range has been estimated to be between 10 to 14 stops.  Given a minute or so to adjust, the human eye can see a total dynamic range of approximately 20 stops.  This is much higher than even the best SLR camera image.

Why do we see more dynamic range than what is shown in the photos we take? It mostly has to do with our brain’s interpretation of the image transmitted to it by the eyeball. The brain and eyes work together in real time to evaluate multiple exposures in a continuous way such that the mind’s eye sees an image that is far superior to what the camera is mechanically capable of capturing in a single moment.

Interior room imaged processed through HDR techniques has much better lighting characteristics.

HDR Photography Can be Learned by Almost Anyone

Due to the great image manipulation tools that have emerged in the last 10 years, HDR photography can now be done by anyone with a camera with basic features like aperture and shutter speed controls. There are a couple of free software applications available for doing HDR.   For the better HDR software you will need to spend from $30 – $700 in software tools depending on how good you want the resulting images to look. Most of these tools offer a 30 day free trial if you want to try this out. There are lots of websites that explain how to do HDR photography in detail so I will just briefly go over the process based on some photography that I did recently that required HDR to make them look correct. For anyone that wants to learn how to do this in very detailed steps, check out the links at the end of this post.

 The Process

  1. Take at least three photos of the same scene but with different exposure settings. One will be taken at the “ideal” exposure for the scene as determined by a light meter or automatically by your camera. One will be taken one F-Stop below the ideal exposure to create an over-exposed photo. One will be taken one F-Stop above the ideal exposure to create an under-exposed photo. Most high end cameras allow you to do this automatically using a feature called automatic exposure braketing.
  2. Move the images to your computer.
  3. Use an HDR software application to merge the photos and adjust the tone mapping using various controls to achieve the desired look.
  4. Correct various problems that are sometimes introduced in the process of merging the photos. Among these are (a) ghosting caused by things moving while you were taking the shots, (b) chromatic abberation caused by the camera lens reacting to different wavelengths of light by offsetting them in shots that were taken, (c) noise that shows up in some areas of the photo as pixels of various colors. There are automated tools that allow you to fix all of these.
  5. Save the image and post it to the desired medium.

The detail of the clouds and the beautiful colors of the foilage cannot be captured in the same image.

 Examples

The examples included with this post include a landscape shot with some trees and a beautifully sunlit cloud, an interior shot, and a landscape with some menacing storm clouds. I have included three shots of different exposures for each along with the final HDR photo. For the shot with the trees and the brightly lit cloud I was able to show the beauty of the cloud with the orange highlights from the late afternoon sunlight while lighting up the trees so that they didn’t show up as a bunch of dark shadows. For the interior shot I was able to use HDR photography to enhance the lighting in the poorly lit room without having to use a bunch of expensive lighting equipment.  For the landscape with the menacing storm clouds I was able to bring out the details and textures in the clouds while still being able to show the color of the trees. It takes a little more time and work to do this but as you can see it is worth it to get a final image that represents pretty much what I saw with my eyes.

With HDR techniques we can capture both the cloud texture and the beautiful foilage colors.

Still a Way to Go But We’re Getting there Fast!

Even with the amazing technology of HDR photography, it is still not quite as good as the eye can see. The physical mediums that we currently use to view photographs like film, high resolution monitors, etc. do not have the dynamic range of human sight. To resolve this issue, HDR techniques currently reduce the range of contrast for the photo while allowing more detail to be seen in the brighter and darker areas than in a traditional photograph. This results in some darkening up the brighter areas and lightening of the darker areas. This means that a really good HDR photograph is tuned to the medium that it will be displayed on. As time goes by though, improvements will be made both in image manipulation capability and in the output media to increase the dynamic range of what can be displayed.

We are already seeing cameras come out with an HDR mode that allows the photographer the option of doing HDR photography in real time with no post processing. The i-Phone 4 was one of the first devices to offer this option on its camera and it works reasonably well considering all you have to do is point and shoot. Now all the major digital camera manufacturers have at least one camera model that offers this feature. Still, if you want to be able to produce amazing HDR photographs on the order that some of the best HDR photographers produce, you will need to invest in a good digital SLR camera as well as some of the software mentioned below and spend some time learning the techniques involved. To me it is certainly worth the investment in both time and money.

Links of Interest and Further Information

Photography Basics

About.com – Photography Basics Article  - Offers a good discussion of the basics of good photography.

LifeHacker Article – How a Digital Camera Works

Photography Basics – A very good photography basics article.

Digital Photography School – A good site with tutorials. Also allows you to submit photos and get the critiqued and to write articles.

The Luminous Landscape – One of the web’s most comprehensive sites devoted to the art of landscape, nature and documentary photography using digital as well as traditional image processing techniques.

The following are four good posts from the same website.

Digital Photography Basics: The Camera

Digital Photography Tips for Beginners

20 Must-Reads for Amateur Photographer

Top 8 Photography Websites

Great Image Software Tools for Producing HDR Photography.

Top 10 HDR Applications for 2011

Essays on What the Eye Sees vs What the Camera Captures

http://www.luminous-landscape.com/columns/eye-camera.shtml

HDR Photography Tutorials

http://www.stuckincustoms.com/hdr-tutorial/ - One of the better HDR tutorials on the Internet.

19 Good Tutorials for Doing HDR Photography

Nov
07

Summer of the Hawk

Hawks of Summer 2011

Birds have fascinated me and my family for many years.  We have had a Double Yellow Headed Amazon Parrot as a pet for over 20 years.  We have always named our computers after bird types.  Our consulting company’s website (http://www.odycc.com/) uses various types of birds as a metaphor for traits necessary to be successful in the use of computer technology to meet your business goals.  Sandra has been inspired by the subject of birds in her artistic endeavors.  An example line drawing of a hawk drawn by Sandra is shown at the end of this post.

A mother Cooper's Hawk looking down at her newly hatched babies in the nest.

You can imagine our pleasure when this summer my family and I had the unique privilege of having a pair of Cooper’s Hawks build a nest at the top of an oak tree in our front yard. Within a few days after the nest was completed, it was apparent that the female had laid eggs in the nest and was sitting on them. After a few more weeks we began to see a behavioral change in the parents. While the female stayed on or near the nest most of the time, the male was constantly out hunting for food. After a couple of more days of observation we began to see little downy heads popping up from time to time, especially when one of the parent birds showed up with a mouse or a lizard for dinner.

It became a daily ritual in our family to check on the hawk nest. As days passed by the baby hawks were rapidly growing. We were able to see more and more of their heads and their gaping mouths as they made themselves available at feeding time. After a couple of weeks the female joined the male in the hunt for food for the demanding chicks. They were extremely dedicated parents, working from sunup to sundown to bring sustenance to the baby birds.

If you do a search on the word “hawk” or “hawk science” in Google or Bing, you will find the search results page littered with aerospace engineering companies, NASA missions, and military hardware or possibly news about a sports team. The very nature of the hawk’s natural abilities evokes a strong symbolism that is appealing to organizations like sports teams or the military. In earlier times, hawks and eagles were symbols of strength and wisdom to Native Americans. Their feathers were used as symbols of social standing and achievement in the tribe. Hawks are swift and alert. They have keen eyesight. The shrill call of a hawk sends smaller creatures scurrying for the safety of shelter. Little did we know that we would be able to observe these qualities and more in the family of hawks that lived in a tree in our front yard in the summer of 2011.

From Crisis to Opportunity

Baby Cooper's Hawk had fallen from the nest into the front lawn.

One hot morning in late June something unanticipated happened. Sandra went out into the front yard to view the nest and found that one of the baby hawks had fallen to the ground. He was lying in the shade in a patch of St. Augustine grass that covers much of our front yard. As she approached the baby bird to determine his status, she found that although he was unable to fly, he was able to walk around on the ground. He seemed to be ok despite falling at least 30 feet! She immediately came back inside the house and informed me and Aaron about the situation.

After taking a look at the small helpless hawk, many questions started racing through my mind. How is this helpless bird going to make it? Will his parents come down to the ground to feed him? How will he survive the hot Texas days on the ground. We had already had 20 days of 100+ degree rainless weather with no relief in sight. Even if he could survive in this harsh environment, how would he escape other predators now that he was in the worst place possible for a baby bird – on the ground.

Baby hawk being coaxed onto a stick so he can be placed back into a tree.

We realized that there was only so much we could do to help. We immediately decided to try to get him off of the ground. I went and got a pair of heavy duty leather gloves and approached the baby hawk. He tried to run but immediately decided he could not escape me so he hunkered down into the grass, opened his wings as wide as possible, and opened his mouth in a threatening gesture. I carefully folded his wings back down over his body and gently grabbed him. I took him over to a low lying branch of a smaller tree and placed him on the branch. Initially he was reluctant to grab onto the branch but after a couple of tries, he did grab on and maintained his balance. He stayed there for the remainder of the afternoon and into the evening. As darkness moved in, I thought to myself that it will be a miracle if he makes it through the night.

Baby hawk after being placed back on a tree branch.

We woke up early the next morning and looked out the window, wondering if he would still be alive. Sure enough, there he was, in the exact same place that we had left him the night before. At least he had sense enough to stay put. Somehow he had managed to avoid detection by predators of the Texas night like cats, raccoons, opossums, snakes, and owls. At first we were extremely happy. We had thought the bird’s chances were very slim and that it probably would not survive the first night. Now that he had survived, a new reality began to sink in. We realized that it would take days if not weeks for this bird to mature enough to fly. How was he going to survive the hot Texas days without nourishment and water? Then it happened. The baby bird began to call out a familiar sound. It was a loud shrill whistle srr-sssrrrrrr. We saw a parent bird circling the area. The baby was calling to its parents. The circles became smaller and smaller as the bird flew lower and lower. Then it landed on a tree branch just above the baby bird. Finally it flew down next to the baby bird and began to feed it what looked like a piece of a small reptile it had caught.

Over the next three weeks this process continued. Both parent birds were involved. One would stay fairly close to the area while the other would go out hunting for food. The parents worked very hard taking care of the birds in the nest as well as the one who had fallen out. It was amazing to see how dedicated these two parent birds were in taking care of their young. They very quickly adapted to the situation. We had a heart felt sense of amazement to be able to witness this.

Ground School and Flight Training

During the course of the next three weeks, the baby bird bailed out of the tree onto the ground several times. We tried to not interfere except when it looked like the baby was wandering into harms way. For instance the tiny hawk tried to cross the hot asphalt street during the busy part of the day. We grabbed it and put it back into the tree before it was inadvertently run over by a neighbor as they were headed home from work. By this time, Aaron had refined the process by getting the baby bird to step onto a parrot cage perch. This was less trauma to the baby bird with less risk to the person (the baby bird was growing rapidly and the beak and claws looked very sharp and menacing).

We did observe that after a three week period, the baby bird finally started making short flights, although we did not see if fly. We speculated that he was able to fly because we would leave him sitting on the low lying branch that had been his home for over two weeks. When we went back out later in the day to see how he was doing, he was gone. Looking around revealed that he was on a branch of the same tree which was five or six feet higher. We would also find him on low lying branches of other trees in the front yard. All throughout this time his parents continued locate him and feed him.

Also after about three weeks after the baby initially fell from the nest, the baby bird’s siblings began to leave the nest. One in particular made a habit of flying down and sitting next to its smaller sibling. At first we thought that the larger bird came down to keep his smaller sibling company, but it also made it more likely he would be fed more often because it was easier for the parents to feed the two birds when they were sitting so close to one another.

The larger chick came down to join its smaller sibling on a lower tree branch.

After another week or two the baby bird increased its mobility until it eventually worked its way back up to the nest and beyond. The hawks stayed in the area for another month or so as the babies learned to fly. In mid August we were blessed with a nice rain storm after months of heat and drought. The resulting gusts of wind were a perfect training exercise for the baby hawks. We spent at least an hour watching the babies following the parent birds as they rode the air currents several hundred feet in the air and then did practice dives toward the tree tops. It reminded me of my childhood dream of wanting desperately to learn to fly like a bird.

As time progressed, the baby hawk moved higher up into the tree top canopy.

After another week we noticed the hawks were gone. Sometimes we could hear their calls in the trees down the street but even this ceased after a couple of days. The only evidence that remains is the large nest that still sits at the top of our oak tree in the front yard. I don’t know if they will be back next spring or not. I hope so. Nevertheless, in the future, when I think of the year 2011 I will always remember the Cooper’s hawks that chose to raise their family in a way that allowed us the amazing experience of being able to observe their way of life so closely.  I have a new found respect for the intelligence and instincts that nature has given these beautiful creatures to successfully raise their young.

One of our last photos of the young Cooper's Hawk calling to its parents for food.

 

"Hawk Landing" by Sandra Ringo

Other Great Resources

Birds in General

http://www.birding.com/ - Lots of information about birds and bird watching around the world.  Contains lots of information about birds in general with many excellent links for further study.

http://www.birding.com/wheretobird/texas.asp - A great resource for bird watchers in Texas.

http://texasbirds.org/ - Website of the Texas Ornithological Society.

http://texasbirds.org/tbrc/statelst.htm#hawks - A list of all the types of hawks found in Texas. 

Hawks

http://www.jaybat.com/birdsahoy/hawks/ - A website that has many excellent links to sites about hawks and other raptors.

http://birdsbybent.com/ch1-10/coopers.html - Everything you want to know about Cooper’s Hawks and more!

Birds and Art

http://www.stanford.edu/group/stanfordbirds/text/essays/Bird_Art.html - A short essay on art inspired by birds.

http://www.stanford.edu/group/stanfordbirds/SUFRAME.html - An interesting website done by that is dedicated to the birds of Stanford.  It emphasizes both the science and art associated with birds.

http://www.hawksaloft.com/ - A website dedicated to the art and science of hawks.  Excellent resource!

http://ottgallerymv.com/lannymcdowellavianart/index.php/2009/07/raptor-photos-young-coopers-hawks-on-marthas-vineyard/ - Some great photography of some Cooper’s Hawks and their babies on Martha’s Vinyard.

     Copyright © 2011-2012 by Danny and Sandra Ringo.  All rights reserved.  Articles may not be reproduced without permission.