Traveling with Explorer of Light George Lepp Part 3: Using ISO as a Tool

March 29, 2011

The most interesting activities typically happen in the low-light conditions of early morning or evening.

This is the third part of a three-part series on shooting techniques, written for the Canon Digital Learning Center by George Lepp:

  1. Shooting from Unstable Platforms (click to read)
  2. Panoramas: Going to Great Lengths (click to read)
  3. Using ISO as a Tool

You know I love to anticipate, use, and tell you about every new device and technology of the digital age. The digital toolbox offers so many creative and technical options that it’s hard to keep track of the possibilities, much less explore them all. But you really need to know about one of the most revolutionary and versatile new digital tools, Extended ISO, which has reached new levels of capability with Canon’s new sensor and DIGIC 4 processor in the EOS 5D Mark II. Digital ISO is now a reliable answer to three persistent challenges inherent to outdoor and nature photography: capturing in low light, stopping action, and achieving greater depth of field.

What’s new about ISO?

The International Organization for Standardization determines and issues world-wide industrial and commercial standards. Photographic ISO is a numerical value that describes the sensitivity of the medium and the speed with which photographic information is recorded— on film, or on a digital processor. In films, higher sensitivity and speed are associated with larger grains of silver halide (the light-gathering crystals) in the film emulsion. In digital processors, higher ISO is a function of increasing the electrical charge and light-gathering capabilities of each pixel on the sensor.

The first professional photographic transparency films had very low ISOs. I’m not old enough to have used the original Kodachrome (ISO 6), but it would have been excruciatingly slow and very constraining both technically and creatively. I started with Kodachrome 25 (ISO 25), which limited outdoor photography to bright days and/or long exposures (remember the sun over your shoulder rule?). Between Kodak and Fuji, we progressed to excellent films in the ISO 50 (Fuji Velvia) to ISO 100 range (Fuji Provia, Kodak E100VS and E100G). To achieve faster speeds, serious photographers either “push-processed” 100 speed film to 200, or used slide films such as Ektachrome/Kodachrome 200. These reliable films are still in use today. Another solution for low-light film photography, such as in indoor sports, has been to use some of the faster print film emulsions. These offer more speed, less grain, and are able to circumvent the inherent color variations of different light sources

Slide and print films with higher ISOs (400 and above), while faster, yield completely unacceptable results due to their high contrast, diminished color, and image-softening, detail-obliterating graininess. Some photographers have used these higher-ISO films to create specific effects because of their exaggerated grain.

High-ISO digital captures present similar aberrations called “noise.” Luminance noise, the most prominent type of noise, gives an effect like film grain: colorless, granular variations in lightness. Luminance noise isn’t all bad; it’s the source of some of the textural detail in an image. Chrominance noise, the more damaging type of noise, is an array of green, magenta, and blue specks most obvious in un-detailed expanses, such as the sky. The victims of excessive digital noise are sharpness and true color.

The first digital SLRs offered only slight improvements in the quality of images captured at higher ISOs, but each successive generation has improved capability. Today’s DSLRs are offering ISOs as high as 25,600! In reality, these highest numbers are ISOs of last resort, but don’t underestimate the progress that has been made. We’ve now reached a point where photographers are regularly publishing quality images captured in the range of 400 to 3200 ISO.

The Higher ISO Advantage

Photographers love to say, “It’s all about the light” as if it were a profound insight into the very essence of photography. Increasing ISO is all about maximizing the light. It’s especially relevant to outdoor photography.

Consider the nature of nature photography. It has its dark side. You’re at the mercy of the elements. You can predict the sunrise, sunset, and angle of the sun, but you can’t stop the clouds or the onset of night. Your animal subjects are operating on their own clocks, in their own realms, and for their own purposes. You can’t position them in the spotlight as you could a studio model.

For many of us, capturing the spirit of natural subjects means to portray their behavior and movement in ways most people never see. The most interesting activities typically happen in the low-light conditions of early morning or evening. Stopping action means fast shutter speeds, but in low light we quickly run out of f/stops.

Depth of field is a problem for most subjects, but especially in macro photography, where the higher the magnification, the greater the light loss at the film or sensor. In landscape, we want both the foreground and the distant mountains to be in sharp focus. Rendering all of the subjects in a herd of animals or flock of birds in focus requires depth of field beyond the capabilities of a wide-open lens.

Extended ISOs can help us to address all of these challenges to successful outdoor photography.

Shooting in the dark

Think of how you would normally approach a poorly lit subject. You’d throw light on it (flash or floods). Or you’d put your camera and lens on a tripod and take a really long exposure. But what if you can’t?

One of the reasons I’ve been so intrigued by the marble caves of Lago General Carrera in Patagonia (featured in Parts 1 and 2 of this series), is that without today’s digital tools it would be impossible to photograph them successfully. The caves are accessible only by water, and their labyrinths are eerily illuminated by intermittent bright openings to the outside and reflections off the clear, azure water. Shooting in shadows from a constantly shifting boat, I could not set up a tripod. Even if it were possible to cover the large area, flash would have destroyed the eerie natural lighting. The answer was a camera that would allow me to choose higher ISO and to maximize the quality of the beautiful light that was available.

My perspective was limited by the need to use a wide-angle lens to capture the caves at close range. Working with a Canon EOS 5D Mark II at ISOs of 800 and sometimes higher, I was able to achieve the necessary shutter speed of 1/60 sec. to mitigate the motion of the boat while allowing enough depth of field at f/11 to render the complex structures of the cave fully in focus. The resulting images could never have been captured on film.

But there’s more! The 5D Mark II shoots high definition video too. Its capture rate is set at 30 frames per second, normally between 1/30 and 1/125 sec., and it automatically adjusts the ISO and the aperture to achieve sharp and well-exposed footage. So as we were moving into and through the dimly lit caves, with light reflecting off marble faces, the water, and in blinding blasts from intermittent “windows,” the 5D Mark II’s video capture used the camera’s ISO capabilities (all the way to 6400 ISO) to continually adjust to the dramatically changing conditions. It’s also possible for the EOS 5D Mark II and many other recent models to set ISO automatically for still images. With the 5D Mark II, in P, Av, or Tv modes, if you set Auto ISO, the camera will adjust the ISO up to 6400 to maintain a shutter speed that corresponds to the focal length of the lens being used. For example, if you are working with a 24mm lens, the automated program will try to maintain a shutter speed of 1/25 sec. or faster by adjusting the ISO. It’s a tremendous advantage when the action is fast and the light is changing quickly.

Shooting on the fly

By now you should be thinking about the different ways you could apply this new tool to your photography. I think it’s a great asset for wildlife photography, and it has actually allowed me to achieve some shots of flying birds that I never thought would be possible.

For years I showed in my programs a photograph of a black skimmer—beak open, its lower mandible cutting through the water—as an illustration for the discussion about digital ethics. I suggested that if I had used Photoshop to insert a fish into the skimmer’s mouth, I would have been violating the ethical code of nature photography because I would have been suggesting something happened that did not. In fact, I posited that inserting the fish would be very risky business since as far as I knew no one had captured a skimmer in the act and it was not at all clear how the fish enters the beak.

But in November 2007, armed with a hand-held Canon EOS 1D Mk III and an EF 500mm f/4L IS lens, I staked out a pond in the Okavango Delta where a group of rare African skimmers were looking for breakfast. With a combination of predictive autofocus and a fast shutter speed (1/3000 sec.), raising the ISO to 800 allowed enough depth of field to keep the whole bird in focus (f/9.5). I followed the birds at ten frames per second as they approached. The best of the resulting images is an eight-frame series of perfectly sharp images showing one skimmer slicing the water, capturing a small fish, and coming up off the pond. The 800 ISO was an instrumental factor: it allowed the 1/3000 sec. capture at f/9.5. As we reviewed the series at high magnification, we learned that skimmers (or at least that skimmer) tuck their heads down as they catch a fish—not the process I would have imagined.

I now routinely use 200 and 400 ISO for any wildlife photography. Consider the hippopotamus: usually out in the open, in bright light, moving slowly. Why is it so hard to get a good hippo shot? Because you don’t want just a hippo lump in the water. You want the action, a rearing hippo, mouth open, water spraying everywhere. Using 400 ISO allows the option of action-stopping shutter speeds of 1/750 to 1/1000 sec., with enough depth of field to get the whole hippo in focus. If the action becomes furious, I wouldn’t hesitate to increase my ISO to 800. I feel there is minimal loss of quality at these ISOs: it’s win-win.

Shooting with depth

Anytime you need a smaller f/stop to achieve greater depth of field, higher ISO is an option. This is definitely the case in macro photography with natural light, but it’s also true in landscapes, especially when wind is a factor and you need both a faster shutter speed and depth of field.

I love to chase butterflies with a telephoto lens. Due to the high magnification of the telephoto, the butterfly fills the frame and a smaller f/stop is necessary to get as much as possible of the butterfly’s spread wings in focus.

Add to the situation my own movement and the constant movement of my flighty subject and you have a fairly complicated set of problems to solve. A higher ISO, again, allows the smaller f/stop for depth and the faster shutter speed to stop the movements.

Higher ISO can help you to achieve a landscape that is sharp from foreground flowers to distant peaks. A small aperture is sometimes needed to maximize the depth of field, even with such tools as wide-angle and tilt/shift lenses. 

If you’re shooting without a tripod, in low light, or in windy conditions, you’ll need a fast shutter speed as well. Throw in a polarizing filter losing two stops of light, and you really need a higher ISO to make it all work.

New tools = new rules

Making the most of advanced digital ISO capability means thinking about your photography differently. New rules:

  • Embrace the latest technology. Yup, this means you might have to spring for a new camera with serious ISO capabilities.
  • Consider your options. Review your image library with a view towards identifying the photographic situations that would have benefited from expanded ISO capability. This will help you identify opportunities in the field.
  • Be realistic about your camera’s high-ISO capabilities. Test it under controlled conditions before you head into the field. Cameras with larger sensors and more powerful processors will achieve better high-ISO captures. Don’t be afraid to experiment with the higher ISO settings; know what your camera can do.
  • Know your camera’s built-in High ISO Noise Reduction capabilities. Most modern digital SLRs have settings to control the amount of noise reduction applied in-camera, or the default level to be applied to RAW images when they’re processed. Don’t immediately assume the maximum noise reduction is best — it usually works by blurring Luminance noise, and thus blurring detail. Test it at different ISO settings, so you know how it performs for you.
  • Set your standards. Critically evaluate your test captures at 1:1 on your computer screen, and with 8 ½ x 11 prints. If you make larger prints, blow up a section of your test images and print at 8 ½ x 11 for comparison purposes.
  • Consider the ultimate use. Excessive noise will be more evident in large prints and less visible in small prints, web-postings, or projected images.
  • Be ready to process post-capture. At very high ISOs, you’ll need to correct noise-related image anomalies in noise-reduction software.

Sometimes it’s hard to choose between the photographic tools we’ve already mastered—those comfortable old companions on so many outdoor treks—and new techniques and equipment that challenge our routines. You know I love to try everything new, but that’s my job! (Somebody has to do it.) For most photographers, it can be difficult to buy into and master each new technology. But there’s no doubt whatsoever about the advantages offered by the ISO capabilities in newer DSLRs. They’ll help every outdoor photographer meet the challenges of the field, and they’re well worth the investment.

Written by George D. Lepp. George Lepp, one of North America’s best-known outdoor and nature photographers, is a Canon Explorer of Light, and a popular lecturer and teacher. He is also the author of many published books and articles and the field editor of both PC Photo and Outdoor Photographer magazines, where his “Tech Tips” column is widely read. Learn more about George at the Canon Explorers of Light Gallery and at


The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

All images are copyright George Lepp

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