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21 Oct 2021

HDR Photography

h d r photography
HDR stands for High Dynamic Range, meaning quite simply, "a high level of contrast". HDR photography, therefore, is photography that captures a very high level of contrast, including very bright highlights that still have detail instead of being pure white, and very deep shadows that still have detail instead of being pure black. HDR photography is often captured by capturing multiple images at different exposures and blending them together, however many modern cameras can capture high dynamic range images in a single exposure.

What Is HDR?

High Dynamic Range (HDR) photography produces an image with a broader range of tonal detail than would normally be produced by a single image from your average camera. In this article, we are going to discuss exactly what is HDR and what types of scenes have a high dynamic range to begin with.

Dynamic range simply refers to the range of light in a scene from the darkest shadows to the brightest highlights. A scene that has a high dynamic range simply means that there is an extremely broad range from the darkest shadow to the brightest highlight. The problem with cameras is that their dynamic range is fairly limited (at least when compared to our eyes). This means that if you are able to see detail in the shadows, then your highlights are typically completely white or "blown out." Vice-versa, if you can see details in the highlights, generally the shadows become fully blackened or "clipped." The goal of an HDR photograph is to capture more of this dynamic range than would not be possible with a single image.

Dynamic Range Of The Human Eye

The human eye has an incredible dynamic range that is estimated to be around 20 stops. A stop is simply a measurement of light that will be further explained in a later article within this HDR series. The dynamic range of the human eye is significantly broader than most DSLR cameras with ranges between 10-14 stops.

For example, take a moment and look at the room around you. Most likely, you will see a room with bright highlights where you have lighting (be it a window or tungsten light) and you will also see dark shadows where the light isn't falling. However, our eyes can generally see the entire dynamic range within a scene like this. Meaning, you can see details in the shadows and simultaneously see the detail in the highlights. Take a moment and walk outside, after your eyes adjust, you can once again see all the detail in the shadows and the highlights (even when looking in the direction of the sun).

However, in these same scenes, the average camera is only going to see a portion of that 20 stop range. For example, if your camera has a dynamic range of 10 stops, then the camera will see half of the range that your eyes would see. Let's relate this to our examples. If you are inside, and you are trying to see the detail in the shadow areas of your room, your camera is going to reach a limit where everything brighter than that 10 stop range will be completely blown out. Likewise, stepping outside, if you wanted to capture the detail in the clouds and bright sky, the camera will not be able to show detail in the darker shadows that are below the horizon line.

I am sure you have all had the experience of trying to take a portrait of a friend standing in front of a beautiful sunset. Remember how that shot always turns out? Either your friend is nice and bright, and the sky behind him/her goes completely white, or the sky looks amazing and colorful and your friend is pitch black.

All Cameras Are Not Equal

DSLR Cameras that have a broader range are generally more expensive. Sensor technology is getting better and better which allows the latest cameras to have a higher dynamic range. More recently, Nikon is currently the leading brand when it comes to highest dynamic range with the Nikon D800 having a dynamic range of 14.4 EV (Stops), whereas the locale="us"]Canon EOS 5D Mark III has a range of 11.7 EV.

HDR History (More Technical Background)

When the term "HDR photography" was first coined, it only referred to a photographic technique which overcame the limitations of existing cameras: If you set your exposure so to preserve details in your highlights, many scenes were too contrasty and the shadows in that scene would be pure black with no detail. The same was true for exposing for your shadows: If you made sure to choose an exposure that obtained detail in the darkest shadows of a scene, the brightest parts of that scene would most surely "blown out", or pure white.

This shortcoming was defeated by bracketing the camera's exposure, usually with three or more images captured; one that fully preserved highlight detail, one that fully preserved shadow detail, and one or more somewhere in between, just for good measure.

These different exposures could be layered on top of each other in Photoshop, and blended together to create one single image that preserved details from the brightest highlight to the deepest shadow. The images had to be captured from a tripod, of course, in order to blend correctly. (And even then, any motion in the scene would still create errors in the blending process)

In recent years, however, modern digital cameras have increased the dynamic range capability of a single exposure by many, many EVs or stops. Thanks to various advancements in digital sensor technology, many digital cameras can capture fine quality details in both bright highlights and deep shadows with a single exposure.

Despite the lack of bracketed exposures and special HDR software, the resulting image from such a single exposure is often still called an HDR image, simply because of the level of detail it captures.

HDR photography went through an initial fad phase among photographers, and HDR processing was often highly unrealistic and the subject of much debate. Lately, however, HDR photography does not necessarily denote an over-processed image with unnatural looking highlights and shadows, it is simply the overall genre of photography in which high dynamic range is captured by any means, whether the results appear natural or "candied".

Conclusion

HDR photography has the potential to produce images that are closer to what we can see with the naked eye (or beyond if they are processed too far), with crisp detail visible in all ranges of light. Again, in this HDR series, we will discuss several techniques to broaden the dynamic range of your images.

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