Dynamic Range, What is it?

Dynamic range of Light, is a term that has been used extensively with digital photography over the last few years. Specifically in context with a high dynamic range. It is also a term that is very misunderstood and a lot people see it as a style of photography. In the same way they see a Monochrome photograph as a way to edit a color photograph to create a different look. Where I think photographers get it wrong is they believe that any photograph can be processed in a way to create a HDR image. This is not true and to understand why. I have to explain from the start how HDR was developed to solve the basic limitations of a digital camera.

High & Low Dynamic Range

Very simply, dynamic range is the difference between the brightest and darkest areas of a scene you intend to photograph. This difference can be measured and we use stops of Light to gauge this difference in Dynamic range.

A High dynamic range, is when the range of light or luminosity of a scene being photographed is greater than the abilities of you camera. So you cannot find a single exposure that can capture the whole range of light.

A Low dynamic range, is when the range of light or luminosity of a scene being photographed falls when in the capabilities of your camera.

So central to this is actually knowing what the dynamic range is of the camera you are using.

What is the Dynamic Range of my Camera?

Well the easiest way to find out is to pop onto google and type in “what is the dynamic range for (your camera brand and model).

If you interested in knowing how to find out the dynamic range of your camera and how google knows what the dynamic range is, follow the steps below. (you will need a 18% grey card, which is often used for white balance correction)

  • Setup the cameras exposure to to render the 18% grey card completely white. (not completely blown out white, one stop less than that)
  • Then systematically photograph that Grey card and between each exposure, stop down (under expose) by one whole stop.
  • Counting each of these stop as 1.
  • Till the point is reached that the 18% grey card is completely exposed as black.
  • Tally yo the total amounts of stops between the white exposure and the black exposure, is your camera’s dynamic range.
  • Most modern camera’s are between 9 through to 13 stops.

What does that really mean? A real life definition …

Well simply put its the reason why some scene are so absolutely frustrating to photographing and other are not. Let me paint a scene for you.

You find a pride of Lions sleeping on an open plain/savannah and you lift your camera to take a photograph. The scene in front of you has a dynamic range of 18 Stops of light and your camera only has a dynamic range of 11.

First problem

The camera will take an exposure reading from the same location as its focus point, which will be on the Lions. The Lions will be correctly exposed and because 7 stops of light is beyond the cameras dynamic range. Everything brighter than the Lions will be over exposed (read the Sky).

Second Problem

The alternative is to take exposure off the sky. However, because we are still missing 7 stops of light. This results in the sky correctly exposed and everything darker than the sky being underexposed (read the Lions).

Dynamic range of Light: The Frustration

Even more frustrating is that our (human) eyes can see 22 to 24 stops of light. So when we look at this seen we can easily see the lions and see the pretty setting sun as a back drop. For novice photographers this is beyond frustrating, because why can my camera not capture the scene as I see it … well simply the camera does not have the dynamic range to photograph that seen.

Solutions to the problem

Solving the riddle of the missing 7

So how can we solve the problem of the missing 7 stops of light. Well there is a number of solutions. Which I will share in more depth in later posts. So for know here is a quick run down of options.

  • Take two images and blend. 11 stops of light + 11 stops of light = 22 stops of light, great we get our 18 stops (and extra). This is something Landscape photographers have been doing for years.
  • Take one middle exposure, create two copies of that one exposure and blend that. Same math as above, however the file will not be as clean. But it solves the wildlife photographers problem of movement between frames.
  • Take one exposure and work with the limited stops of light. Which means either loosing information in the shadows or highlights. This is often referred to as high key or low key images.

This image is two copies of one file blended together to achieve correct dynamic range for this scene.

I really do hope this helps settle some frustrations out there when trying to photograph scenes beyond your cameras capabilities.



P.S these images were taken with a Canon 50D way back when with a 100-400mk 1, so the Image quality is what it is …

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