Some thoughts on High Dynamic Range (HDR)

February 18, 2009

To speak about High Dynamic Range we first need to define what we mean by Dynamic Range.

In photography your dynamic range (which is used in other fields such as music, electronics, and meteorology) is referring to luminescence.    This is relative luminescence as we can capture scenes which are very dark (night scenes) to very bright (working with strobes) on the same piece of film.   The dynamic range of your imaging substrate (film, digital backs, etc) describes what contrast ratio you can capture based on the scene and more specifically what element of the scene you choose to meter.

Imagine a black cat sitting on a white crumpled sheet illuminated by bright sunlight.   The cat’s fur has texture, the sheet has texture.   Your eyes can see both the texture of the sheet and the cat at the same time but if you tried taking a picture of the cat you would generally end up with a silouette of a cat and texture in the sheets or you’d capture the texture of the cat but knock the background out to a featureless white tone.

Morgan, floating cat

The purpose of High Dynamic Range techniques are to provide tone in all areas for scenes in which the range of luminescence is longer than the media can support.    While there are a number of techniques used for film (such as using a graduated neutral density filter) for common scenes such as landscapes where the sky is much brighter than the land digital has really allowed things to take off through tone mapping.   This allows a photographer to bracket their exposure by a number of stops to get the “correct” exposure for every area in the scene.  Using a tripod to ensure that each frame is identical except for the exposure the photographer can then combine those images using software.

Photo by David Cornejo (reposted under CC license)

This is an excellent example of the technique.   The scene had strong sunlight coming from above so the walls would have been in shadow.   By exposing for each area of the scene and using some commonly available software the photographer was able to open up the shadows to give us full detail.

I recently took a course at ICP for portrait photography with Ken Collins.   One of the books he suggested was In Praise Of Shadows which was his way of suggesting that we learn to love negative space.   HDR is the antithesis of negative space.

By opening up all areas you exterminate shadows.

One of the things you have to do in photography or any art form is to make choices.   For photography these choices are composition and exposure.   In many real world cases you have to decide what is the most important element in your composition and set your exposure to put that element in the zone you want it to be in.   Unless its an overcast, low contrast day, this will often consign other elements in the scene to the shadows or highlights where they may loose all detail.   HDR says that we don’t need to make that choice and I think that its a good thing.

Cat, Cave Art Space

Here we have lost detail in both the floor and in the curtain in the background.   The cat was the most important element to me so I chose to expose for the cat.   I don’t think the photo is poorer for it.  The floor and curtain were reduced to geometric shapes which we can orient our subject around or in.

Mr. Cat in the loft

Again, we’ve lost most of the tone in the sheet at the bottom of the frame which creates empty space.   This shoots our eye right up to the main subject, the lounging cat.    Negative space is used to direct attention.

Fire Eating, Starshine Burlesque

Without the negative space in this photo we couldn’t trace the arc of the fire eater’s torch.  The empty space allows the viewer to draw the motion.   If the background had detail it would be far too distracting and we would loose the detail of the flame.

Neck Face, Williamsburg

Do we loose anything in the shadows?   In this case would we gain by seeing the brick wall of the building in the background or every detail of the motorcycle in front?   Should we see clouds in the sky at the bottom of the street?   What would we really gain?

In the end we’re limited creatures using tools that don’t measure up to our eyes.  Those limits force us to make choices.   What can I take away from this moment in time?   What’s important?  What can be left behind?  We’re not richer for not having to make those choices.   HDR is an interesting and occasionally pretty technique but I don’t think it helps us in the long run.   Taking everything away from a scene leaves nothing of yourself in it.   What’s the point of taking the photo in the first place if not to let people know what you thought of it?

Posted in Technique