Sunday, June 9, 2013

HDR Photography, Overused or Underappreciated?

5 Shot HDR (+/- 3 EV)
Today's digital camera sensors have a limited dynamic range when compared to human vision.  A digital camera sensor can only record a range of 10 stops of light at a time.  There are times where a scene has a bright light source as well as dark shadows creating a greater dynamic range than what a digital camera sensor can read.  Where human eyes can see detail in both the shadows and highlights at the same time, a camera sensor can not and the photo may not come out as expected.  When taking a photo of a scene like this it is necessary to "clip" or lose detail in either the shadows or the highlights.  This causes completely black or white areas of an image depending on where you set your exposure.

High Dynamic Range (HDR) photography is a technique in modern digital photography that allows larger range of tones to be shown than can be recorded in a single exposure.  This is done by taking multiple images of the same scene by bracketing exposures, taking an underexposed image at -1 EV, a normal exposure at 0 EV, and an overexposed image at +1 EV.  More images can be taken at further extremes but generally the +/- 3 EV is the farthest it is necessary to go.  It is best to take all of the bracketed exposures in succession and without moving the camera to prevent issues with post-processing.  It is not necessary to use a tripod but it does help during the alignment in post-processing and is necessary for longer exposures.   

In the years since the advent of the HDR photography, some say it has become overused and overdone and will immediately dismiss and belittle a photographer for using the technique.  A lot of this stems from the ability to overdo HDR processing and using the HDR technique for situations for which it isn't called for.  HDR photography is not going to improve a badly composed image and it isn't the end all be all of photography techniques, rather a tool to be used if the need arises. 

3 Shot HDR (+/- 1 EV)
An important part of HDR photography is restraint.  For example, if a scene can be fully captured with one image, great, no need to do exposure bracketing and use the HDR technique.  However, if both the highlights and the shadows are clipped, bracketing and HDR may be a good idea.  Get used to looking at your histogram and being able to tell the difference between a situation where nothing is being clipped, the shadows are being clipped, the highlights are being clipped, or both the shadows and highlights are being clipped.  When you are in the field, train yourself to think in terms of how the exposure will look on the camera.  To help with this, after taking an exposure look at the histogram for each photo on your camera and based off of what you see, decide if it is worth bracketing exposures and to use the HDR technique.  I tend to use the HDR technique during sunset or sunrise when I'd like to include the sun or colors in the sky in my exposure as well as foreground shadow detail. 

Once you've taken your bracketed exposures, the rest of the HDR process is accomplished in the digital darkroom.  There are 3 programs which will help create a final image from bracketed shots, Adobe Photoshop CS 6, Photomatix, and Nik HDR Efex Pro 2.  All 3 do a good job and there are plenty of tutorials on how to use all of them.  Personally I prefer Nik's HDR Efex Pro which does a great job with creating a good base image that can then be modified to your liking.  Photoshop does a good job with preventing "ghosting" which can be caused if there are discrepancies between your bracketed exposures.  What these programs all have in common is that they take the bracketed exposures, align them, and merge them together into one image.  They then selectively allow you to keep the highlight detail in the greater exposed image while keeping the shadow detail in the lesser exposed image.  The final product is an image that no longer has any highlight or shadow clipping.  This helps to create vibrant colors in the sky of a sunset as well as rich details in the shadows.  It is, however, very easy to overdo it with HDR photography processing.

My best advice is to make the photo look as realistic as possible and to only use as much compression as necessary to avoid highlight clipping.  Think of HDR photography as another tool in your toolbox, a way to help capture a scene the way you experience it.  Use it to your advantage and keep the processing to a minimum and I think you'll agree that HDR processing is here to stay.  

5 Shot HDR (+/- 3 EV)

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