Bracketing, HDR, and JPEGs.

Dolphin statue Kelowna waterfront made from 7 images bracketed one stop apart.

Understanding light is an essential part of improving your photography skills.  Why is one image underexposed and another not?  How is it that some shadows have no details and some highlight areas are blown out?  What is HDR and how is bracketing involved?

Both film and digital media are limited in the range of darks and whites that can be captured.  Something too dark or too white leaves a detail void in an image; too dark means no details in shadows and too white means no details in highlights.  Neither is preferable and yet, in contrasty environments, one or both often occur.  This has to do with the media's ability to accurately represent the amount of light, or lack of it, coming from an area.  

There are several ways to overcome this.  The simplest way is to use RAW file formats and correct for shadow and highlight extremes in a good pixel editing program like Photoshop or Lightroom.  You can make some small corrections in-camera with JPEGs and image control, but it pales in comparison.  Another way is to bracket the exposure, taking a number (usually 3, 5, or 7) of images, each a stop apart.  This can be done manually or automatically if your camera has a bracket feature.

Some cameras also have a built-in HDR program but I find combining the images in something like Photoshop or Photomatix is the best method.  Dark areas reveal details when overexposed and light areas reveal them when underexposed.  Combine the images to get the best of both worlds.  The greater the contrast, the wider you need to bracket.  Often +3 and -3 with seven shots (as above) is enough, but you can do as many as you want (-=+10 to -10 with 11 shots at 2 spots apart).  The interesting thing about HDR is that, depending on the program, you can produce some amazing results.

A JPEG is capable of only capturing 8 stops of light from white to black.  RAW files can still extract details two stops on either side of this, so around 12 stops in total (depending on the camera - not all RAW images are the same).  If you are getting harsh shadows and/or highlights you may want to consider using RAW formats or going to HDR.  Both require a certain approach and will involve a steep learning curve.  However, these will also improve your understanding of light and image capture, which is what this blog is all about.

Thanks for reading. 

Eric Svendsen     www.ericspix.com

 

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