Realistic HDR

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  • What is Realistic HDR?
  • When and how to produce it

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Realistic HDR - part 2


What is Realistic HDR? - Part 1 taking the shots

HDR is the acronym for High Dynamic Range.

In digital photography HDR is used to describe the technique of merging several differing exposures of the same scene in order to capture the total range of tones from the darkest to lightest.

Sometimes this range is above and beyond what the camera sensor can capture in a single exposure - whereas the human eye witnessing the scene has a greater dynamic range so the single exposure image will not accurately reproduce the scene as witnessed and remembered.

By taking serval differing exposures and using software to merge them later in to a single image then a close approximation to the original scene can be reproduced - this is Realistic HDR.

This should not be confused with the over-processed tone-mapped surrealistic images with extreme colour saturation and halos which can also be achieved by HDR processing which unfortunately has become somewhat synonymous with the term "HDR" .

Consider the photo above which is an example of a realistic HDR image.

Now compare and contrast it to the image below which is a standard single exposure image of the same scene.

It can be observed that the realistic HDR image has a lot more detail in both the brightest and the darkest parts of the image. Depending on the composition and subject material of an image it may not be necessary to reveal details in all parts of the image - but in a photo composition like this one the view from the window (revealing both the weather conditions and the spectacular panoramic view across to the distant sea) and the detail in the shadow areas (revealing the flaking paint, graffiti and the dilapidated nature of the building) are equally important as the primary subject (the man) as they help place him into the context of the composition.

For the composition to work, it was therefore necessary to correctly expose for both the shadow and highlight areas as well as the primary subject. 

The problem is that without the careful addition of additional lighting the camera simply cannot record the full range of luminance levels of the scene - so any single exposure has to be a compromise with details lost either from the brightest or darkest areas (or as in this case, both!)

This is where realistic HDR comes in - as the technique enables the full range of luminance levels to be recorded and merged together in a single image - the intention to actually recreate the scene as it was actually perceived by the naked eye at the time. (The human eye is capable of registering many more luminance levels in a scene than that of a camera sensor or film)

The top image is an accurate reflection of how I remember the scene in reality.

Realistic HDR - How to produce it

There are two distinct and equally important aspects to producing a realistic HDR image

  • How to set up and take the shot(s)
  • How to combine and edit the resultant image in post processing

The rest of this page deals primarily with taking the shots.

Processing the final HDR image is covered in Realistic HDR - part 2

Equipment needed for realistic HDR digital photography - taking the photos

You will need (ideally)

  • A digital SLR (although any camera over which you have manual control over exposure may be used)
  • A tripod (or other method of to avoid hand holding the camera)
  • A cable release (or use the self timer to avoid camera shake as you activate the shutter

How to set for realistic HDR digital photography

A good way to determine whether your planned photo is a good candidate for realistic HDR is as follows:

  1. Make sure you shoot in RAW format
  2. Compose the shot, with the camera in Av mode and the aperture set to give the depth of field you desire. Use the lowest ISO setting and evaluative metering (matrix metering for Nikon users).
  3. Take the shot and then review the image alongside its histogram (see below)

The image captured with exposure determined by the camera's evaluative metering along with the histogram for the image.

The key thing when looking at the histogram is that it can be seen to touch at both the left hand edge (the darkest tones) and the right hand hand (the brightest tones). This confirms that which is apparent when simply viewing the image on the lcd monitor of the camera - that the brightest tones are overexposed and thus "blown out" (lacking any detail) and the darkest tones in the shadows are also pure black and so also lacking any detail.

When I compared this to what I was seeing with my eyes at the time I could see that this did not faithfully recreate the scene as I was perceiving it  - with a view from the window revealing blue summer skies and a distant view of the sea and inside the building considerably more details in the darker shadow areas.

So I knew that this was a good time to resort to Realistic HDR.

Realistic HDR - setting the exposures

It is best to shoot only as many exposures as necessary to capture all the luminance levels in the scene.

Begin for exposing for the brightest parts of the image

  1. To do this switch the exposure mode to manual and dial in the aperture that you had previously selected. 
  2. Switch on the live view and view the histogram as well as image (see your camera manual for instructions - for Canon DSRL users press the "info" button until the histogram is visible).
  3. Dial down the shutter speed until the histogram no longer reaches the right hand side (note if the sun or a very bright light source is in the scene do not worry if a single high peak of luminance levels remains at the right had side)
  4. Switch off the live view and using  a shutter release or self-timer take the first exposure.
  5. Check the image and histogram on the lcd screen and ensure the histogram doesn't reach the right hand edge.
  6. Continue to take shots increasing exposure in 1 stop intervals (dial the shutter speed in 3 click increments to slower shutter speeds).
  7. Review each image until the the histogram no longer reaches the left hand edge - this will be the most over exposed image of the set.

These will be the shots that you will merge together later to form the final realistic HDR image.

The image below shows the images and exposure details that formed the final HDR image shown at the top of this page

You now have the shots you need to merge into a realistic HDR image.

The process for doing this is covered in Realistic HDR - part 2

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Other useful links from this page

go to JARGON BUSTER digital photography terms explained

Go to Realistic HDR part 2

Return from Realistic HDR to Digital photography techniques

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