High Dynamic Range (HDR) photography is a method for capturing scenes with a range of brightness levels that exceed the camera's dynamic range (DR).  HDR images are created by blending several exposures of a scene at different exposure levels -- a bracket -- in a specialty program designed for that purpose.  The market offers many software programs that automate the blending process, and there are a plethora of online tutorials describing the bracketing process.  One of the best is Cambridge In Color's tutorial.

There are two essential requirements for a successful HDR bracket.  The first is to have at least one image that does not result in saturated ("blown out") out whites.  Also, other exposures should try to capture as much of the scene's dynamic range as possible while keeping shadow noise low in dark areas.  But, how does one go about doing both?  As good as the above tutorials are they don't always provide specifics on how to meter a scene for HDR and how to set up the camera for a bracket that meets both goals.  Based on my experience, the steps below provide a straightforward how-to approach to HDR metering and bracketing.  They include guidelines for:

• Determining overall scene brightness range.

• Choosing the number of images to include in the bracket.

• Determining how big bracket increments should be.

• Deciding where to set the exposure midpoint.

Note that exposure bracketing is not always needed.  If the scene EV range is within the camera's dynamic range at the chosen shutter speed the scene can be captured with a single exposure -- although a bracket will minimize dark area noise.  There, a histogram can provide a useful visual check.  Visit photonstophotos.net to find the DR of many cameras.

Finally, a tip of the authorial hat to the Photomatix HDR Tutorial for Real Estate Photography, which deals with very high contrast scenes such as those encountered when photographing interiors that also include a window with a view to a daylit scene outside.  The page even includes a link to an HDR Exposure Calculator that provides exposure settings for a use defined scene.  We came across this reference after deriving the same procedure from personal experience.

It is helpful if the camera has a continuous drive mode and the ability to perform shutter speed bracketing.  Otherwise, important steps must be performed manually.  A spot meter helps during exposure metering by isolating metered areas, typically the brightest and darkest in the image.  A histogram can serve as an alternative, albeit used a little differently.  (The above referenced Photomatix tutorial describes how to use a histogram to establish exposures.)  A zoom lens is useful in the metering process although it is by no means essential -- and many photographers prefer prime lenses to maximize image quality.  Finally, hand-held HDRs with lens and in-body stabilization are possible.

• Set exposure mode to full manual, metering to spot meter and drive mode to a high speed continuous drive setting.  Bracket settings will be established in the next section.

• Set aperture (Av) to a value appropriate for the scene and intended depth of field, e.g. f8.  This will remain unchanged during the bracketing sequence.

• Set ISO to a preferred value consistent with scene exposure value level (EV), minimum high ISO noise and required shutter speeds (to be determined below).  For most cameras, ISO 100 will yield the maximum DR and lowest noise.  Dim scenes may require a higher value in order to achieve useable shutter speeds if hand held.  Once fixed, this will remain unchanged during the bracket sequence.

The goal of the next step is to determine the maximum and minimum EV levels in the scene -- the brightness range -- prefereably using the camera's spot meter if it has one.  Zooming in to chosen sample areas and using a spot meter gives the most accurate measurements.  As a matter of personal preference, this may involve allowing specular highlights to blow out as well as allowing deep shadows to remain dark.  Absent a spot meter, a histogram can establish the points at which whites are saturated and darks are raised above zero exposure.  The brightness range, in turn, leads to bracket step size and number of exposures.

• Spot meter on the darkest area to be rendered with some detail.  Note the shutter speed value  (Tv).

  • With a zoom lens, zoom to maximum focal length to better isolate the metered area.  The same applies to metering the brightest area.

  • For overall dark scenes, increase ISO so that shutter speed is at least as fast as the hand-holding minimum for the intended lens focal length.

    • If a tripod is used the "minimum" shutter speed can be much lower than the hand held value.  Lens and in-body image stabilization can also lengthen hand held shutter speeds.

    • For bright scenes, shutter speed will have to be higher than the above minimum value to achieve exposures within the camera's range.

• Spot meter on the brightest area to be rendered without blowing out whites.  Note that shutter speed value as well.

• Calculate the steps of exposure difference between these two shutter speeds, △Tv.  This is the scene brightness range.

  • The fact that each of the above values was metered as 18% gray provides a margin of safety for the bracket exposures.

• If using a histogram to find brightness range and max and min shutter speeds:

  • First set shutter speed so that whites stop a bit short of touching the right limit of the histogram display.

  • Then note the shutter speed for which darks don't quite pile up at the left limit.

  • This provides limits analagous to the spot metering approach that are suitable for the next step.

• Split the difference between the bright and dark shutter speed settings.  The result will be the base EV0 shutter speed for the bracket.

• The brighness range must be included in the bracket set.  Specifics are user optional, but the following guidelines may help.

  • Choose a one-EV step size with three exposures if that covers the brighness range.

  • Otherwise use a two-stop step size with as many exposures as needed to fully contain the brightness range.  More exposures, using a one-EV increment, may produce a better HDR blend.

• Compose the image, focus on a selected object within the scene and make the bracket exposures.

The step size and number of images in the bracket should encompass the entire range of scene brightness.  A step size of one or two steps EV is usually recommended  For a small EV range ±1 EV may be sufficient.  Smaller bracket increments may increase blending quality.

After bracketed image have been captured, blend the images in an HDR program.  (We use three, Photomatix, Aurora 2019 and Capture One's Merge to HDR.  None bests the others on all images.)  The end product should result in whites being preserved while keeping as much of the darker end of the scene's DR as is preferred.

A final cautionary word. A well exposed bracket set will not necessarily blend to the envisioned HDR image. Each HDR program has different algorithms, controls and presets.  Blend results are bound to vary.  Typically, a small but exceptionally dark or bright area may be ignored in the blend.  Fortunately, some HDR programs provide tools to force inclusion of such areas.  Photomatix, for example, allows the user to mask a specific area of an individual image for mandatory inclusion in the blend.

© 2023 Michael W. Masters