By Lawrence Wee
HDR, or high dynamic range, images are created in a two-step process: the capturing of multiple images of a singular scene in the camera, and then off-camera processing. This article will address the first step, how you should take photos for HDR creation.
To make a good HDR image, the captured photo must be of high quality to begin with. And by "high," I mean of sufficient technical quality to meet the acceptance standards for stock photography.
While technology has been advancing to the point where we’re now getting enabled to create HDR in-camera (anyone see the new iPhone app?), for the moment, this is usually achieved off-camera with software. In film days, this high dynamic range problem was ameliorated by use of Graduated Neutral Density filters (GND). GND can be simulated digitally as well, and it is an alternative to HDR processing when your dynamic range requirements are not too large.
An Eye for Detail The first consideration is to recognize a “scene” that would make for a good HDR picture. Obviously, it is one where you want details in both the shadows as well as highlights, simultaneously -- which you would not be able to attain in a single shot with your camera.
Sunrise and sunset shots are often good subjects for HDR. Trees in deep shadows under a mid-day sun are also surprisingly good. I suppose there will always be new and surprising possibilities with every experiment. HDR has the ability to give a new look to a commonly appearing scene.
Setup The next issues to address are how many images to take, at what exposures, and at what EV interval between each. The most important aspect here is good exposures for shadows. The big drawbacks of HDR processing are high noise levels and artifacts, and these usually occur in the shadows. However, this can be helped, and overcome, if the shadows are well exposed in the captured image itself.
My routine starts with identifying the shadows and highlights in the scene, and then metering for these areas. I use the spot metering feature that is available on most cameras - I set the camera in aperture priority mode, say at f8 or f11, and then spot the highlights and the shadows, and, let's say, we get a reading of 1/30 for shadows and 1/800 for highlights.
I usually shoot at 1EV intervals. This is because the processing software I use seems to give the best results for intervals of 1EV and above. You may, of course, experiment to see if this is true for you as well. Also, I use the auto bracketing feature on my camera, which allows me a maximum of five brackets at 1 EV interval.
Based on this and the metered readings, I will set the camera up in Manual mode with focus lock, and five step bracketing centered on 1/125, i.e. I will take five rapid exposures at 1/30, 1/60, 1/125, 1/250, 1/500. I can live with some overexposure in the highlights. (I've pre-programmed a mode on my camera for this setup, only changing the aperture and center exposure [shutter speed] to be ready to shoot.)
Of course, if the scene has a higher dynamic range, you'll need a different bracketing solution, for example if shadows are 1/15 and highlights are 1/2000, then either take seven exposures - 1/15, 1/30, 1/60, 1/125, 1/500, 1/1000, 1/2000 - at 1 EV interval, or you have four exposures at 2 EV interval.
Capture The main purpose here is to minimize movements, both in the objects in the scene and in the camera itself. The capture should be as rapid as possible, minimizing the intervals between exposures. This will minimize the movements in the scene: clouds and water certainly can move significantly even within a second. To minimize camera motion, use such features as auto bracketing, tripod attachment, and cable or remote releases.
This is just one way to capture images optimal for the subsequent HDR generation process. It is not an end in itself. There will still be noise and artifacts after the HDR generation, but it will be at a level that further processing can almost totally eliminate.
This article was adapted from a Shutterstock Tips & Tricks tutorial.
More information on HDR:
- Read about Adobe Photoshop's "Merge to HDR" function
- Watch an Adobe video about how to process HDR images in Photoshop CS5.