Second Picture is devoted to original tutorials about 3D graphics, Photoshop, Photography and Web Design.
14.02.2008 Category: Photography Tutorials
Picture 1. HDR image is formed by merging several exposures.
This is a detailed guide about taking photos for an HDR image. Practice has shown that successful and smooth HDR photography takes careful planning and sets certain requirements for the gear.
The first part of this tutorial discusses photography gear. According to my knowledge it isn't possible to capture HDR photos with any of today's digital consumer cameras. Therefore the HDR image must be created by merging several normal photos. The idea is to take the same photo several times with varying exposures and merge them all to form one HDR photo. So in theory, the photos can be taken with any camera that allows manual shutter speed adjustment. The exposure between shots must be changed with shutter speed because changing the aperture would change depth of field.
Many modern cameras (point and shoot, bridge, slr) have several features that make it easier to photograph for an HDR image:
Photos taken for an HDR image should be similar apart from exposure. The following camera settings should be fixed in each shot:
The possibility to turn automatism off and adjust these settings manually is good for HDR photography.
Picture 2. Three bracketed photos with 2EV interval. (Notice that the example photo at the bottom of this HDR guide is made from 9 exposures.)
Exposure bracketing is a technique of taking several photos with varying exposures. A digital camera can change exposure in several ways. When it comes to HDR photography, its essential that exposure is controlled by shutter speed while keeping aperture and ISO sensitivity fixed. Other things to notice in camera's EB functionality are the amount of bracketed shots and the exposure interval. Many cameras only allow three shots with 1 EV interval. In my opinion that isn't enough for HDR photography. It's better if there is a possibility to bracket more shots or at least a possibility to increase the exposure interval. (Personally I take bracketed shots with Nikon D300 which is an ideal camera for this kind of work. Nikon D300 allows 2 to 9 shots with 1/3, 1/2, 2/3 or 1 EV intervals. I always bracket 9 shots with 1EV interval to make sure I capture the scene as well as possible.)
Continuous shooting means that the camera takes photos continuously while the shutter release button is held. Continuous shooting makes it possible to take bracketed shots automatically which makes HDR photography a little simpler. The faster the continuous shooting, the better the results. (Continuous shooting speed depends on the camera, storage and file format)
Timed continuous shooting makes it possible to take the bracketed shots automatically and by using timer. Timed shooting removes camera shake and makes the whole process easier.
To sum up, an ideal camera can use timer to automatically take many bracketed shots with adjustable exposure interval. This kind of functionality (like in Nikon D300) makes HDR photography pretty simple. Unfortunately there are only handful of digital cameras available that offer this good functionality for HDR photography. In an ideal camera, the user could define any exposure interval and any number of bracketed shots. Michael Reichmann (The Luminous Landscape) made a wish for this kind of functionality already in 2005.
Along with the camera, one should have a sturdy tripod and a lens hood to be well equipped for an HDR photography. Sturdy tripod makes sure the camera stays still while taking the bracketed shots. A tripod makes things easier but its possible, in bright conditions, to shoot even hand held. Photoshop is able to align the photos correctly even with some camera movement between the shots. If there is a lot of camera movement, the final HDR image must be cropped considerably and therefore good amount of resolution is lost.
HDR photography is well suited for high contrast scenes. High contrast scenes often include very bright areas such as light sources or reflections that might cause lens reflections. Its recommended to use lens hood to avoid as many lens reflections as possible.
The second part of this tutorial describes the process of photographing for an HDR image. Some might feel that HDR photography is complicated and time consuming. However, I feel that if you have the right camera, the hardest part is setting up a tripod and the rest is simple and fast.
I used the following gear with all example shots in this tutorial:
It's relevant to choose a scene with high dynamic range (high contrast). Low contrast photography doesn't really benefit from HDR technique because digital camera is able to capture the whole dynamic range with one shot. Besides the dynamic range, one should look for scenes without moving subjects. Many times moving subjects can be avoided by waiting. For example If you photograph nature, wait for the strong wind to calm down.
Picture 3. HDR photo made from 9 exposure with 1EV intervals.
It's important to understand that HDR technique isn't a magic that makes photos look good. In fact, HDR photo without digital image processing looks ugly. I'd like to emphasize that even though in HDR photography you must give a lot of thought to the technique and equipment, don't forget image composition!
Finally, fine tune your composition on tripod:
If your camera has exposure bracketing, you adjust the exposure just like you would with one photo. Finally the series of photos are taken by using the timer or by pressing the shutter release button.
Even though your camera would be missing the EB function, you can still do HDR photography. The series of photos can be taken manually by adjusting shutter speed after each shot. I think that about 1EV-1.5EV difference between exposures is good. The benefit of the manual photography is the possibility to take as many shots as you like. The downsides are possible camera shake and slower photography. If the series of photos is taken too slowly, even slow movement such as clouds, might cause problems.