By Max Therry:
You may already have heard of Automatic Exposure Bracketing, or AEB. Did you know that it could help you to get the best out of your High Dynamic Range (HDR) images?
In this article, we’re going to have a look at AEB – what it is, why we use it and where to find it on your camera. We’ll also have a look at how to merge your bracketed images to create a great HDR effect.
For those who don’t know, HDR images are a blending together of three or more photos of the same subject at different exposures. This allows for the full range of light and shadows to show up in the image.
Automatic Exposure Bracketing
To create your HDR image, you need to have a variation of exposures in the photos you’ll use to create your final image. The number of images used for HDR can go over five or more, but it’s best to start off with three – one underexposed, one correctly exposed, and one overexposed. You should always shoot in RAW file format for HDR images.
Here is how the brackets look like
You can do this manually, by adjusting your shutter speed one to two stops for each image, but it’s so much simpler to use AEB. This enables the camera to very quickly record three differently exposed images without you having to do anything. It can also help with the problem of ‘ghosting’ in HDR images. The camera records the three variations so quickly that there should be no real problems with movement in the image.
If you shoot in Aperture Priority Mode, you can select the aperture you wish to shoot at, and the AEB will adjust the shutter speed. You cannot shoot HDR images in Shutter Priority Mode, as you must keep your aperture and focal length exactly the same for each shot. You will also need to use a tripod to keep your camera steady whatever camera mode you use.
How to Use AEB?
To make things more complicated, each digital camera or phone camera has a different way of selecting the AEB function. Some, like the Nikon D70, have a button on the back marked BKT (bracket). Canon and some others have the AEB setting in their menus instead. Have a look in your camera’s instruction manual to find out where yours is, and how to set it up for what you want.
Most AEB controls will allow you to change the amount of variation between your bracketed images. These are called ‘stops’, and you can adjust them up or down. For instance, you may want a very large exposure range, so you would choose a 2 stop gap, or you might want a very small difference in exposure, so you’d choose a half stop gap. A good rule of thumb is to start with a 1 stop gap and adjust up or down from there.
Merging Your Images for HDR
Once you have your bracketed photos, you’ll need some specialist image editing software to prepare and merge your images for HDR.
If you already have a subscription to Photoshop CC, you can merge to HDR in there, or you can buy a HDR editor. Some can be used as plugins for Photoshop, such as Nik HDR Efex Pro, and some can be used as plugins or standalone programs, such as Aurora HDR or Photomatix.
All of these programs tend to follow a simple process for merging images to HDR. Once you have opened the program or chosen Automate-Merge in Photoshop, you will be prompted to choose the images you wish to merge.
Some of the programs will have an auto-alignment, remove chromatic aberration or reduce ghosting option. If these options are there, I would advise you to choose them as it lets the HDR software do all the hard work.
Once you have chosen your images and ticked your checkboxes, click ‘start’ or ‘merge’ and let the software do its thing. Depending on how big your RAW files are, and how many of them you are merging, it can take a little while, so have patience.
Once the software has finished merging your images, it will display the finished final image on the screen. It will have merged all the exposures so that you have detail in the shadows, midtones and highlights.
Some of the HDR software programs will let you make adjustments by fine-tuning the image. You can adjust the saturation, contrast, clarity etc, and some programs have a variety of overlays or filters to give your HDR images a different look. Have fun experimenting, but be careful not to overdo it – it’s easy to get carried away and then your image ends up looking like a garish cartoon!
Different HDR presets and filters
Once you are happy with your merged image, don’t forget to save it. Creating HDR images can be an addictive thing, and now you know how to use AEB it’s far simpler and quicker.Max Therry is an architecture student who is fond of photography and wants to become a professional photographer. He is also working on his photography blog about photo editing, modern photo trends, and inspiration. Feel free to reach him by email.