HDR stands for High Dynamic Range and is a technique in photography where multiple images at different exposures are combined into one image using software. The number of images that you need depends on the difference between the lightest and darkest areas of the scene, you produce the images by bracketing exposures of the images, keeping the aperture constant and varying the shutter speed. This will produce images that range from the very dark to the very bright.
Taking HDR images
- Use the Auto Bracketing Mode of your camera, set to -2, 0 and +2. (In some cameras this is called Auto-Exposure Mode” or “Exposure Bracketing”)
- Depending on your camera bracketing can produce 3 to 7 exposures
- Use the Aperture Priority Mode of your camera, this will give you exposures at the same aperture but different shutter speeds
- Shoot in Raw not JPG, this will give you more flexibility
- Use a tripod when shooting in low light
- Use the lowest ISO possible
- When shooting hand held your minimum shutter speed should not be less than 1/focal length of your lens. If your lens has an image stabilizer you can use a lower shutter speed depending on how stops the stabilizer supports.
- Try to avoid movement in your images, if you have movement it can be fixed with software.
To create the HDR image, you need to have use software to merge the image into one image. Various photo processing software now have options to create HDR images, Photoshop has an HDR option, the latest version of Lightroom now has HDR option. There is also specialist software for creating HDR images, one that I use is Photomatix Pro.
The HDR image in this article was created from 5 images
When you merge the images into Photomatix Pro, it will produce a combined image. When importing the images into Photomatix Pro it will provide you with the following options
You can choose for Photomatix to do the following
- Align the images ( can choose between taken on tripod or hand held)
- Show options for ghosting
- Reduce Noise
- Reduce chromatic aberrations
When importing from lightroom you can also get the finished image to be reported into lightroom. There are two HDR processing options available
The main sliders for Tonal Mapping are
- Strength: controls the intensity
- Color Saturation: changes the intensity of the colours.
- Luminosity: controls the brightness
- Detail Contrast: changes the intensity of blacks and gives more texture.
- Lighting Adjustments: Smoothes the contrast between dark and light areas of image.
- Smooth Highlights: moving the slider to the right reduces the contrast in highlights (this can reduce the halo effect in some images).
- Gamma: flattens and brightens the image by moving the slider to the right, darken and increase contrast by moving it to the left
- White Point: adjust it to ensure that you don’t have any blown out areas
- Black Point: adjust it to keep some shadows dark.
- Micro-smoothing – adds micro-texture to the image, reduces noise and gives the image a more natural look when moved to the right.
The main sliders for Exposure fusion are
- Brightness: darkens or makes the image brighter
- White Clip: adjust it to ensure that you don’t have any blown out areas
- Black Clip: adjust it to keep some shadows dark.
- Color Saturation: to the right increases and to the left decreases the saturation.
Photomatix Pro has a number of presets that you can choose from, when you find a preset that you like you can then adjust the image using the sliders.
After you have finished in Photomatix you can chose to leave the image as is. If you feel that some parts of the image are over processed you can use the following advance techniques, using Lightroom, Bridge and Photoshop
Make Adjustments in Lightroom of the image taken at stop 0
Export the image to a folder and in the folder export the image from photomatix.
Using Adobe Bridge, select both images and from the Tools menu and import to Photoshop layers
In Photoshop, put the image from Photomatix as the top layer and then from the edit menu auto align layers
Select the HDR image layer and add mask layer, using a icon that looks like a black and white Japanese flag.
You can then use the brush to paint with black to bring the bottom layer through to the top layer, you can set the opacity to choose how much of the bottom layer goes through.
Then merge the layers to get a image with just one layer.
The final image then will look like this
Creating a HDR image from a single image
If you shot in RAW, you can create HDR images from a single raw file. In order to do this, you will need to create virtual copies of the image.
Selecting the copies and the original you can export to photomatix.
Photomatix will detect the images have the same exposure and offer the space the EV values to be in creating the HDR image
Then you can proceed as if the HDR image was created from multiple images
And the final HDR image