HDR as the name implies it stands for High Dynamic Range and for a photographer it means the range of light areas to dark areas in a photograph.
Often we come into situations where you find a gorgeous scene with high contrast that looks ecstatic with our eye, but when you photograph, you are not getting the same contrast as we saw with our eye.
You will find that shadow areas are loosing its detail in the photograph and comes very dark, and when you adjust camera exposure to make up that, the brighter areas are loosing its details and getting washed out.
There is a reason why this is happening. Our eyes has got great dynamic range and can see 11 stops of difference in light where as the camera can see only 5 stops difference in light. So when you get into a high contrast situation where your frame have highly bright areas as well as shadow areas, your eyes will able to see both correctly, but the camera fails to capture the same details as it has less dynamic range. This is where HDR photography comes handy.
In HDR photography, we take multiple photographs of the scene and each time the exposure is set differently for different areas of the scene and we combine these images with the help of software like Photoshop to make the final photograph.
Typically HDR photography needs a minimum of three photographs of the scene.
First, take the photograph of the scene in correct exposure for the camera’s metering, and in this case you will find the photograph may be loosing details on the brighter parts of the frame as well as on the shadow parts of the frame, but the mid-tones will be captured correctly and will be properly exposed.
Secondly, photograph scene again and this time adjust the exposure in the camera for capturing details on the brighter parts of the scene. The photo should have details of the brighter part of the scene, but you might see the image is greatly under exposed for the shadow areas.
Lastly, take the photograph of the scene exposing for the shadow area in the scene, and the photo should have great details of the shadow part of the image, but you may see the brighter parts completely washed out.
One of the easiest way to do this is by using the auto exposure bracketing feature in your camera.
By using the auto exposure bracketing, we can take shots at different exposure, like the one shown below. In the example, three photographs are taken, one with two stops underexposed, but shows details on the highlights, other with two stops over exposed, but it shows details on the shadow areas and lastly one with correct exposure.
Now we have three photographs, one exposed correctly for the highlights, one exposed for the mid-tones and one exposed correctly for the shadows. We can merge these photos using Adobe Photoshop’s ‘Merge to HDR Pro’ to create the final HDR image.
The software will ask you to select all photos and it will merge them to create one final composite image which will have the highlight areas taken from the underexposed image, the shadow details taken from overexposed image and the mid tones as in the correctly exposed image to generate the final image as shown below.
As the popularity of this imaging method grows, several camera manufactures are now offering built-in HDR features. If your camera has this, you don’t need any software. Just enable HDR feature ‘ON’ and camera will automatically take multiple shots based on your setting and generate the HDR image on the fly.
Also though we explained this photography method by taking with 3 images, you may need more images depending on your scene. The idea is to have correctly exposed images for each part of scene and merge them to generate the final image where everything is correctly exposed.
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