HDR:Explained

Does it ever occur to you that while taking photos in a dim environment using your smartphone,the photos often turn out to be blurry and full of noise. Also when the environment is too bright the images turn out to have a whitish tint(over exposed).
But turning on HDR mode on your phone always surprises you. What’s the mystery ?

What is Dynamic Range?

Dynmaic Range is the luminance difference between the brightest part and the darkest part of the image or its the ratio between the maximum and minimum intensities emitted from an object. Its a dimensionless quantity. The human eyes have a very high dynamic range, that is the human eye is highly efficient in comparing the luminance of the darkest blacks and the brightest whites.

What is f-number?

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Ever wondered what those tiny numbers engraved on the lens of your camera like f/2.0 mean? It basically depicts the amount of light entering the lens . Lower the number the more brighter the shot will be ,that is it will allow more light to enter. But wider apertures corresponding to lower f-numbers lead to a shallower depth of field. So lower the f-number ,range of distance that appears acceptably sharp will be lower.

HDR -High Dynamic Range

HDR is a technique which makes the image captured by your  camera more true to life by exposing the brighter and revealing more details of the darker areas of the image. This is done to compensate for the lower dynamic range of your camera.

How does it work?

High Dynamic Range photos are achieved by capturing the image multiple times at different exposure and brightness levels. Afterwards software processing is done to merge these images into a single image. This process reduces the noise and blur.

So if it is so good , should you always keep it on?

NO!!
HDR is supposed to make your pictures look better but it depends on when you use it. Sometimes HDR actually makes your pictures look worse. If any of your objects are moving then HDR will result in blurry images. As HDR captures multiple images so if the subject moves during this process then the image produced is blurry. HDR should also be not used when the colours are already vivid.It will wash them out.

File:HDR example-motion blur.jpeg

Verdict

HDR is designed to help you take better photos. It makes your picture look more colourful and vivid.The images produced by HDR mode are arguably better ,but its always dependent on software processing. Overall, I think HDR on  phones is gimmicky, as it’s being used to make up for deficiencies in the quality of the image sensor, but it does produce better photos.Once you get the hang of it, HDR can be a great tool for getting better pictures.
-Varun
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