Have you ever wondered what that HDR toggle in your iPhone's camera options is for? And why you want to use it? HDR stands for High Dynamic Range and refers to a scene that includes both bright and dark elements -- the sun, reflecting off water, with deep shadows in the tree lines, or even a regularly lit person standing against the glare of an open window. When we talk about HDR photography, we are referring to taking photographs of such scenes. Unfortunately, unlike the human eye, camera sensors need a little extra help to get that done. So, in this week's iPhoneography column, we're going to discuss more details about HDR and how best use your iPhone's camera to get the most dynamically awesome photos ever.
As mentioned above, HDR stands for High Dynamic Range and is not exclusive to photography. When you step outside on a sunny day and view a scene that has both really bright area and very dark, shaded areas, you are living in a setting with a great dynamic range -- a huge range of light intensity levels. On a foggy day, the dynamic range is very low (and usually ideal for photography).
By definition, photography is the art of recording light. This act must be done with the camera sensor -- which is only capable of capturing a certain range of light intensity at any given time. Even the most expensive and most professional cameras on the market are not equipped with sensors that can capture all ranges of light in one photograph. That's where "HDR photography" comes in.
HDR photography is traditionally done by taking multiple photos with the exact same composition but with different exposure settings, then merging them all together as one photo. For example, a photographer will set up his camera on a tripod, take one photo that is exposed for the darkest area of the scene, a second photo exposed for the mid-range section, and a third photo exposed for the brightest area of the scene. The photographer will then edit these photos in sophisticated software, such as Photoshop, and blend them together so that all the properly exposed areas of the three photos are merged together as a single photograph. A quick search for "HDR" on Flickr will provide a lot of great examples of the types of photographs that are created with this technique.
The iPhone uses a similar, though less sophisticated, method of creating HDR images. When you enable HDR, the iPhone will take three photographs at the same time, with different exposures, and layer the best parts of each one to create one photo -- all in a matter of seconds. There are definitely noticeable improvements when using this feature, but it turns out that you can do more than just enable HDR to produce a better image.
Enabling HDR on your iPhone's camera is very easy. With the Camera app open, you should see a button at the top of the screen that says Options. Tap this button to see the Grid and HDR toggles. To turn on HDR, switch to toggle to ON by tapping it. Tap Options again to get the menu to disappear. HDR will stay on until you repeat the process to turn it off.
Since the iPhone will take three photos every time you trigger the shutter, Apple has included an option in the Settings app that lets you keep the normal photos -- meaning the photos you would've taken if HDR was turned off. To turn this on, go to Settings > Photos & Camera > Keep Normal Photo > ON.
Following the above instructions will have HDR up and running without any effort on your part. However, I've learned through much experimentation a little trick that will improve results -- exposing for the darkest part of the scene.
Everyone is familiar with the tap-to-focus feature of the iPhone's camera, but what many people don't realize is that not only is the camera focusing on your subject, but it's also exposing for this area of the photo as well. I don't have an explanation as to why, but exposing for the darkest part of the photo seems to produce better results than to let the iPhone choose an exposure automatically. The algorithm that the software uses appears to do a better job at recovering bright areas of a photo vs dark areas.
The sequence of photos shown above demonstrates this. The first photo was taken without HDR. The second photo was taken with HDR enabled and the exposure that the Camera chose automatically. For the third photo, I tapped on the left part of the screen where the grass is darkly shaded before taking the photo. It could be a matter of taste, but I prefer the last photo out of the three.
The built-in HDR feature of the iPhone's camera is a great, but there's no denying its limitations. That's where the App Store comes in. The App Store has a plethora of various apps dedicated to HDR iPhoneography that provides features like creating HDR effects on non-HDR photos from your Camera Roll, more sophisticated algorithms for merging photos, filters, and more. Here's just a few:
Do you have any favorite HDR app?
Now that you know all about HDR photography, go test your new knowledge on the streets! Or other beautiful scenic areas. As always, please share your best photos with us in the iMore Photography Forum. Most importantly -- have fun!