The human eye has far greater ability to tell the difference between tones than most cameras. Ours eyes are incredibly flexible: they're capable of adjusting to see shadow and highlight details in the same scene. Your camera is not flexible in the same way. On a sunny day, you can look out a window and still see the interior of the room you’re sitting in. If you tried to make an image that matches what you’re eyes see you’d either blow the sky highlights to white (overexposure) or crush the details inside the room to black (underexposure).
Dynamic range is the measure of a photographic sensor's ability to record a variety of tones, from black to white. Cameras with the ability to record detail with a larger difference between maximum black and white—Dmin and Dmax—have a higher dynamic range. And digital cameras have steadily gained dynamic range and fidelity. Still, every camera is limited by the qualities it's the sensor.
High Dynamic Range
High Dynamic Range—or HDR—photography is one of the most popular kinds of computational photography and it’s designed to overcome the dynamic range limits of digital cameras. You combine multiple images of the same scene, each exposed slightly differently, to extend the dynamic range of your camera. For example, the highlight details are taken from one exposure or plate, and the shadow details are taken from another.
Creating a HDR image is a two step process. First you have to take the multiple exposures and then you need to blend them together using computer software like Adobe Photoshop, Adobe Photoshop Lightroom or Photomatix.
HDR photography can be quite controversial. If it’s done badly, the resulting images can look incredibly unnatural so some photographers dismiss the entire process out of hand. HDR photography, however, needn’t be done badly. If you approach it with care and consideration, you can create stunning images of scenes that are impossible to capture without it.
Andrew Childress and Ben Lucas have both explored the controversy surrounding HDR photography idea in more detail. If you don’t think HDR can be done well, check out their tutorials.
- Post-ProcessingHDR: Love it or Leave It?Andrew Childress
- HDRBusted! 7 Myths About High Dynamic Range PhotographyBen Lucas
Pre-Visualising the Scene
There is a time and a place for HDR photography. It’s a great technique if you’re shooting landscape images in dynamic lighting conditions but if you’re trying to create a portrait in a studio then it’s not going to be very useful. One of the most important skills to develop for HDR photography is recognising when it’s required and when it isn’t.
To do this you need to be able to assess the tonal range of the scene you’re trying to capture. You need to consider how dark the shadows are, how bright the highlights are, how you want them to appear in the final image and if your camera is going to be able to capture them to your satisfaction. If it’s not, then it might be time to use HDR.
Diana Eftaiha has looked at analysing the tonal range of a scene and how to pre-visualise the images that will result. Her tutorial is essential reading for anyone looking to get into HDR photography.
How to Capture HDR Images
Capturing HDR images is, in theory, very simple. You take a few photos of the exact same scene changing the exposure of each one.
The most basic HDR images normally combine three plates each a single stop a part; in one plate you expose for the shadows (blowing your highlights), in another you expose for your highlights (crushing your shadows), and in the third you expose for the midtones. If the dynamic range of the scene exceeds what three images can capture, you can use five, seven, or even more.
Generally with HDR images, the aperture and ISO remain constant while shutter speed is used to control the exposure of the frame. It’s possible to shoot HDR images with your camera hand held but a tripod makes it easier to keep the scene the same between each frame and means you can use slower shutter speeds.
Although you can calculate the exposure changes yourself, it’s far easier to let your camera, an external intervalometer, or even your smartphone do it for you. It means that you won’t have to touch your camera while it takes the pictures which prevents motion blur and keeps your images sharp.
At Envato Tuts+ we’ve covered a lot of the technical aspects of capturing HDR images. Peter Tellone has done a full overview of the process, David Appleyard has had a good look at exposure bracketing, and I’ve talked about controlling your camera with your smartphone to make HDR images.
- HDRHow to Shoot and Post-Process Professional HDR Photos in One DayPeter Tellone
- ShootingQuick Tip: How To Use Exposure BracketingDavid Appleyard
- Long ExposureTime-lapse and Long Exposure Control With Your SmartphoneHarry Guinness
Processing HDR Images
Some cameras can automatically merge a number of frames into a HDR image; unfortunately you don’t get much control over the process. It’s best to take the time to combine the different plates yourself using Photoshop, Lightroom, or a dedicated app like Photomatix or HDR Effex Pro.
The exact process for combining the different images depends on which program you use, although, for the most part it’s pretty automated. The software you use will take the areas with most detail from your frames and combine them into a composite image. You can control how realistic or surreal you want the final picture to be. Once you’ve combined the different plates into a single image, you can edit it as you would any other photo.
We’ve covered creating HDR images in a few different applications. Martin Perhiniak looked at using Photoshop a few years ago, while Andrew Childress covered Lightroom early last year. Simon Plant went into the most detail with his two-parter on Photomatix.
What software you want to use is up to you. All the different apps are capable of producing combining your different plates into awesome HDR images.
- Tools & TipsHDR Photography With Photoshop CS5Martin Perhiniak
- Adobe LightroomHow to Create High Dynamic Range and Panoramic Images in Adobe LightroomAndrew Childress
- Post-ProcessingExposure Blending in Photoshop & Photomatix: Part 1Simon Plant
- Post-ProcessingExposure Blending in Photoshop & Photomatix: Part 2Simon Plant
Different Kinds of HDR Images
As HDR photography has developed, related fields have grown more popular. In particular, long exposure HDR photography, HDR time-lapses and monochrome HDR photography. These styles of HDR all combine the high dynamic range techniques with other areas of photography.
By taking HDR techniques and using them in other photographic disciplines, it’s possible to produce really interesting results. On Envato Tuts+, I’ve looked at how to take long exposure HDR photos and Stefan Surmabojov has covered creating HDR time-lapses.
- HDRHow to Make a Long Exposure High Dynamic Range (HDR) PhotoHarry Guinness
- TimelapseCreating an HDR Time Lapse with SNS-HDR ProStefan Surmabojov
Conclusion and Recap
HDR photography is a great way to capture scenes with dynamic lighting that you would otherwise be unable to photograph. Bad HDR images are very obvious and have given the whole discipline and undeserved bad name.
A HDR image is a composite of multiple frames of the same scene, each with a slightly different exposure. Capturing the required images is normally done by changing the shutter speed between each shot. Any number of images can be merged together to create the final photo but three is the most common. Both Photoshop or Lightroom can handle the merging although there are also dedicated apps like Photomatix.
HDR photography isn’t just limited to landscapes: you can combine the techniques with almost any other form of photography! HDR time-lapses can be especially stunning.
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